Asthma is a condition that affects the smaller airways (bronchioles) of the lungs. In asthma, the airways narrow (constrict) causing the typical symptoms of cough and wheeze. The extent of the narrowing, and how long each episode lasts, can vary.

Asthma can start at any age but it most commonly starts in childhood. At least 1 in 10 children and 1 in 20 adults have asthma. Asthma runs in some families but many people with asthma have no other family members affected.

Asthma symptoms:

    • cough

    • wheeze

    • breathless

    • feeling of chest tightness

Symptoms can range from mild to severe between different people and at different times in the same person. Each episode of symptoms may last just an hour or so, or persist for days or weeks unless treated.

Young children may not have typical symptoms. It may be difficult to tell the difference between asthma and recurring chest infections in young children.

What causes asthma?

The symptoms of asthma are caused by inflammation in the airways. This may be triggered by various things. The inflammation causes the muscles around the airways to squeeze (contract) and as a result narrowing of the airways. This makes it more difficult for air to get in and out of the lungs and leads to wheezing and breathlessness. The inflammation also causes the lining of the airways to make extra mucus which causes cough and further obstruction to airflow.

The diagram below shows how an episode of asthma develops.

Triggers of Asthma

    • Infections - particularly colds, coughs and chest infections.

    • Pollens and moulds

    • Exercise - however, sport and exercise are good for you if you have asthma. If necessary, you can use an inhaler before exercise to prevent symptoms from developing. But, as a rule, exercise-induced asthma often represents undertreated asthma. If it occurs, it may indicate a need to step up your usual preventer treatment (see below).

    • Certain medicines - for example, about 1 in 50 people with asthma are allergic to aspirin, which can trigger symptoms. Other medicines that may cause asthma symptoms include:

      • Anti-inflammatory painkillers such as ibuprofen (for example, Nurofen®), diclofenac, etc.

      • Beta-blockers such as propranolol, atenolol, or timolol.

    • Smoking and cigarette fumes - if you smoke and have asthma, you should make every effort to stop. Passive smoking can make asthma worse too. Even where adults smoke away from the presence of children, smoke on clothes, hair, etc, may make asthma worse.

    • Other fumes and chemicals - for example, fumes from paints, solvents and pollution. The increase in air pollution may be a reason why asthma is becoming more common. In Sinagpore the Haze can be a common trigger.

    • Certain pillows and mattresses - feathers in pillows may trigger symptoms. It is thought that some people develop asthma symptoms from chemicals (isocyanates/methyl ethyl ketones, etc) that are emitted in very low quantities from memory foam pillows and mattress toppers.

    • Allergies to animals - for example, pet cats and dogs, and horses.

    • House dust mite - this is a tiny creature which lives in mattresses and other fabrics around the home. If you are allergic to it, it may make symptoms worse. It is impossible to get rid of house dust mite completely. To greatly reduce their number takes a lot of time and effort and involves taking various measures. For example, using special mattress covers, removing carpets and removing or treating soft toys.



Most people with asthma are treated with inhalers. Inhalers deliver a small dose of medicine directly to the airways. The dose is enough to treat the airways. However, the amount of medicine that gets into the rest of your body is small so side-effects are unlikely, or minor. There are various inhaler devices made by different companies. Different ones suit different people. A doctor or nurse will advise on the different types. See separate leaflet called Inhalers for Asthma (including Inhaled Steroids) for more details.

Medicines delivered by inhalers can be grouped into relievers, preventers and long-acting bronchodilators:

A reliever inhaler is taken as required to ease symptoms. The medicine in a reliever inhaler relaxes the muscle in the airways. This makes the airways open wider and symptoms usually quickly ease. These medicines are also called bronchodilators, as they widen (dilate) the bronchi and airways (bronchioles). There are several different reliever medicines - for example, salbutamol and terbutaline. These come in various brands made by different companies. If you only have symptoms every now and then, the occasional use of a reliever inhaler may be all that you need. However, if you need a reliever inhaler three times a week or more to ease symptoms, a preventer inhaler is usually advised.

A preventer inhaler is taken every day to prevent symptoms from developing. The medicine commonly used in preventer inhalers is a steroid. There are various brands. Steroids work by reducing the inflammation in the airways. When the inflammation has gone, the airways are much less likely to become narrow and cause symptoms. It takes 7-14 days for the steroid in a preventer inhaler to build up its effect. Therefore, it will not give any immediate relief of symptoms. However, after a week or so of treatment, the symptoms have often gone, or are much reduced. It can take up to six weeks for maximum benefit. You should then continue with the preventer inhaler every day even when your symptoms have gone - to prevent symptoms from coming back. You should then not need to use a reliever inhaler very often (if at all).

Bone strength (density) may be reduced following long-term use of high doses of inhaled steroids. Therefore people who regularly use steroid inhalers for asthma need to make sure they have a good supply of calcium in their diet. Milk is a good source of calcium but dairy products may need to be avoided for some people with asthma. Other good dietary sources of calcium include bread, some vegetables (curly kale, okra, spinach and watercress) and some fruits (for example, dried apricots). See separate leaflet called Preventing Steroid-induced Osteoporosis for more details.

A long-acting bronchodilator may be advised in addition to a preventer inhaler. Long-acting bronchodilators relieve symptoms as they widen the lung airways (bronchi) but work for longer than reliever inhalers. The medicines in these inhalers work for up to 12 hours after each dose has been taken. They include salmeterol and formoterol. (Some brands of inhaler contain a steroid plus a long-acting bronchodilator for convenience.) A long-acting bronchodilator may be needed if symptoms are not fully controlled by the preventer inhaler alone.

How to use your inhaler using a spacer

How to use your inhaler through your mouth

Using a turbohaler