The nose, sinuses, throat and air passages are lined by a membrane of mucus-producing cells (a mucous membrane) which is very richly supplied with blood vessels which ensure that the air we breathe is warm and moist.  The blood supply increases when the air is cold and decreases when the air is warm.  In addition, the surfaces are covered with tiny hair-like structures (cilia) and by a moist coat of mucous.  The cilia and mucous have a very important function because they clean the air that we breathe by trapping dust and other particles, including bacteria, and propel them out to the surface so that they can be coughed up and spat out or blown out of the nose.  The mucous contain chemicals that kill bacteria and viruses.  It also contains antibodies and white blood cells which move out from the bloodstream to engulf and destroy micro-organisms. 

An increase in mucous production occurs if the surfaces become inflames as a result of an infection (e.g. a cold), by allergy (e.g. hay fever) or by irritation (e.g. inhaling irritant vapours or dust).  Mucous production may be interfered with by some cold and cough remedies that dry up the surfaces and of course by dry atmospheres and smoking.  Therefore, an important part of treating coughs and colds is to keep the surfaces moist by drinking more fluids than usual, stopping smoking if you smoke, and avoiding dry atmospheres if possible.  In addition, the inhalation of steam may help.

Colds

A common cold (coryza, infectious rhinitis, acute rhinitis) is caused by one of many different types of cold viruses.  They are principally spread by droplet infection, as a result of infected people coughing and sneezing.  They produce inflammation of the nose (rhinitis), sore throat (pharyngitis), a hoarse voice (laryngitis), inflammation of the windpipe (tracheitis) and, occasionally, bronchitis.

The onset of a common cold is sudden, with sneezing, running nose, sore throat, smarting eyes and sometimes headache and mild feverishness. Colds are expensive to society because more time is lost from school and work due to colds that to all other disorders added together; yet we do not know how to prevent colds or what makes some people get more colds than others.  We do not have a cure and we do not know how to shorten the duration of a cold.  Whether we fill ourselves up with drugs or not, it will take 5-7 days for our body defences to get rid of the infection.

Colds are costly

Clearly we feel very sorry for ourselves when we have a cold, which probably explains why we spend millions of euro each year on cough and cold remedies.  It is very big business: manufacturers of cold remedies also spend millions of euro every year on advertising in order to persuade us to take their product to relieve our aches and pains, dry up or unblock our noses, relieve our sore throats and/or stop our tickling coughs.  We are very vulnerable to theses pressures and feel better for taking some remedy, particularly if it smells looks and/or tastes as if it could do us some good.

To treat or not to treat

In making a decision whether or not to take a cold remedy, it is important for you to understand that any cold remedy relies on the use of only a small number of active drugs which are used in varying doses and combinations.  These are aimed at four groups of symptoms – reducing aches, pains and feverishness; relieving blocked and/ or runny noses; relieving sore throats; and relieving coughs.

Relief of aches, pains and feverishness

Aches and pains are good warning signs that you may have an infection and that you should rest.  The fever that you get with a cold is usually very mild and there is no evidence that such a mild fever is harmful but, on the other hand, there is no evidence that it is beneficial, although there is a probability that fever may help the body’s defence system against infection.  Nevertheless, aches, pains and feverishness are unpleasant and can easily be relieved.  However, remember that if you relieve these symptoms with drugs you have done nothing to affect the underlying infection and although you may feel better, you should still take it easy for a few days and not do heavy physical work.

To relieve aches and pains and feverishness, aspirin, ibuprofen or paracetamol are very effective if used singly and in an appropriate dose.  Despite this fact they are often mixed with other drugs in numerous cold remedies, which is unnecessary.

Preparations that contain pain relievers such as codeine, dextropropoxyphene or dihydrocodeine are not necessary because these drugs are not as effective as aspirin or paracetamol in relieving the aches, pains and feverishness of a cold.

