What is asthma?

Asthma is a condition that affects the airways – the small tubes that carry air in and out of the lungs.

When a person with asthma comes into contact with something that irritates their airways (an asthma trigger), the muscles around the walls of the airways tighten so that the airways become narrower and the lining of the airways becomes inflamed and starts to swell. Sometimes sticky mucus or phlegm builds up which can further narrow the airways. The illustration on the right shows a cross section of the airways, with and without inflammation.

All these reactions cause the airways to become narrower and irritated - making it difficult to breath and leading to symptoms of asthma.

• 5.4m people in the UK are currently receiving treatment for asthma.
• 1.1m children in the UK are currently receiving treatment for asthma.
• There is a person with asthma in one in five households in the UK.

Resources for teachers

• Myth busters (232 kb)
• More about asthma (423 kb)

Resources in Welsh

• Herio'r myth (1346 kb)
• Mwy am asthma (2696 kb)