Asthma is inflammation of the tubes of the lungs which causes them to be obstructed, and therefore air passes though them less easily.

The main symptoms are:

• Difficulty breathing or "shortness of breath", associated with a "tight" feeling. This may be associated with exercise, come on at night, or on exposure to various external stimuli.
• Audible wheeze is often present.
• Cough may be the main symptom in some children.

The cells in the lungs react to various irritants such as:

• Substances to which the individual is allergic (allergens) eg house dust mite, cat/dog fur, horses, pollen.
• Chemical irritants, eg cigarette/tobacco smoke, pollutants from factories and car exhausts, household cleaners and sprays, perfumes, etc.
• Low temperatures.
• Exercise.

This causes the tubes in the lungs to narrow which results in difficulty breathing.

Asthma frequently runs in families and is closely associated with hayfever and eczema. Sometimes other members of the family will have asthma, hayfever, or eczema, or combinations of these. It is essentially caused by an allergic type of reaction of the immune system. Sometimes the irritants which set off the reaction are not strictly allergens but chemical irritants eg smoke, some fumes.

In families with a strong history of this sort of condition, the genes which cause asthma are probably in place from birth, but the condition is activated by outside factors. These factors may include excessive exposure to house dust mites or smoke in the first few months of life, illness eg a severe infection, or exposure to irritant chemicals. There are various theories about why asthma is becoming more common, but some of these require more work to confirm or refute them.

Your doctor will want to demonstrate that your air flow is significantly limited at times and that this is reversible. He is likely to do this by asking you to use a peak flow meter which measures the fastest rate at which air comes out of your lungs when you blow into it as hard as you can. You will probably be tested in the surgery and then be given a prescription to get a meter of your own and asked to record regular readings.

You usually record these in a simple graphical form and take the best of three readings, twice a day. Your doctor may also give you an inhaler to try, which eases airway obstruction, asking you to record readings before and twenty to thirty minutes after using the inhaler.

Sometimes your doctor may wish to give a course of steroid tablets to assess the impact on your peak flow readings.

With all or some of these, your doctor should be able to find out whether or not you have asthma. In children who are too young to cooperate with peak flow readings the diagnosis can be more difficult and is often built up by the pattern over time and response to various medications.

As with most conditions you can treat Asthma with drugs from your doctor and by trying to prevent the symptoms of Asthma. For example avoiding dust and other irritants, which trigger Asthma, is an example of treating your Asthma by preventing it occurring in the first place.

There are two main types of drugs used for treating Asthma, and these are most commonly taken using an aerosol inhaler.

There are preventers that are taken every day, even if you feel well. They reduce the sensitivity of the cells in the lungs to house dust mites and other allergens. Some of these do not contain steroids eg sodium cromoglycate, and others which tend to be more effective, especially in moderate to severe asthma, contain steroids eg beclometasone, budesonide, and fluticasone. The steroid inhalers are usually a shade of brown or maroon, or sometimes peach coloured.

In the usual doses prescribed the total steroid dose to the body from these inhalers is not enough to cause significant adverse effects. It is wise, however, to rinse the mouth and throat by gargling with water after use of inhaled steroids. Any steroid that is left on the mouth and throat will not do any good to your asthma and may predispose you to infections in the throat and a hoarse voice. Alternatively, with young children encourage them to brush their teeth after using their preventer inhaler. (This should also please the dentist!)

This is salbutamol, one of the relievers available.

There are also relievers that are taken when you feel tight. If you have to take one more than once or twice a day, you should consult your doctor, because your doctor is likely to adjust the dose of preventer you are on. The relievers include salbutamol and terbutaline, and the inhalers are usually a shade of blue.

There are other inhalers which contain medication which works by a different mechanism and also cause opening of the tubes as well as reducing secretions, and others which are long acting forms of the tube opening (bronchodilator) medications. These may be added to your treatment if your doctor thinks it necessary.

One of the major problems with inhaled treatment is getting it to the right place in the lungs in adequate concentrations to have the desired effect. Although some people can use an inhaler well other people find the coordination of squeezing the device and inhaling the measured burst of medication very difficult to master.