For treating aches, pains and feverishness, it is better to stick to a single preparation of aspirin or paracetamol.  Do not take mixtures.  Tablets of aspirin BP or tablets of paracetamol BP are the cheapest preparations to buy. Paracetamol is the drug of choice, especially if aspirin upsets your stomach, if you have asthma or chronic bronchitis, haemophilia, if you are taking anti-coagulants (anti-blood-clotting drugs), if you are allergic to aspirin, or if you suffer from ulcers, heartburn or chronic indigestion.  It is the drug of choice in children under the age of 16 years.

WARNING:  Do not give aspirin to children under the age of 16 years; use paracetamol instead.  Do not take aspirin along with alcohol.

For a common cold you will need to take no more than three standard doses of paracetamol or aspirin during the first 24 hours of your cold at intervals of no less than 4 hours.

Note: sponging the body with tepid water is the safest way of cooling a feverish child.

Relieving a blocked and runny nose

When you have a cold, the lining of the nose becomes inflamed; resulting in increased production of mucus, and it may also become swollen.  This produces a runny nose followed by a blocked nose (congestion).  Drugs that reduce the swelling of the mucous membrane and suppress mucus production are called decongestants.  When taken by mouth in appropriate dosage these drugs act on nerves that supply the heart and blood vessels.  They constrict small arteries and reduce blood flow to many tissues in the body, including the nose where they shrink its lining and dry it up.  They may also increase the heart rate and send up the blood pressure.  They produce ‘adrenaline-like affects’ on the body.  They are related to the amphetamines (‘speed’) and are usually referred to as sympathomimetic drugs because they mimic stimulation of the sympathetic nervous system which uses noradrenaline as a nerve messenger.

Decongestant drugs by mouth affect the whole body and can be harmful in some people

Drugs that produce adrenaline-like affects on the body (sympathomimetic drugs) taken by mouth to relieve congestion of the nose include phenylephrine, phenylpropanolamine, and pseudoephedrine.  In addition to relieving congestion of the nose they may also produce general effects throughout the body which include an increase in the pulse rate and a rise in the blood pressure.  In high doses they may cause restlessness, anxiety, insomnia, trembling, rapid beating of the heart, disorders of the heart rhythm, dry mouth and cold hands and feet.  They may be harmful to people who have raised blood pressure or heart disease.  They may also be harmful to anyone with diabetes, because they send the blood sugar level up.  In someone with an overactive thyroid gland (thyrotoxicosis) they may trigger an irregular heart beat.  In somebody with coronary heart disease, the rise in pulse rate and blood pressure may trigger an attack of angina.

The message is clear – decongestant drugs by mouth may be harmful to some people because they constrict small arteries throughout the whole body as well as those in the nose.

WARNING: dangerous levels of phenylephrine, phenylpropanolamine and pseudoephedrine may occur in the body if you take a decongestant that contains one or more of these drugs by mouth and also use a decongestant nasal spray or nasal drops that also contain one or more of these drugs.  They may be particularly dangerous in patients taking an MAOI anti-depressant drug or within two weeks of stopping such a drug.

Decongestant drugs applied to the nose may also cause problems

Decongestant preparations that contain sympathomimetic drugs are available to be applied directly up the nose in the form of nose sprays and drops.  When applied in this way they cause the blood vessels to constrict and the lining of the nose to shrink.  This dries up the nose if it is running and unblocks it if it is blocked.  However, if used too frequently these nasal sprays and drops may cause a rebound swelling of the lining of the nose.  In other words when their effects have worn off, the congestion may become worse than it was before it was treated.  This may lead you to use the decongestant nose spray or drops again, which will cause a further rebound effect.  As a consequence, regular use may cause a chronic blocked nose which may be associated with overgrowth of the lining of the nose.

