Drugs Used in Skin Applications

We know surprisingly little about the causes of many common skin disorders, for example eczema and psoriasis. Against such a background of ignorance it is not surprising that there are many myths about treatment and where there are many claimed treatments for a particular disorder there often is no specific treatment – otherwise we would all know about it and use it. This applies particularly to skin disorders.

However, we have seen great advances in the specific and effective cure of many infective skin disorders (see antibiotic and antifungal drugs). We have also seen the introduction of the corticosteroids, which have revolutionized the relief of many skin disorders. Other old-fashioned treatments continue, for example tar and dithranol, etc., and others such as the antihistamines have not produced the results hoped for, except in their specific and effective use by mouth in allergic rashes, particularly those due to drugs. Many skin treatments remain non-specific and at the very least they should not make the disorder worse. Yet the widespread use of antihistamines, local anaesthetics, antibiotics and antiseptics in skin applications have led to the production of allergic rashes, and the inappropriate use of corticosteroids has led to other problems (p. 211).

In the treatment of skin disorders the danger is that skin preparations containing potent drugs may be applied in too large a quantity to too large an area too often and over too long a period of time. You should be as sensible about applying drugs to the skin as you should be about taking drugs by mouth. Know what you are treating, know what you are applying and know the benefits and risks.

There are numerous skin applications available – creams, ointments, lotions, dusting powders, sprays, pastes. They are used for treating skin disorders in different stages of severity and in different areas of the body. For example, lotions (watery solutions) are used in acute skin conditions and where the skin is unbroken. Watery lotions act by evaporation and cool the skin. When used, they should be applied frequently. The addition of alcohol to a skin lotion increases its cooling effects. Lotions are useful for applying a drug in a thin layer over a large surface or on hairy areas of the skin. When the skin is broken an astringent (p. 217) may be included, as it helps to seal the weeping surface of the skin. Shake lotions are used for scabbed and dried skin disorders. They cool by evaporation and deposit a powder on the surface. Dusting powders (e.g. talc) are useful for treating skin disorders which affect skin folds – under the arms, in the groin, under the breasts. Creams moisten the skin more than ointments and cosmetically are more acceptable. Ointments are greasy and give more covering than creams; this occlusiveness helps to maintain the hydration of the skin. Ointments are more suitable for chronic, dry, scaly lesions. Pastes are stiff preparations and are useful for dry scaly patches.

The choice of the base for creams and ointments and other skin applications is often of equal importance to the choice of ‘active’ drug in the preparations. The base of a skin application (vehicle) can affect the degree of hydration of the skin and the ability of the active drug to penetrate the skin. Because of the complexity of formulation of many skin preparations it is important to be most careful about dilution which affects not only the effectiveness of a preparation but also its shelf life.

The groups of drugs most frequently included in skin applications and which are discussed in this chapter are:

1. Soothing skin applications – demulcents and emollients. These usually form the base or vehicle in which other drugs are included
2. Protective skin applications
3. Sunscreen and anti-sunburn skin applications
4. Corticosteroid skin applications
5. Antibacterial skin applications
6. Antifungal skin applications
7. Antiseptics and disinfectants
8. Anti-itching skin applications and drugs
9. Antihistamine skin applications
10. Local anaesthetic skin applications
11. Caustic and keratolytic skin applications
12. Astringent skin applications
13. Anti-perspirant skin applications
14. Deodorant skin applications
15. Other drugs used in skin applications.

1. Soothing Skin Applications

Demulcents

These are usually gums from stems, roots and branches of various plants, for example gum arabic, gum tragacanth, liquorice root, agar and sodium alginate (from algae). Synthetic drugs like methylcellulose are also used. Glycerin is a common constituent of skin applications and mixed with starch it forms a jelly base called starch glycerite. Glycerin should only be used in low concentrations because it can be irritant. Propylene glycol is related to glycerin and is used in lotions and ointments because it mixes with water (hydrophilic) and also dissolves in oils. Many other glycols are used to make water-soluble bases for ointments.

Demulcents are soothing because they coat the surface of the skin or mucous membranes (mouth, gums and throat) and protect the underlying area from the air and other irritating agents.

Emollients

Emollients are fats and oils which are soothing when applied to the skin. They soften the skin and are chiefly used as a base to which other active drugs (e.g. antibiotics) are added. They soften the skin by forming an oily film over the surface of the skin, thus preventing water from evaporating from the surface cells and so keeping them moist.

Emollient skin applications contain vegetable oils, animal fats, paraffin and related chemicals, and waxes.

The vegetable oils are usually cotton-seed oil, corn oil, peanut oil, almond oil and cocoa-bean oil. Animal fats are wool fats from the wool of sheep. These are of two types – wool fat (anhydrous lanolin) and hydrous wool fat (known just as lanolin) which is wool fat mixed with 20 to 30 per cent of water. Wool fat can produce skin allergies. It is not used as often as it used to be and yet the message is still given that there is something magical about preparations that contain lanolin.

Paraffin-related preparations include mineral oil (liquid paraffin), white petroleum, and yellow petroleum (e.g. Vaseline is a brand preparation of white and yellow petroleum jellies). Waxes are principally obtained from beeswax (yellow wax). White wax is bleached beeswax. Spermaceti is a waxy substance from the head of the sperm whale which was used to raise the melting point of ointments to stop them melting too easily when applied to warm skin (cold creams), particularly in hot climates. It was replaced by jojoba oil in 1982 in most countries. Jojoba oil comes from the beans of the jojoba bush, a native of Northern Mexico and Southern California.

2. Protective Skin Applications

Protectives are applications used to cover the skin and mucous membranes, in order to protect them from contact with an irritating agent. They are by definition insoluble and inactive and cover the skin physically rather than having any chemical effect. They include dusting powders which are used to protect the skin in certain areas (e.g. skin folds) and on the surfaces of ulcers and wounds. They are smooth and prevent friction, and some absorb moisture from the surface of the area to which they are applied (for example, ones containing zinc oxide or starch). On open wounds they make a crust and those containing starch have to have an antiseptic added to stop the starch fermenting. Dusting powders often contain talc (which is mainly magnesium silicate) and of course talc is widely available as talcum powders.

Mechanical protectives such as collodion were used to close off small wounds but it is now considered better to let the air get to a wound. Petroleum gauze and gauzes impregnated with antibiotics are useful as protective dressings to wounds although the tendency now is to use dry non-adherent dressings. Barrier creams are used to protect the skin against irritants which are water-soluble. They usually contain dimethicone (silicone) or a related silicone. These adhere to the skin and have water-repellent properties. They are available as ointments and sprays as well as creams. They provide protection against the irritating effects of soap, water, skin-cleansing agents and breakdown products from urine. They may be useful in preventing bed-sores and nappy rash. They should not be used on inflamed or damaged skin, or near the eyes, because they may produce irritation. They may produce allergic skin reactions.

3. Sunscreen and Anti-sunburn Skin Applications

The health-promoting properties of sunlight have long been recognized but it is only in the past fifty years that sunbathing for cosmetic reasons has become fashionable. And it is only in more recent years that the harmful effects of solar radiation and ultra-violet light from artificial sources have become recognized. Excessive exposure to the sun’s rays without appropriate protection is harmful: it causes burning and ageing of the skin, cancer of the skin, and cataracts.

Sunburn and suntan are caused by ultra-violet rays (UVR). The shorter ultra-violet waves (UVB) cause the burning and contribute to long-term changes in the skin that cause cancer and ageing. The longer waves (UVA) cause the tanning. They do not cause sunburn but they are involved in allergic reactions to the sun’s rays and also in long-term damage to the skin which is associated with ageing and skin cancer.

