What is asthma?

Asthma is a common, long-term disease. It affects about five million people in the UK. This information is for adults and children over 12 years old.

People with asthma have very sensitive airways that become inflamed and tighten when they breathe in anything that irritates them. This can cause chest tightness and wheezing and make it harder to breathe.

Most people with asthma who receive the right treatment – and take it correctly – can control their symptoms and lead normal lives.

What happens in asthma?

Your airways carry air in and out of your lungs. If you have asthma, they are very sensitive. Certain things trigger the muscles around your airways to tighten, making your airways narrower. The airway lining also becomes inflamed causing a build-up of sputum. This makes your airways even narrower. With narrow airways, it’s harder to get air in and out of your lungs.

normal airways diagram
airways with asthma diagram

Next: Causes of asthma >

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Last medically reviewed: April 2017. Due for review: April 2020

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.