The commonly used sympathomimetic drugs in decongestant preparations to be applied up the nose are ephedrine, naphazoline, oxymetazoline, phenylephrine, phenylpropanolamine, pseudoephedrine and xylometazoline. They provide relief from a blocked nose for about 2-6 hours but remember that these drugs may be absorbed into the bloodstream, and produce harmful effects in some people.

Nasal decongestants may cause irritation and dryness of the nose, throat and mouth.  If over-used they may produce general harmful effects. Naphazoline and xylometazoline may, if over-used, be absorbed sufficiently into the bloodstream to depress the brain, causing coma and a marked reduction in body temperature, especially in infants.

WARNING:  use nasal decongestant sprays or drops to relieve a runny or blocked nose only when it is really necessary; for example, if you have to go to a meeting and cannot get out of it.  If you do have to use one, use it only two or three times daily for no more than a few days.  Remember, steam inhalations may provide transient relief and salt solution nose drops may also produce relief.

Cold remedies containing antihistamine drugs

Antihistamines used in cold (and cough) remedies include brompheniramine, chlorpheniramine, diphenhydramine, doxylamine, pheniramine and promethazine.

Antihistamines are used to treat allergies such as hayfever because they block the effects of histamine which is released from injured cells following the breathing in of a foreign protein, for example pollen.  The release of histamine produces ‘inflammation’ of the lining of the nose and throat, and causes symptoms like that of a bad cold.

In treating a common cold, the use of antihistamine drugs might be a good idea if the symptoms were actually caused by an allergic reaction and the release of histamine; but inflammation of a cold is caused by a virus infection and there is no evidence that antihistamine drugs are of benefit in relieving this type of inflammation.  However, in addition to their antihistamine effects, they affect the brain, producing drowsiness which may dampen down the cough control centre of the brain.  They may also produce slight drying up of the linings of the nose and air passages.  It is these usually unwanted harmful effects of antihistamines that are exploited when they are included in cold remedies.

The drying effect on the nose and air passages produced by antihistamines is a result of weak anticholinergic effects which these drugs produce.  This drying effect is usually slight, but even so it may interfere with the natural protection which the mucus covering of the air passages provides and may possibly do more harm than good. Also, the drowsiness caused by antihistamine drugs may be dangerous because it may affect your ability to drive and operate moving machinery. Furthermore, antihistamines may be particularly dangerous when taken with alcohol because they increase it effects.  They also increase the effects of sleeping drugs, tranquillizers and narcotic pain relievers.

Cold remedies that contain antihistamines known to produce marked drowsiness are usually recommended to be taken at bedtime; nevertheless, they may still produce hangover effects the next day in some people.

WARNING: In the treatment of common cold symptoms there is no convincing evidence from adequate and well controlled studies that the benefits of taking a cold remedy containing an antihistamine outweigh the risks.

Avoid cold remedies that contain anticholinergic drugs (e.g. atropine, belladonna, isopropamide)

Part of our nervous system is self-governing (autonomous). We have no voluntary control over it; for example, it controls our heart rate which increases automatically when we exercise and slows down when we rest.  The self-governing nervous system has two parts, which work against each other to produce a balance. One part is called the sympathetic system and stimulation of this produces many adrenaline-like effects such as increasing the heart rate. The other system works alongside the sympathetic and is called the parasympathetic system.  Stimulation of this system produces opposite effects to adrenaline.  It makes you sweat, produce more saliva and tears, tightens up your bronchial tubes, slows your heart rate, increases the movements of your gut, contracts your bladder (to make you pass urine) and constricts your pupils.  Stimulation also excites the brain.

These effects are produced by the release of a chemical messenger at nerve endings.  This messenger is called acetylcholine and the effects produced are called cholinergic effects (acetylcholine effects).  There are drugs that can produce these effects and they are called cholinergic drugs.  There is also a group of drugs that blocks these effects; they are called anticholinergic drugs.  Belladonna is an example of such a drug; it is found in the poisonous plant deadly nightshade.  These chemicals (of which atropine is the best example) can affect all organs and tissues supplied by the parasympathetic nervous system.  The ones included in some cold remedies include belladonna and isopropamide.