Tanning results from migration of the brown pigment, melanin, from the base layer of the skin up into the surface cells. This provides some protection against sunburn but the main protection comes from a thickening of the surface layer of cells.

The acute effects (sunburn) and the chronic effects of the sun’s rays on the skin are directly related to the total dose of UVR received by the skin, i.e. by the intensity, duration and frequency of exposure. Protection is offered by the melanin content of the skin and the capacity of the skin to produce new protective melanin on the skin surface (i.e. to tan).

Sunscreen Preparations

Sunscreen preparations have an important function in so far as they can protect the structure and function of the skin from damaging rays. They are chemicals in the form of clear or milky solutions, gels, creams or ointments which reduce (filter out) the harmful rays. They work by absorbing, reflecting or scattering the rays. The selection of a skin application should depend upon your liability to sunburn and to tan.

Sunscreens for application to the skin are either chemical sunscreens or physical sunscreens. Chemical sunscreens contain one or more UVB absorbing chemicals which filter off the harmful rays. They are usually colourless and must be non-irritant and non-staining. Frequently used products include aminobenzoic acid, padimate, benzyl salicylate and mexenone. However, they do not protect against UVA, the long-term effects of which may take 10–20 years to appear.

Physical sunscreens are usually opaque formulations and contain particles which reflect and scatter the harmful rays (both UVA and UVB). They include titanium dioxide, talc, zinc oxide, kaolin, ferric chloride and ichthyol. They are essential for people who are ultrasensitive to the sun’s rays. Physical sunscreens tend to melt in the heat of the sun.

In recent years preparations containing methoxypsoralen (bergapten) or bergamot oil (which contains methoxypsoralen) have been heavily promoted. The application of these formulations actually stimulates tanning (melano-genesis) which may provide improved protection but they can produce sunlight sensitivity with subsequent pigmentation. Their association with an increased risk of skin cancer has not been proved.

Sun Protection Factor (SPF)

This is a measure of the effectiveness of a sunscreen preparation. It is the ratio of the time taken for UVB rays to produce redness of the skin through a sunscreen preparation compared with the time taken to produce redness without any sunscreen application. For example, an SPF of 6 means a person should be able to stay in the sun six times longer without burning.

Factors that Influence the Sun Protection Factor (SPF)

These include the subject (skin type, age, amount of sweating, skin site), the UV intensity (season, weather, reflection), radiation source (the sun, type and age of lamp), concentration of sunscreen application, the base (vehicle) used in the preparation, the thickness of the application, effect of water (e.g. after swimming), environment (temperature, humidity, wind) and sweating. In addition, the testing procedure is very important because the effectiveness of a sunscreen preparation out of doors may not be related to its performance indoors (i.e. under laboratory conditions).

The most important consideration when purchasing a sunscreen preparation is how you react to sunlight. Buy a preparation that protects against both UVA and UVB and that suits your requirements and one that is manufactured by a reputable company. Most sunscreens should be reapplied after swimming and repeatedly during prolonged sunbathing. Avoid sunbathing at midday (11.00 a.m. to 3.00 p.m.).

Sunscreens do not stimulate tanning. Increased tanning is caused by the activation and proliferation of the pigment cells in the skin (melanocytes). This process will be decreased by the application of effective sunscreens.

Patients suffering from sensitivity to sunlight (photosensitivity) often require combination therapy with two sunscreen preparations, the first application in an alcoholic solution which evaporates and then a second application of a cream on top.

Adverse Effects of Sunscreens

Certain sunscreen formulations containing aminobenzoic acid may cause selective burning (smarting) and occasionally contact or photo-dermatitis. Patients allergic to sulphonamides and certain local anaesthetics (benzocaine and procaine) may have allergic reactions to aminobenzoic acid. Patients on sulphonamides or thiazide diuretics may cross-react with aminobenzoic acid and develop dermatitis.

* Details on package should include degree of protection against both UVA and UVB rays. Note: ‘Star’ rating refers to ratio of UVA and UVB protection. Four stars indicate that the product offers a balanced amount of UVA and UVB protection. Three, two and one stars indicate that the product offers proportionally more protection against UVB than UVA.

Oral Treatment of Photosensitivity (Sensitivity to Sunlight)

The effectiveness of most orally taken drugs has never been proven. They include beta-carotene (a precursor of vitamin A) which is a natural constituent of many plants including oranges, carrots and tomatoes; and anti-malarial drugs (e.g. chloroquine) which have been used for many years to provide protection in patients sensitive to sunlight.

Quick-tanning Preparations

These applications, which contain drugs such as dihydroxyacetone (DHA), do not stimulate the production of the tanning pigment in the skin; rather they stain the skin yellow-brown. It offers no protection to sunlight. The dye lawsone is no more effective.

The use of ‘tanning’ tablets which contain canthaxanthin merely colour the skin and underlying fat orangey-brown. It is used to colour foods and medicines. All products containing canthaxanthin have been withdrawn because of the risk of eye damage.

Sunburn

There are several treatments for sunburn; among the commonest are calamine lotion and zinc lotion. Applications containing a corticosteroid (see below) can be very effective. Do not use applications containing an antihistamine because they may produce an allergic rash and usually in sunburn there is a fairly large area of skin to be treated.

Drug-induced Sunlight Sensitivity (Photosensitivity)

This means the skin is excessively sensitive to the sun’s rays and goes red and burns very easily. It may be due to a drug; for example, a tetracycline or a sulphonamide antibiotic; griseofulvin; a phenothiazine; an oral anti-diabetic drug; a thiazide diuretic; nalidixic acid; an oral contraceptive drug; gold; diphenhydramine (an antihistamine) and, rarely, saccharin.

Drugs applied to the skin may also sensitize it to sunlight, for example, tar (the basis of tar and ultra-violet ray treatment of psoriasis) and hexachlorophene, an antiseptic present in numerous skin applications and toiletries. Various deodorants may also sensitize the skin, and so too may sunscreen applications (e.g. aminobenzoic acid ).

The important thing to remember is that if you burn more quickly than usual for you, then always think – is it a drug I am taking or a skin application I am using? Stop any of these immediately and check whether they produce sunlight sensitivity.

Some people are actually allergic to sunlight and can develop severe dermatitis on exposed parts of their skin (photodermatitis). Certain disorders may produce sunlight allergy, for example porphyria (a disorder of metabolism). If you develop a rash on the exposed parts of your skin, always consult your doctor.

4. Corticosteroid Skin Applications

If you read about corticosteroids in Chapter 37, you will learn that they reduce inflammatory reactions. For this reason they are widely used to treat many skin disorders, in order to reduce the redness, soreness, swelling, pain and irritation which often characterize such conditions. Corticosteroids are present alone or in combination with other drugs in numerous skin, eye and ear applications prescribed by doctors. They are very effective. However, they do not cure but only suppress the symptoms, so that if the underlying skin dis-order is not self-limiting, or if the causative agent is not removed (for example, contact dermatitis caused by an article worn on the body), it will flare up again when the corticosteroid preparation is stopped. This is known as a rebound effect.

Corticosteroids available for use on the skin vary in potency and therefore concentrations included in skin preparations vary from 0·001 per cent for triamcinolone up to 2·5 per cent for hydrocortisone. The popularity of any particular preparation may reflect more on the results of vigorous sales promotion rather than on any clear differences in effectiveness.

Adverse Effects and Precautions

Corticosteroid skin preparations are not curative and if treatment is suddenly stopped the skin condition may flare up. They are of no use in treating nettle-rash (urticaria). Prolonged use may produce thinning of the skin particularly when used on the face, flexures (knees and elbows) and on moist parts of the skin. They may also produce soreness and irritation at the site of application, irreversible ‘stretch marks’, increase growth of hair, contact dermatitis, acne, mild depigmentation and sometimes a dermatitis around the mouth in young women.

