Asthma is a long-term condition that can cause a cough, wheezing and breathlessness. The severity of the symptoms varies from person to person. Asthma can be controlled well in most people most of the time.

In the UK, 5.4 million people are currently receiving treatment for asthma. That is 1 in every 12 adults and 1 in every 11 children. Asthma in adults is more common in women than men.

If you are diagnosed with asthma as a child, the symptoms may disappear during your teenage years. However, asthma can return in adulthood. If childhood symptoms of asthma are moderate to severe, it is more likely that the condition will persist or return later in life. However, asthma does not only start in young people and can develop at any age.

The cause of asthma is not fully understood, but it is known that asthma often runs in families. You are more likely to have asthma if one or both of your parents has the condition.

What is asthma?

Asthma is caused by inflammation of the airways. These are the small tubes, called bronchi, which carry air in and out of the lungs. If you have asthma, the bronchi will be inflamed and more sensitive than normal. When you come into contact with something that irritates your lungs, known as a trigger, your airways become narrow, the muscles around them tighten and there is an increase in the production of sticky mucus (phlegm). This makes it difficult to breathe and causes wheezing and coughing. It may also make your chest feel tight.

A severe onset of symptoms is known as an asthma attack or an 'acute asthma exacerbation'. Asthma attacks may require hospital treatment and can sometimes be life-threatening, although this is rare.

For some people with chronic (long-lasting) asthma, long-term inflammation of the airways may lead to more permanent narrowing.

Common triggers

A trigger is anything that irritates the airways and brings on the symptoms of asthma. These differ from person to person and people with asthma may have several triggers.

Common triggers include house dust mites, animal fur, pollen, tobacco smoke, exercise, cold air and chest infections.

Other types of asthma

There are other types of asthma that can be made worse by certain activities:

• Work-aggravated asthma is pre-existing asthma that is made worse by dust and fumes at work. 
• Occupational asthma is caused by exposure to specific substances at work. For example, some nurses develop occupational asthma after exposure to latex, and some workers in the food-processing industry develop occupational asthma as a response of exposure to flour.

Outlook

While there is no cure for asthma, symptoms can come and go throughout your life. A number of treatments can help control the condition very effectively. Treatment is based on two important goals:

• relief of symptoms 
• preventing future symptoms and attacks from developing

For more information, see Asthma - treatment.

Successful prevention can be achieved through a combination of medicines, lifestyle advice and identifying and then avoiding potential asthma triggers.