In the treatment of cold symptoms, anticholinergic drugs dry up the lining of the nose and air passages and act as decongestants.  This may interfere with the natural protection against infection which the mucus on these linings offers.  What is more, if given by mouth in effective doses, they produce more harmful effects than benefits; for example, blurred vision, dry mouth, constipation, difficulty in passing urine and confusion. They should not be used.  They are present in some herbal remedies usually in doses so low as to produce no effect. 

WARNING: Cold mixtures that contain an anticholinergic drug and an antihistamine drug expose the user to both the drowsiness produced by the antihistamine and the drying up of the nose and air passages produced by both drugs.  Such mixtures are not recommended.

Vapour rubs and inhalants used to treat colds

Steam inhalations may help to provide transient relief from a blocked nose and may soothe an irritating cough.  This treatment is safe and cheap but it obviously has no ‘magic’ in it; therefore it helps some individuals to add a substance whose vapour at least smells as if it might do some good.  These are usually aromatic essential oils such as eucalyptus oil, peppermint oil or pine oil, or aromatic substances such as camphor or menthol.  These aromatic substances are also included in vapour rubs and in preparations to be applied to handkerchiefs and clothing.  Because it is not always convenient to use steam inhalations, these preparations offer an alternative way of breathing in the vapours for those individuals who believe in them.

Harmful effects of essential oil vapours

Essential oils (e.g. peppermint, pine, eucalyptus) may irritate the skin and produce dermatitis.  Highly concentrated vapours of essential oil can kill mice and may produce sleepiness, coughs, headaches and liver and kidney damage in workers exposed to such vapours.  Highly concentrated vapours or the prolonged use of such vapours should therefore be avoided, especially in babies and infants.

Dangers of camphor

There have been reports of instant collapse of infants who have had a local application of camphor up their nostrils. Camphorated oil is toxic if swallowed accidentally and should not be used.

Dangers of menthol

Menthol can cause allergic reactions in some patients, producing nettle rash (uticaria), flushing and headache.  It may also cause dermatitis when applied to the skin.  There are reports of immediate collapse following the application of menthol to the nose of infants.  Also, menthol nose drops may cause spasm of the throat and make it difficult for young children to breath.

Does inhaling vapours help?

There is no doubt that some people find the smell of menthol and eucalyptus (and other essential oils) attractive and that they believe that they provide some relief from cold symptoms.  Certainly, the use of such vapours is an essential part of our folk medicine and they are very symbolic of caring and being cared for.  It would be difficult to design a study to determine whether their principal effects are in the mind or whether they produce direct beneficial effects on the air passages.  However, there is no convincing evidence from adequate and well controlled studies that they work, nor is there any convincing evidence that they do not work; and of course the same observation can be made about steam inhalations.  Nevertheless, inhaled vapours from applications applied to a handkerchief, applied to clothing or a pillow, rubbed into the chest or inhaled from an inhaler appear to provide transient relief of symptoms in some people, and if used only occasionally appear to be harmless.  However, they may be harmful if overused.  They should be used with utmost caution in babies under one month of age because strong applications may affect their breathing.

Vitamin C in the treatment of colds

The usefulness of high doses of vitamin C in the treatment of colds is a subject of controversy.  Those in favour of its use produce evidence that when you have a cold your body’s level of vitamin C is reduced and that you need to take additional vitamin C.  Some researchers have shown that vitamin C kills viruses and bacteria; others have shown that it has anti-inflammatory and antihistamine properties and that it is involved in the body’s immune system (defence against infections) and also involved in the repair when cells have been damaged by infection.  However, none of these observations has been definitely proved to be relevant to the treatment of colds, so there is still much controversy about whether or not vitamin C is beneficial.  Evidence that vitamin C and aspirin taken together is beneficial in colds is also contradictory.