They should not be used to treat acne rosacea or acne, dermatitis around the mouth, scabies, leg ulcers, TB, ringworm or viral skin disease, or untreated bacterial or fungal skin diseases. Extensive and/or prolonged use in pregnancy should be avoided. They are of no use in urticaria (nettle-rash) and generalized itching (pruritus). The more potent the corticosteroid the more risk there is of adverse effects. Clobetasol is very potent, betamethasone is potent, clobetasone is moderately potent and hydrocortisone is mild. Because of the risk of stunted growth and skin damage potent corticosteroids should not be used in children and the others should be used with utmost caution. Only a mild corticosteroid should be used on the face (1 per cent hydrocortisone) and not for more than 5 days. Use for no longer than 5 days in children. Potent corticosteroids should only be used in adults for a few weeks and then switched to mild ones. The general rule is to use the least powerful corticosteroid in the lowest strength for the shortest duration of time.

In using corticosteroid skin preparations it must be remembered that when inflammation is reduced the resistance to infection is lowered and secondary infection may occur. This is particularly likely to happen when corticosteroids are used under occlusive (e.g. plastic) dressings. This may cause boils, thrush and other infections to develop. Allergies may also occur to additives in corticosteroid applications and this should always be considered if there is a poor response to treatment.

Long-continued use of corticosteroids under plastic dressings may produce a local wasting of the deep layers of the skin to produce a flattened, depressed, stripy-looking area. This may take many years to go away. Corticosteroids applied to the skin may enter the blood circulation and produce harmful effects. (See Chapter 37.) This is particularly likely to happen with children (who may also lick the ointment off the skin) and in adults using very large amounts.

Do not forget also that corticosteroids can delay the healing of ulcers (e.g. leg ulcers). Finally, it is important that you should not borrow skin ointments containing a corticosteroid drug from a neighbour or friend – different disorders and different people respond differently.

Some skin disorders can get infected and become soggy with pus (e.g. infected eczema). In these infected skin disorders the use of an application containing a corticosteroid and an anti-infective drug (e.g. an antibiotic) may be very effective. Such a combination is also useful on skin rashes in areas where infection is likely to occur, for example, in the groin or around the anus. But do not forget that there is a slight risk that an anti-infective drug may produce an allergic reaction which the corticosteroid will mask. Remember this if a skin rash seems to be getting worse despite the fact that initially it improved with such a preparation.

The wrong use of such combinations in primary infective skin disorders may produce very severe effects. For example, if they are used to treat impetigo (a bacterial infection of the skin) a small localized patch may be turned into a serious widespread skin infection; a simple fungus infection (e.g. athlete’s foot) may spread over a large area; and herpes simplex (cold sores) may produce nasty ulcers.

Corticosteroids mixed with an antibiotic, antifungal drug, or an antiseptic, may be used where the primary skin condition would be expected to respond to corticosteroids but where there is an added infection (e.g. infected eczema). The choice of preparation is not critical. Such simple principles as not too much for too long should apply, and if the disorder gets worse stop the treatment and see your doctor.

5. Antibacterial Skin Applications

When a skin infection is superficial (e.g. impetigo) an antibiotic skin application can be dramatically effective. If the infection is deeper in the skin surface (e.g. cellulitis), then local applications of an antibiotic will be useless and you will need an antibiotic by mouth or injection.

When the sulphonamides and penicillin were introduced, doctors used them liberally in skin applications and produced many allergic reactions in their patients. Not only were these allergic reactions inconvenient for the patients, they were positively dangerous for some. They sensitized the patient to the drug, with the consequent risk of a severe allergic reaction if that patient had to be given a sulphonamide or a penicillin by mouth for some more serious infection. Another problem was the development of resistant organisms.

To minimize these risks antibacterial drugs should be used on the skin that are not used by mouth or injection. Application to large areas of skin may produce general adverse effects, for example, neomycin, gentamicin, colistin and polymyxin B may damage hearing, particularly in children, the elderly and patients with impaired kidney function.

Antibacterial preparations only used topically include framycetin (Soframycin, Sofra-Tulle), mupirocin (Bactroban), neomycin (in Cicatrin, Graneodin), polymyxin B (in Polyfax), colistin (Colomycin) and silver sulphadiazine (Flamazine).

Antibacterials also used by mouth and injection include chlortetracycline (Aureomycin), fusidic acid (sodium fusidate, Fucidin), gentamycin (Cidomycin), metronidazole (Anabact, Metrogel, Noritrate, Rozex, Metrotop, Zyomet) and tetracycline (Achromycin).

Antibiotic skin applications should be used for as short a period as possible over as small an area as possible, and if the disorder gets worse they should be stopped immediately.

6. Antifungal Skin Applications

Before reading this section it is useful to read the chapter on antifungal antibiotics (Chapter 47). Here you will learn about the antifungal drugs which may be used locally and by mouth. Some of these have revolutionized the treatment of fungus and yeast infections. Rarely they may irritate the skin and cause allergic reactions.

There are many effective antifungal skin preparations and they vary only in their activity against specific fungi. They include amorolfine (Loceryl), clotrimazole (Canesten, Masnoderm), econazole (Ecostatin, Pevaryl), ketoconazole (Nizoral), miconazole (Daktarin), sulconazole (Exelderm) and tioconazole (Trosyl). Other effective antifungals include amorolfine (Loceryl), nystatin (Nystaform, Nystan in Tinaderm-M), terbinafine (Lamisil) and tolnaftate (in Tinaderm preparations). Other less effective antifungals include the undecenoates (e.g. in Monophytol, in Mycil, Mycota), benzoic acid (in Whitfield’s ointment), benzoyl peroxide (in Quinoped) and salicylic acid (in Phytex).

7. Antiseptics and Disinfectants

There is quite a mix-up between the terms antiseptic and disinfectant. In general the term antiseptic is used to describe those drugs applied to the skin or other parts of the body in an attempt to prevent infection. The term disinfectant is used to describe a chemical applied to objects in order to destroy germs. However, the term disinfectant is often used to describe both uses. Antiseptic preparations applied to the skin are sometimes called germicides. Antiseptics may kill or prevent the growth of bacteria, fungi and viruses. Some disinfectants are used as antiseptics in reduced strengths but some are too irritant and some antiseptics are not strong enough to use as disinfectants.

Antiseptics and disinfectants belong to various chemical groups which can make the choice look very complex and confusing. In fact most doctors learn to use one or two preparations (often by their brand name). The choice is not critical and the need to use such preparations in the home is greatly over-emphasized in the advertising media.

Some Main Chemical Groups to which Antiseptics and Disinfectants Belong

Chlorine and chlorine-releasing substances. Chlorine kills germs and the most commonly used chlorine-releasing chemical is sodium hypochlorite. This is present in commonly used preparations such as Chlorasol and Milton. Others include chlorinated soda solution (Dakin’s solution) and chlorinated lime (this is often mixed with boric acid solution as in Eusol).

Detergents. These include quaternary ammonia compounds such as benzalkonium, cetrimide, cetylpyridinium and domiphen. The most commonly used antiseptic detergent is cetrimide which is present in numerous preparations and Drapolene which contains benzalkonium and cetrimide. An important point to remember about these preparations is that soap can reduce their activity. They are also prescribed as shampoos by doctors for the treatment of scurfy disorders of the scalp.

Phenol and related drugs. These lose their effects fairly quickly when diluted. They include phenol, cresol and thymol. Solutions of these should not be applied to wounds since they can be absorbed into the blood-stream and can be very toxic.

