Asthma is a common 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.

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 (see below), your airways become narrow, the muscles around them tighten and there is an increase in the production of sticky mucus (phlegm). This leads to symptoms including:

• difficulty breathing
• wheezing and coughing
• a tight chest

Read more about the symptoms of asthma.

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.

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

What causes asthma?

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

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.

Read more about the causes of asthma.

Asthma can also be made worse by certain activities, such as work. For example, some nurses develop asthma symptoms after exposure to latex. This is often referred to as work-related asthma or occupational asthma.  

Treating asthma

While there is no cure for asthma, there are a number of treatments that can help effectively control the condition. Treatment is based on two important goals:

• relieving symptoms 
• preventing future symptoms and attacks from developing

Treatment and prevention involves a combination of medicines, lifestyle advice, and identifying and then avoiding potential asthma triggers.

Read more about living with asthma.

Who is affected?

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.