There have thus been many attempts at alternative delivery systems:

• A "spacer" device between the aerosol and the patient. This may be a large volume spacer, which is usually about the shape and size of a one litre lemonade bottle, or a small volume spacer, which is a smaller circular tube. This results in much better distribution of the inhaled substance in the lungs, by allowing the medication to "hang" in the spacer until the patient breathes in. As well as improving delivery, this also reduces side effects in the mouth and throat which sometimes happen as a result of the pressurised medication hitting the throat at 80mph.

• Aerosols which automatically trigger when you breath in.

• Powder forms of the medication which are sucked into your lungs when you breath in, avoiding the need for an aerosol gas.

• Because of international constraints on the use of CFCs in aerosols, the propellant used in these inhalers has now been changed to exclude CFCs. These have slightly different properties and more of the active ingredient gets into the lungs. Especially as far as the steroid preventer inhalers are concerned, this means that your new inhaler may be more effective for the same dose of active medication. This does vary between manufacturers, so your doctor may well specify the brand of the inhaler, in order to ensure that you always receive the same product, but may also reduce your dose.

There are also tablets which open the tubes in the lungs and some of these also have anti-inflammatory effects. These may be used in some circumstances.

A newer form of preventative medication, leukotriene receptor antagonists, are now also used. It is taken in tablet form and works more specifically on the allergy/immune system. This group are thought to be "cleaner" drugs than the steroids, which are currently the mainstay of treatment, as they are more specific to the task involved. They are, however, at present used along side inhaled steroids and are aimed at mild to moderate asthma. So far they have proved to be very effective.

If possible avoid known triggers of Asthma, that is irritants known to make your breathing worse. If you smoke, stop.

Sometimes complete avoidance of trigger factors is impossible, as in the case of house dust mites, but you can take the following measures to lessen the house dust mite population:

• Cover all beds with a protective covering that does not allow the house dust mites to come through. It is also more hygienic because it can be easily wiped clean.

• Vacuum regularly with a vacuum cleaner with an efficient micro filter. If possible do this daily, including the mattress (if it doesn't have a protective covering) which is where the house dust mites breed. It is better if the person who suffers from asthma does not have to do this, as even with a high efficiency filter the actual process of vacuuming stirs up dust in the room air.

Patients themselves develop a very good idea of the severity of their asthma on a day to day basis, but it helps both them and the doctor to have an objective measure of the condition. Listening to the lungs is not very helpful, but peak expiratory flow meters (peak flow meters) give a very accurate idea of how tight the airways are.

These measure the fastest rate at which air comes out of your mouth when you blow as fast as you can. The measurement relies on maximum effort, but assuming that this is achieved, the muscle power of the muscles involved in blowing will not vary from day to day, and so changes in the reading are a result of change in the diameter of the airways. (A small change in diameter causes a fairly large change in air flow and thus the reading is very sensitive.)

• Asthma UK
• Canadian Lung Association
• Asthma Society of Canada

Books

The complete guide to asthma, by Dr Jonathan Brostoff

From a leading London allergy expert, this guide shows the reader how they can beat the illness. It includes alternative medicine and breathing exercises.
(Buy online from Amazon.com: USA, UK, Canada.)

BMA family doctor series: Asthma, by Professor Jon Ayres

An up to date guide for patients on asthma, written by one of Britain's leading experts.
(Buy online from Amazon.com: USA, UK, Canada.)

Beat your allergies (52 Brilliant ideas series), by Dr Rob Hicks

An excellent book, written by a British General Practitioner, which is easy to read, well laid out, and full of helpful ideas.
(Buy online from Amazon.com: USA, UK, Canada.)

Family guide to asthma and allergies, by American Lung Association Asthma Advisory Group

An informative guide to how to live with your asthma.
(Buy online from Amazon.com: USA, UK, Canada.)

Living with asthma, by Dr Robert Youngson

A self help book describing the condition, treatments, and what to do in an emergency.
(Buy online from Amazon.com: USA, UK, Canada.)