Chlorinated phenols. The two most widely used of these include a chloroxylenol (Dettol), and hexachlorophene (e.g. Ster-Zac). Hexachlorophene may very rarely produce brain damage when applied extensively to the skin of premature babies. It may produce skin sensitivity and also make the skin sensitive to sunlight. Chlorocresol is another example of a chlorinated phenol.

Iodine compounds include weak iodine solution, povidone-iodine, (e.g. Betadine and Savlon Dry Powder). These preparations may produce skin sensitivity and interfere with the function of the thyroid gland.

Dyes. There are two types of dyes used as antiseptics:

(1) Acridines, which include acriflavine, aminacrine and proflavine. These are slow-acting but work in the presence of pus and damaged tissues, which inhibit the effects of some antiseptics. In high concentration they may delay wound healing and may produce skin sensitivity.

(2) Dyes such as brilliant green, gentian violet and malachite green. These are derivatives of triphenylmethane and were widely used before the introduction of antibiotics and antifungal drugs.

Formaldehyde. Formaldehyde and related drugs may be used as disinfectants, but not as antiseptics because they irritate the skin.

Chlorhexidine. Chlorhexidine (e.g. Hibitane) is frequently used as an antiseptic. It may occasionally cause skin sensitivity and it is inactivated by soap and by cork (so it should not be kept in a corked bottle).

Other chemical groups. These include alcohols (e.g. ethanol, benzyl alcohol, methylated spirit, surgical spirit), oxidizing compounds (e.g. benzoyl peroxide, hydrogen peroxide), salts of heavy metals (e.g. mercury and silver) and acids (e.g. acetic acid ).

Choice of Antiseptic and Disinfectant

Chlorine-releasing substances such as sodium hypochlorite (e.g. Domestos, Milton) or chlorinated phenols (e.g. Dettol) are perfectly suitable as disinfectants, but do not forget that chlorine acts as a bleach (e.g. Domestos). For cleaning the skin a detergent such as cetrimide (e.g.Tisept) is useful and so are chlorinated phenols (e.g. Dettol, hexachlorophene (Ster-Zac) and chlorhexidine (e.g. Hibitane)). Mixtures of cetrimide and chlorhexidine are also available and providone-iodone (e.g. Betadine) is useful. Salt solution is also useful for cleaning the skin.

8. Anti-itching Preparations

There are many causes of itching (pruritus). These may be in the skin, such as allergic skin rashes, eczema, nervous rashes, scabies and body lice. In these disorders scratching may give relief, but often leads to the skin being damaged and further itching. In elderly patients the skin may degenerate, producing itching. Some drugs, e.g. morphine, may produce itching. Kidney disorders, liver and gall-bladder disorders and diabetes may also produce itching. Therefore, it is important for you to be examined by your doctor if you have an itching disorder because it is better to treat the cause than to treat the itch. There are two main approaches to the drug treatment of itching but generally treatment is disappointing.

1. Skin Applications

These may contain antiseptics (p. 214) in very low concentrations, for example, phenol, benzyl alcohol, balsam of Peru, chlorbutol. However, these may irritate the skin and produce allergic rashes. Local anaesthetics in low concentrations are not very effective and may irritate the skin and produce skin allergies. Antihistamine creams (p. 217) are useful for small areas (e.g. insect bites) but are not recommended for large areas because they too may produce allergic skin rashes. Other drugs such as menthol and camphor are also used. Emollients are useful if itching is associated with a dry skin.

Crotamiton (Eurax) may be useful in some patients, but it should not be applied to broken skin. Calamine lotion is probably just as effective. Corticosteroid skin applications (p. 211) are used to treat itching in eczema.

2. Drugs by Mouth

There are two main groups of drugs which are taken by mouth to relieve itching. These are the antihistamines and the phenothiazines. One commonly used drug from the antihistamine group is trimeprazine (Vallergan).

The severe itching which accompanies obstructive jaundice may be relieved by a male sex hormone, for example, testosterone, which may also be helpful in senile pruritus. Cholestyramine may help in liver and gall-bladder disease because it reduces the blood level of bile salts, which is high in these disorders; it is thought that they are the cause of the itching.

Caution should be applied to the use of antihistamines and phenothiazines in the elderly, because they can quickly become confused under an apparently ‘normal’ dose of any of these drugs. Simple skin applications should be tried first, such as calamine lotion or an emollient cream.

9. Antihistamine Skin Applications

Skin applications that contain antihistamines are sometimes of use in treating small, acute, irritating and painful skin lesions such as an insect bite or nettle-rash. Their regular use and their use on large areas should be avoided because they can produce allergic skin rashes. Antihistamine skin applications available include diphenhydramine (in Caladryl), antazoline (in RBC, Wasp-Eze ointment) and mepyramine (Anthisan, in Wasp-Eze Spray).

10. Local Anaesthetic Skin Applications

The widespread or regular use of skin applications containing a local anaesthetic is not recommended because of the risk of producing irritation of the skin and allergic rashes. They should not be used in young children because of the risk of absorption into the blood-stream.

Preparations available include tetracaine(amethocaine) (in Anethaine), benzocaine (in Antisan Plus, in Burn-Eze, in Lanacane, in Solarcaine, in Wasp-Eze Spray) and lidocaine(lignocaine) (in Dermidex, in Dettol Antiseptic Pain Relief Spray, in Vagisil Cream).

11. Caustic and Keratolytic Skin Applications

Caustics are drugs which are used to destroy tissue at the site of application. If it causes a scab by precipitating protein from the damaged cells then it is also called a cauterizant or an escharotic. Surgeons use electric needles to burn (or cauterize) the ends of small bleeding blood vessels.

Some commonly used caustics are acetic acid, phenol, podophyllum, trichloroacetic acid and silver nitrate. They are used to treat warts and corns.

Keratolytics are included in some skin applications because they loosen the surface cells of the skin and cause them to swell and go soft so that they can easily be cut off. They are used to treat warts, corns and acne and include benzoic acid and salicylic acid and their salts, benzoyl peroxide and resorcinol.

12. Astringent Skin Applications

Astringents are drugs which act on the surface of cells to precipitate protein. They do not enter the cell and therefore they do not kill the cell but they make its surface less permeable to water, etc., and so it dries up and shrinks. They are included in skin applications and have the effect of hardening the skin, drying up soggy areas of damaged skin and reducing minor bleeding from skin abrasions. Astringents in various dilutions may be used in throat lozenges, mouthwashes, eye drops, ear drops and in preparations used to treat haemorrhoids; as caustics (for burning off dead tissue, etc.); and in the past they have been used to treat diarrhoea. They are now widely used in antiperspirant sprays and applications (see below). The main ones used are salts of zinc and aluminium and tannins.

Alum (potassium aluminium sulphate powder) has been used as an astringent

218 · Medicines: A Guide for Everybody

to treat sweating sore feet, to shrink the stump of the umbilical cord and to treat skin abrasions, small cuts and ulcers. Dried alum (burned alum) was even more astringent than alum. Aluminium acetate solution is a useful astringent lotion and is also used in ear drops. Aluminium sulphate is a strong astringent and may be used as a mild caustic; so may silver nitrate. Hamamelis is another astringent used to shrink haemorrhoids and hamamelis water (witch hazel) is used as a cooling application on sprains and bruises. Krameria is also used to shrink haemorrhoids and is included in some throat lozenges. Zinc chloride is used as a caustic, astringent and deodorant. Zinc sulphate is used as an astringent, particularly in eye drops. Calamine is used as a mild astringent.

Aluminium acetate and zinc acetate are mild astringents of choice but it really depends on what is being treated – sweating feet or a small abrasion, haemorrhoids or a leg ulcer.

