What is asthma, symptoms of asthma, Causes of asthma

Introduction

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

More about the symptoms of asthma

The symptoms of asthma can range from mild to severe. Most people will only experience occasional symptoms, although a few people will have problems most of the time.

The main symptoms of asthma are:

• wheezing (a whistling sound when you breathe)
• shortness of breath
• a tight chest – which may feel like a band is tightening around it 
• coughing

These symptoms are often worst at night and early in the morning, particularly if the condition is not well controlled. They may also develop or become worse in response to a certain trigger, such as exercise or exposure to an allergen. Read our page on the causes of asthma for more information about potential triggers.

Speak to your GP if you think you or your child may have asthma. You should also talk to your doctor or asthma nurse if you have been diagnosed with asthma and you are finding it difficult to control the symptoms.

Causes of asthma

It's not clear exactly what causes asthma, although it is likely to be a combination of factors.

Some of these may be genetic. However, a number of environmental factors are thought to play a role in the development of asthma – these include air pollution, chlorine in swimming pools and modern hygiene standards (known as the "hygiene hypothesis").

There is currently not enough evidence to be certain whether any of these can cause asthma, although a variety of environmental irritants such as dust, cold air and smoke may make it worse.

Who is at risk?

Although the cause of asthma is unknown, a number of things that can increase your chances of developing the condition have been identified. These include:

• having a family history of asthma or other related allergic conditions (known as atopic conditions) – such as eczema, food allergy or hay fever
• having another atopic condition yourself
• having bronchiolitis (a common childhood lung infection) as a child
• being exposed to tobacco smoke as a child – particularly if your mother also smoked during pregnancy 
• being born prematurely – especially if you needed a ventilator to support your breathing after birth

having a low birth weight as a result of restricted growth within the womb