13. Anti-perspirant Skin Applications

These are available in every size, shape and colour of container, as pads, sprays, roll-ons and creams, with every possible smell, to be applied to an ever-increasing number of parts of our bodies (male and female).

The drugs most commonly used as anti-perspirants include salts of aluminium and zinc. Some may stain fabric, some are acidic and irritate the skin, and some are soluble in alcohol and may be used in sprays and aerosols. Those anti-perspirants which contain an aluminium salt may produce an allergic skin rash in sensitive skins. The mechanism of action of anti-perspirants is unknown but they are considered by some experts to be astringents.

14. Deodorant Skin Applications

Like anti-perspirants the market is flooded with deodorant preparations. They reduce the number of bacteria that live on the skin. Since these bacteria break down sweat to produce products that have an unpleasant odour, their reduction produces a reduction in body odour. Antiseptics such as hexachlorophene and benzalkonium are frequently used in deodorant preparations. Hexachlorophene may produce allergic skin rashes on sensitive skins, and benzalkonium and related complex ammonia compounds are inactivated by soap and can irritate the skin in concentrations above 1 per cent. Some deodorants contain antibiotics which can also cause allergic reactions and sensitize the individual to their future use. In addition, people may become allergic to the fragrances used in these preparations.

Remember – if you develop a rash in the areas where you apply a deodorant or anti-perspirant, consider that it may be an allergic reaction and stop the application immediately.

Drugs enter the blood-stream more easily from mucous surfaces such as the vagina than they do from the skin and therefore they should be used with caution, particularly by pregnant women. Vaginal deodorants are best avoided because they may cause irritation and bladder trouble (urethritis and cystitis) – stick to water.

15. Other Drugs Used in Skin Applications

Allantoin is used in preparations to treat psoriasis; e.g. Alphosyl lotion contains allantoin and coal-tar extract in a non-greasy base. It is also used to treat cracked nipples and nappy rash in Massé cream.

Cade oil is used in preparations to treat eczema and psoriasis.

Calamine is used as a mild astringent in creams and lotions, and in dusting powder.

Dithranol is used in small concentrations in ointments and pastes to treat psoriasis and other long-standing skin disorders. It can burn and stain the skin brown and cause allergic rashes in sensitized patients.

Ichthammol is slightly antibacterial and it irritates the skin. It has been used in skin applications to treat chronic skin disorders (e.g. eczema), and mixed with glycerin it was often used as an application on superficial thrombophlebitis, on abscesses and in infections of the ears.

Potassium hydroxyquinoline is used to treat bacterial and fungal infections of the skin. It has been used as a deodorant and appears in Quinoderm cream, used to treat acne.

Salicylic acid is used to treat hardened skin and corns.

Selenium sulphide is used to treat dandruff and other scalp disorders. Starch is used in dusting powders.

Sulphur is a mild antiseptic and has been used to treat acne and other disorders.

Talc is used as a dusting powder.

Tar is used to treat eczema and psoriasis.

Zinc oxide is used as a mild astringent and as a soothing agent and protective.

These drugs appear in numerous proprietary preparations for the treatment of many skin disorders. Read details about them in the A–Z of Medicines.

Drug Treatment of Some Common Skin Diseases

Acne

Acne vulgaris (referred to as acne) usually starts at puberty. At this age, the oil-producing glands surrounding hair roots (sebaceous glands) become active under the influence of male sex hormones (androgens), which are produced by the testes, and the adrenal glands in both males and females. Production of these hormones increases up to about the age of twenty-five years, after which it levels out. People who get acne do not have higher levels of male sex hormones than people who do not develop acne and it may be that their sebaceous glands are more sensitive to male sex hormone stimulation.

Acne vulgaris affects the sebaceous glands in the skin of the face, neck, middle of the chest and back. These are areas where these glands are most active. Although acne is related to the production of male hormones, it occurs only slightly more commonly in males than females. We do not know why some people get acne and others do not, or why some just get mild acne and in others it is severe.

In acne, the outlets from grease glands get blocked by skin cells and debris and this forms what are called blackheads (or comedones). The glands then swell up and become infected and inflamed, to produce the red lumps (papules) and yellow lumps (pustules) of acne. If the outlet is blocked completely the glands may swell right up to form a cyst and some individuals may get an overgrowth of scar tissue (called keloid) which produces irregular lumps and bumps in the affected area.

Treatment of Acne

There is no specific treatment for acne and it is often best to use what suits you or to try different treatments, but do not be persuaded to use expensive preparations when the simplest and cheapest may be the best.

The important part of treatment of acne is to keep the skin free from grease by regular cleaning. Ordinary soap and water may be all that is needed. If this does not work, then a detergent solution such as cetrimide should be used.

Drying and Peeling Preparations

In addition to keeping the skin clean and free from excess grease it may be necessary to apply preparations that dry and peel the skin and stop black-heads from forming. The most frequently used chemical is benzoyl peroxide which is present in many preparations. It not only dries and peels the skin, but also has antiseptic properties. Salicylic acid produces similar effects. Azelaic acid (Skinoren) peels the skin and has antibacterial effects. It can be used when benzoyl peroxide does not work.

Vitamin A Derivatives

Isotretinoin (Isotrex, in Isotrexin) and tretinoin (Acticin, Retin-A) are related to vitamin A. They are applied as a cream, gel or lotion. They are useful in some patients with moderately severe acne, but may produce redness and peeling for several days. Too frequent use may cause dermatitis. They should not be applied to the eyes, up the nose or on the creases of the mouth. The acne may appear worse at first and it may take up to four weeks before improvement occurs. Isotretinoin may also be taken by mouth (see later).

Adapalene (Differin) is a retinoid-like drug which may be less irritant than isotretinoin or tretinoin.

Abrasive Preparations

Abrasives may be used to help peeling and cleansing of the skin and some individuals may occasionally find these of benefit. They include Brasivol (fine particles of aluminium oxide in a paste) and Ionax Scrub (polyethylene granules with benzalkonium in a gel).

Antibacterial Preparations

A tetracycline antibiotic (e.g. tetracycline: Topicycline) applied to the skin may help to reduce bacterial infection in the sebaceous glands and may possibly produce some anti-inflammatory effects. Other antibiotics included in acne applications include clindamycin (Dalacin T solution) and erythromycin (Eryacne, Stiemycin, with zinc acetate in Zineryt, with benzoyl peroxide in Benzamycin).

Because of the risk of producing bacterial resistance to antibiotics use a topical preparation for no more than 10–12 weeks with a few weeks’ rest and use a non-antibiotic (e.g. benzoyl peroxide) when possible. Alcoholic preparations of an antibiotic should not be used with benzoyl peroxide.

Antiseptic Preparations

Hydroxyquinoline kills bacteria and fungi and is included in some acne preparations. It may produce irritation and redness.

Sulphur, which is used to produce peeling, also possesses some antiseptic effects. It is no longer considered beneficial in treating acne.

Anti-inflammatory Preparations

A topical application of nicotinamide (a vitamin B compound) may help to relieve inflammation.

Warning: Greasy creams or ointments and corticosteroid applications may make acne worse.

Drugs Taken by Mouth to Treat Acne

Antibiotics

Bacteria that ‘normally’ live in the oil-producing glands may produce irritant substances from the oil which cause inflammation. Antibiotics (e.g. tetracyclines) which dissolve in fat can kill these bacteria and help to reduce the inflammation. Therefore, if the acne is moderate or severe, or does not respond to local applications, it is worth adding an antibacterial drug by mouth such as doxycycline, minocycline, tetracycline, or erythromycin. The antibacterial drug must be taken daily. Maximum improvement usually occurs within 4–6 months, but sometimes treatment has to be continued for a longer period. Oral antibiotics should not be given at the same time as a topical antibiotic because of the risk of producing bacterial resistance.

Tetracycline antibiotics should not be used in pregnancy (see p. 237), therefore women taking a tetracycline daily by mouth for the treatment of their acne should avoid getting pregnant while on treatment.

Long-term use of antibiotics applied to the skin and/or taken by mouth may cause a superinfection of the skin around the nose and central part of the face, causing redness and pustules. This superinfection is often difficult to treat, and the treatment should be based on trying to identify the infecting micro-organism, testing its sensitivity to antibiotics and using the appropriate antibiotic.

Hormones

Male sex hormones are associated with the development of acne and female sex hormones (oestrogens) may therefore reduce some of their effects. Obviously oestrogens cannot be used in males, and because of the risks of oestrogens they should not be used alone in females. However, a combination of an oestrogen with a progestogen reduces the risks and therefore a combined oral contraceptive may help acne in some women, but high oestrogen-containing contraceptive pills may make acne worse.

Cyproterone is an anti-male sex hormone and combined with an oestrogen (ethinyloestradiol) it may be beneficial in women who suffer from severe acne and who wish to take an oral contraceptive. The combination product is marketed under the name of Dianette.

Vitamin A Derivatives

Isotretinoin (Roaccutane), a vitamin A derivative, is effective in some patients with severe and nodular acne and may prevent scarring. It reduces oil production and helps to unblock hair follicles, alters bacterial growth in the sebaceous glands and produces peeling of the superficial layer of the skin. It is best used in individuals who have failed to respond to antibiotics by mouth and/or who have severe deep acne.

It may produce serious harmful effects and therefore any possible benefits need to be weighed against the risks. It should only be used when other treatments have failed and only under specialist supervision.

Athlete’s Foot (Tinea Pedis)

Athlete’s foot is ringworm of the feet. Scrapings from the infected area should be examined under the microscope in order to confirm the diagnosis of a fungus infection before treatment is started. An effective treatment is a local application of an antifungal drug such as clotrimazole (Canesten), sulconazole (Exelderm), miconazole (Daktarin), or econazole (Ecostatin) ointment. If one of these does not work and the infection is severe, griseofulvin (Grisovin) tablets by mouth should be added to the treatment and taken for 6–8 weeks. Compound benzoic acid ointment (Whitfield’s ointment) is fairly effective but messy to apply.

Baldness

Regaine is a solution of minoxidil which is used to stimulate hair growth in male-type baldness in men and in women who develop a diffuse thinning of the hair. During the first few months of treatment there is very little regrowth and it takes up to twelve months to see any benefit. Fewer than half of males and about one-third of females develop an acceptable growth of hair. Best results in men are obtained on a small patch of balding on the crown which has been present for only a few years. An important limitation of this treatment is that if daily applications are stopped the baldness becomes as extensive as if it had never been treated. The new growth of hair will be shed within two or three weeks of stopping treatment. For adverse effects, see A–Z of Medicines.

Chilblains

Chilblains are caused by cooling of the hands and feet and/or the whole of the body in susceptible individuals. They affect mainly toes and fingers and are caused by constriction of the small arteries in the fingers and toes on exposure to cold, followed by dilation of the arteries which results in swelling of the skin with itching and burning.

The best treatment for chilblains is prevention – central heating, warm clothes and physical exercise.

Drugs used to improve the circulation (see Chapter 27) should not be used, and any ointment that produces a redness and burning because it irritates the skin or dilates the arteries may do more harm than good. High doses of calcium or vitamin D have not been shown to be of value. No drug treatment can be recommended, whether by mouth or applied locally to the chilblains. Try to prevent them, but if you develop chilblains just apply a simple greasy ointment (e.g. Vaseline) to protect the skin.

Dandruff

Dandruff is caused by an overgrowth of yeasts at the hair roots. It is worse at puberty. Any detergent shampoo is of use in treating dandruff. If used at least two or three times a week a detergent shampoo will keep the hair clear, but of course a detergent shampoo will not prevent the growth of yeast cells.

The scalp should be well massaged, the shampoo left in contact with the scalp for several minutes and then thoroughly washed off. Any shampoo left on the scalp may cause the dandruff to stick together and be even more visible. Detergents used in shampoos include sodium lauryl sulphate, benzalkonium and cetrimide.

Shampoos that contain drugs to treat dandruff are often referred to as medicated shampoos. Certain drug additives are included in shampoos because they may reduce the production of cells from the skin of the scalp, dissolve the particles of dandruff or break them up into smaller pieces, relieve itching and/or act as an antiseptic.

Pyrithione zinc has antibacterial and antifungal properties and is a useful treatment for dandruff. Selenium sulphate is probably no better than a detergent shampoo. It should not be applied within 48 hours of hair colouring or a permanent wave preparation. The antifungal drug ketoconazole (in Nizoral shampoo) will help to kill the yeast cells. Ketoconazole and zinc pyrithione are active against pityosporum ovali an organism implicated in seborrhaeic dermatitis of the scalp. Topical lithium may also be beneficial.

Preparations which break up and loosen dandruff particles contain keratolytics. They dissolve the cement that holds the cells together. They include sulphur, salicylic acid and allantoin.

Tar products break up the dandruff but they smell and they may stain the skin and hair. They also make the skin sensitive to sunlight. They are useful for treating psoriasis of the scalp.

Cresol, thymol and phenol are commonly used anti-infective drugs included in shampoos. They may irritate the scalp and are of very doubtful benefit.

Dermatitis and Eczema

The terms dermatitis and eczema have the same meaning – a superficial non-infective inflammation of the skin which may be acute, sub-acute or long-lasting (chronic). When acute, the skin is red, swollen, blistered, weeping, crusted, scaling and often itching. Scratching and rubbing may cause bleeding and scarring. When it is chronic, the skin may be dry, thickened, scaling, itching and scarred.

In the United Kingdom the term eczema is used to describe dermatitis caused by a sensitivity to some factor from inside the body (for example, allergic dermatitis caused by food allergy) and the term contact dermatitis is used to describe dermatitis caused by contact with some factor outside the body (e.g. dermatitis to a cosmetic).

Atopic eczema (atopic dermatitis) is a chronic eczema that usually occurs in individuals with a family history of allergic disorders (e.g. eczema, hay-fever, asthma). Atopy means an inherited tendency to develop eczema, asthma and/or hay-fever in response to certain substances taken into the body by mouth or breathed in. The cause is unknown but it is considered to be an abnormal allergic response.

Contact dermatitis is an acute or chronic inflammation of the skin caused by substances in contact with the skin. It often occurs in well-demarcated patches. It may be caused by a direct irritant (irritant dermatitis) or by an allergic reaction (allergic dermatitis).

The appearance of irritant and allergic contact dermatitis is very similar, but an allergic reaction may be more red and there may be more small blisters (vesicles) and swelling of the skin.

Contact with irritants may damage normal healthy skin and cause an existing dermatitis to flare up.

Allergic contact dermatitis is caused by a delayed allergic reaction to some substance. The skin first becomes sensitized by contact with the substance, which triggers off a delayed allergic response. This may not appear for days, months or even years, despite the fact that the individual’s skin may have been in direct contact with the substance daily – for example, make-up, or an ointment for eczema.

Treatment of Acute Inflamed Dermatitis and Eczema

If the lesions are acute and wet, then wet soaks containing an astringent such as aluminium acetate may help. If there is a risk of infection, an antiseptic soak such as potassium permanganate may be beneficial.

To relieve the inflammation and itching a powerful corticosteroid cream should be used for the first few days and then a milder preparation should be substituted. Only hydrocortisone cream should be used on the face because others may cause harmful effects on the skin (see p. 211). If the condition is severe and extensive it may be necessary to add a corticosteroid by mouth for a few days. An antihistamine by mouth may help to relieve itching.

If infection is present a combined corticosteroid/antibiotic cream should be used. If the infection is severe it may be necessary to use an antibiotic by mouth after a swab has been taken to identify the infecting micro-organism. For very severe resistant atopic eczema an immunosuppressive drug such as cyclosporin (Neoral, Sandimmun) may help. See Chapter 17.

Treatment of Dry, Scaly Dermatitis and Eczema

Over a period of time the irritated skin becomes thick, scaly and itchy, resulting in much scratching. Dry, scaly patches are best treated with a soothing skin application (an emollient) which will soothe the skin and make it less dry and scaly.

A mainstay of treatment, particularly in atopic eczema, is the use of short causes of a mildly or moderately potent corticosteroid ointment, but see adverse effects and precautions on p. 211.

When the skin is very thick and scaly it may help to use a substance that peels the skin, such as salicylic acid, coal tar or ichthammol.

The essential fatty acid (gamolenic acid) in evening primrose oil is available in capsules (Epogam, Efamast) to treat atopic eczema. It may possibly be of benefit in some children.

Insect Bites and Stings

The area should be cleansed and cooling lotion applied (e.g. calamine lotion). Bee stings should be removed by scraping with a fingernail or knife before cleaning. If the reaction is fairly severe an antihistamine should be taken by mouth. An application containing hydrocortisone may be very effective in relieving the itching and soreness.

Most over-the-counter preparations used to relieve the symptoms of an insect bite or sting contain one or more of the following: a counter-irritant such as camphor or menthol, a local anaesthetic such as benzocaine an anti-histamine, a skin protectant such as zinc oxide or calamine, an antiseptic such as cresol. All these may possibly help, but some may irritate the skin and produce other problems.

Lice

Body Lice (Pediculosis Corporis)

These lice are spread from person to person by direct contact or by contact with clothing. Lice and eggs can be found in the clothing. The patient itches and scratches and should be bathed and given clean clothing. An aqueous solution of malathion or carbaryl should be applied all over the body, left on for 12 hours or overnight and then washed off. This treatment should be repeated after one week. Calamine lotion with 1 per cent phenol will reduce the itching.

Crabs (Pediculosis Pubis)

This infestation affects pubic and armpit hairs and causes severe itching. In adults it is spread by close sexual contact. The underclothes should be washed and the infected person should take a bath and then apply an aqueous solution of malathion or carbaryl to the affected area and to all parts of the body as well. The lotion should be left on for twelve hours or overnight and then washed off. This treatment should be repeated after one week.

Note: It may also be necessary to treat beards, eyelashes or moustaches if these have become infested.

Head Lice (Pediculosis Capitis)

Head lice are spread by direct person-to-person contact and by contact with infected combs and hats. It is a common infestation among schoolchildren. Infestation may occasionally cause itching but usually all that can be seen are nits (eggs) on the hair shafts. The nits mature in about three to four days and the lice can then be found at the back of the head and behind the ears.

Treatment includes the use of preparations containing carbaryl (Carylderm), malathion (Derbac-M, Prioderm, Quellada M, Suleo M), permethrin (Lyclear), or phenothrin (Full Marks). In order to prevent resistance most Health Authorities rotate these treatments.

Lotions should be used in preference to shampoos because the latter are not in contact with the hair long enough to work properly.

Lindane is no longer used because there are now strains of treated lice which are resistant to it. However, resistance is also developing to the other agents and their use should be monitored.

Warning: Water-based (aqueous) preparations should be used in asthmatics and very young children in order to avoid alcoholic fumes given off by preparations that contain alcohol. Contact of 12 hours or overnight is needed to kill the nits.

Daily shampooing and wet combing with a fine comb is probably as effective as using a pesticide and it is much safer.

Psoriasis

The skin is continually being renewed and as dead cells are shed from the surface, new cells underneath take their place. This process maintains the normal surface of the skin (the epidermis). However, in psoriasis the process is disturbed and in certain areas of the skin new cells are produced at an excessive rate while the shedding of old cells remains normal and cannot keep pace with the number of new skin cells pushing out on to the surface. As a result these new cells pile up to produce patches of thickened skin covered in silvery scales. The patches heal over without producing a scar.

The spread and extent of these patches of psoriasis vary between acute and chronic attacks, and are affected by the age of the patient. Patches of psoriasis may differ in size from a fraction of an inch to large sheets affecting the skin of the whole of the trunk. Psoriasis may affect the fingernails, scalp, skin folds, elbows, knees, palms of the hands, soles of the feet, the back and the buttocks. The eyebrows and the skin around the anus, genitals and the navel may occasionally be affected. It may also be associated with arthritis affecting a few or many joints (psoriatic arthropathy).

There is no cure for psoriasis, but treatment can provide effective control by reducing the size of the patches and reducing inflammation. Treatment varies according to the severity and extent of the psoriasis and the areas affected.

Treatment of Acute Psoriasis

Acute psoriasis that comes on in childhood (acute guttate psoriasis) usually clears up on its own in two or three months and sometimes treatment may actually make it worse. All that is needed is a simple emollient cream.

Treatment of Mild to Moderate Psoriasis

For mild psoriasis a soothing ointment (emollient) may be all that is necessary. If it is moderately severe, then it may be worth trying a coal tar product at night and an emollient in the daytime. An application of dithranol for half-an-hour in the daytime may be added to the treatment. In addition, a corticosteroid application and/or an anti-itching application may be used. Exposure to the sun’s rays may help, but sunburn should be avoided because psoriasis may develop at the site of any damage to the skin.

Skin applications work better if the thickened scales are removed first. This is often best achieved by having a daily bath containing an oil emulsion and then rubbing off the scales using a bland cream.

Coal tar products are antiseptic, they relieve itching and they help the loss of scales, and so does salicylic acid. They are useful for treating chronic patches of psoriasis.

Dithranol should be used with caution because it may irritate the surrounding skin. A ring of Vaseline should therefore be applied around the patch of psoriasis before applying the dithranol. It may stain the skin and clothing black. It works just as well if it is left on for about 30–60 minutes and then washed off or it can be left on all night. Low concentrations of dithranol should be used to start with and then the concentration gradually increased. Fair-skinned people are more sensitive to dithranol than dark-skinned people. Dithranol is messy and it is better to use a brand preparation such as Dithrocream or Micanol.

The use of both tar and dithranol on the face should be avoided because they may irritate the skin. Their use should also be avoided in skin folds because they may cause boils to develop. In these areas an emollient should be used.

Bland emollient creams are the applications of choice to stop itching. Local anaesthetics and antihistamine preparations should not be used because they may produce irritation and allergy.

Calcipotriol (Dovonex) is a synthetic vitamin D. It is used in ointment form to treat mild to moderate psoriasis. It stops the overgrowth of cells in the surface (epidermis) of the skin that occurs in psoriasis and helps to restore a normal turnover of the surface cells. It has less effect on calcium metabolism in the body than other synthetic vitamin D preparations (e.g. calcitriol) and therefore the risk of a raised blood calcium, calcium in the urine and bone softening are reduced. Unlike dithranol and tar it does not have an unpleasant smell and it does not stain the clothing.

Applications which soften the skin and help it to peel work by loosening keratin, a protein in the outer layer of the skin. They include sulphur, salicylic acid, allantoin and resorcinol. However, they are irritant and should not be applied over large areas since they may be absorbed, producing harmful effects.

Corticosteroid applications may be beneficial. However, they may lose their effectiveness if used every day for more than two or three weeks. It may therefore help to alternate treatment every one or two weeks between a corticosteroid and an emollient.

Adverse effects of corticosteroid applications on the skin are discussed earlier. They may be absorbed into the blood-stream and produce harmful effects. This is particularly likely to happen if they are applied under adhesive or plastic dressings; if they are applied to large areas of the body; if highly concentrated and/or potent forms are used, and/or if large amounts are applied at regular intervals.

The strength and number of applications of a corticosteroid should be gradually reduced as the treated patches of psoriasis improve. Hydrocortisone is the only corticosteroid that should be applied to the face. Thick patches of psoriasis which are resistant to applications may be injected under the skin with a solution of a corticosteroid such as triamcinolone. Such treatment should not be repeated within about three weeks in order to avoid wasting of the skin.

Severe and/or Chronic Psoriasis

The treatment of severe and/or chronic psoriasis follows fashions, but some old-fashioned treatments are still in favour – for instance local applications of coal tar, dithranol and skin softeners (e.g. salicylic acid). These are usually applied after a bath and after rubbing off the scales.

Ultraviolet B radiation is the basis of a treatment called Ingram’s method. It consists of a warm bath containing a tar solution, a dose of ultraviolet radiation to produce redness, and then the application of tar or dithranol paste to the patches of psoriasis.

The tar and dithranol make the patches of psoriasis sensitive to the ultra-violet radiation. Repeated every day this treatment is effective, and in most patients it clears up patches well in about 3–6 weeks.

Methoxypsoralen and other psoralen drugs act on DNA in cells to slow down their rate of division. The drugs are activated by exposure of the skin to ultraviolet radiation. Methoxypsoralen is used in a treatment referred to as PUVA treatment (P stands for psoralens and UVA stands for ultraviolet A radiation). PUVA treatment is used to treat large chronic patches of psoriasis.

The methoxypsoralen is used as a bath solution or given by mouth and this is followed by ultraviolet treatment two hours later – timed to coincide with peak concentrations of the drug in the blood-stream. Treatments with gradually increasing doses of UVA are repeated two or three times a week until the psoriasis has cleared up. An average of about twenty treatments are usually required. The rash may not return for several months, but if necessary the skin can be kept clear with one PUVA treatment every one to three weeks.

Warning: PUVA must be used with caution because of the risk of burning and long-term risks of cataracts, premature ageing of the skin and skin cancer.

Methotrexate is a drug used to treat cancer. It stops cells dividing and because of this action it has been found to be useful in some patients suffering from severe chronic psoriasis, but because of the risks it should only be used under hospital supervision to treat psoriasis that has not responded to any other treatment. Other drugs of this type that have been tried include hydroxyurea and azaribine. So has the immunosuppresant cyclosporin (see p. 75).

Etretinate: Although vitamin A is involved in skin development and function it has proved of no use in treating psoriasis. However, etretinate, which is related to vitamin A, reduces scaling and improves psoriasis. It slows down the rapid rate of cell division in skin cells and reduces the production of keratin – the hard protein that forms the outer layer of the skin. Unfortunately, serious risks may easily outweigh any benefits.

Acitretin (Neotigason) is a breakdown product of etretinate in the body and it has replaced etretinate in the treatment of psoriasis. It should not be used in pregnancy and patients should avoid getting pregnant for two years after treatment has stopped.

Tacalcitol (Curatoderm) is related to calcitrol (vitamin D3). It binds to vitamin D3 receptors in the keratin-making cells of the skin and slows down their division. It is used as an ointment to treat plaques of psoriasis.

Scabies

Scabies is due to an invasion of the outer layer of the skin (the epidermis) by a mite called Sarcoptes scabiei. The infection is spread from person to person by close skin contact (e.g. by holding hands, or sleeping together). Successful infection is caused by a fertilized female mite burrowing into the skin, where she lives for the rest of her life. As she burrows along the skin she lays her eggs every day for several weeks. The eggs hatch in a few days and the larvae leave the burrows and shelter in hair roots, where they develop into adult mites. They then mate and set the whole cycle going again, which takes about two weeks.

The mites burrow into the skin, particularly on the hands and feet, and after about a month an itchy rash develops at the infected sites because the individual has become sensitive (allergic) to the mites. The rash characteristically affects the wrists, ankles, fingers, buttocks, abdomen and genitals. It does not occur above the neck in adults. With any future infestation itching will start almost straight away because the individual has become allergic. An infected person may scratch so much that the skin is damaged and dermatitis may develop, which may also become infested.

Treatment

Drugs used include:

malathion (Derbac M, Prioderm, Quellada M, Suleo-M)

permethrin (Lyclear)

It is absolutely necessary to treat every member of the household who may have skin-to-skin contact, whether they are itching or not. It is also important to treat sexual partners.

After washing well, an application of malathion or permethrin should be applied all over the body from the neck downwards, preferably with a paintbrush and by some other member of the household. Particular attention should be paid to the webs of the fingers and toes and under the nails. The scalp, neck, face and ears should be treated in children under two years of age and in the elderly and those who are immune-deficient due to disease (e.g. AIDS) or drugs (e.g. chemotherapy). Lotions and solutions are easier to apply than creams and ointments.

Washing thoroughly is now recommended in preference to a hot bath, which may increase the absorption of the drug into the blood-stream and possibly increase the risk of harmful effects. Aqueous preparations should be used because alcoholic ones may irritate scratched skin and the genitalia.

Benzyl benzoate (Ascabiol) is occasionally used but it is irritant and should not be used in children.

Warts

There are thirty-five types of viruses that cause warts. Warts may appear at any age but are commonest in children. They may be single or multiple. They may disappear without treatment in months or years and they may recur at the same site or at different sites. Patients who are immune-deficient due to drugs or disease (e.g. AIDS) may suffer from an extensive attack of warts.

The common types of warts often affect the hands and feet. The latter are often referred to as plantar warts or verrucae.

Most wart applications contain a caustic or keratolytic, which removes the keratin layer and destroys the underlying layer of the skin. Commonly used ones include salicylic acid, formaldehyde and podophyllin. Most of these preparations will irritate the surrounding skin and since warts clear up on their own it is not necessary to subject little children to such treatments. Because the ‘life’ of a wart is self-limiting, it also explains the success of various folk remedies and the ‘charming away’ of warts. Any treatment that is applied when the warts are disappearing on their own will be considered to have caused their disappearance!

Simple remedies are best (e.g. salicylic acid collodion (Cuplex, Duofilm, Occlusal, Salactol, Salatac, Verrugon). An adhesive plaster should be put over the warts after the application has dried.

Stronger preparations containing formaldehyde (Veracur) or glutaraldehyde (Glutarol) may work on some plantar warts in some people, but their effectiveness is difficult to predict. Preparations containing formaldehyde or glutaraldehyde may irritate the skin and cause allergic rashes. They also have an unpleasant smell. Formalin solution (3 per cent) used as a foot soak may help multiple plantar warts, or a tape impregnated with 40 per cent salicylic acid may be helpful if it is kept in place for several days at a time. Skin specialists may burn some warts with liquid nitrogen, or they may surgically remove large and ugly warts.

Podophyllum preparations are useful for treating genital warts but they can produce severe irritation of the skin and serious adverse effects if applied too heavily. They should not be used in pregnancy. Preparations include podophyllin paint compound and podophyllotoxin (Condyline, Warticon).

Imiquimod (Aldara) cream is used for the treatment of external genital warts.

Posalfilin, which contains podophyllin resin 20 per cent and salicylic acid 25 per cent, is suitable for treating plantar warts (verrucae). The application should be applied directly on to the wart or warts and contact with the surrounding skin should be avoided because it may irritate. A sticking plaster should then be applied over the treated wart and left in place until the next treatment is due – treatment is usually given once or twice daily. Dead skin should be removed with a pumice stone before the next application.