Asthma
Clinical review by: Dr Edward Cetti, Consultant Respiratory Physician
Content editor review by Julia Ebbens, October 2026
Next review due October 2029
Key points
- Asthma causes swelling in your airways which can cause wheezing, coughing or breathing difficulties.
- Doctors can diagnose asthma by using breathing or inflammation tests.
- You can treat asthma with a personalised plan, including inhaled medications.
Asthma is a common, long-term condition that affects the airways in your lungs. It can affect people differently but can cause wheezing and make you cough. Your chest may feel tight and you may feel short of breath too. Asthma medicines and avoiding things that trigger symptoms will help to keep it under control.
What is asthma?
Asthma affects your airways (the tubes that carry air in and out of your lungs). Your airways become inflamed and sensitive to things that can cause allergies. Your airways narrow and your body produces more mucus, which can block your airways too. This makes it more difficult for air to flow in and out of your lungs, which makes it harder for you to breathe.
It's common to develop asthma as a child, but it can start at any age. Over five million people in the UK are being treated for asthma.
Sometimes children grow out of it, and their asthma symptoms reduce as they grow older until they no longer have them. But for some people, asthma symptoms can come back after years of being symptom-free, and for others, it can be lifelong.
Asthma symptoms can vary from mild to severe. When asthma is severe, and you have a flare-up of symptoms (an asthma attack), it can be serious and even life-threatening. Asthma attacks are less likely to happen if you manage your condition well and many asthma attacks can be prevented.
What causes asthma?
There isn’t a single cause of asthma. It happens because of a combination of your genetics and something in your environment. Sometimes we don’t know why it happens.
Some things make asthma more likely, which include if you:
- have family with asthma
- have other allergy-related conditions, such as eczema and hayfever
- have chest infections caused by a virus when you’re a child
- are exposed to cigarette smoke when you’re in the womb and as a baby
- come into contact with certain substances at work, such as flour, hairdressing and cleaning products, chemicals and sawdust
- are overweight
Many things can make your asthma symptoms flare up. These are called triggers and may include:
- a recent cold or sinusitis
- allergies to pollen, animals (commonly cats, dogs and horses), house dust mites, or certain foods
- air pollution, including cigarette smoke
- exercise, especially in cold or dry environments
- emotions, such as laughing, anger or stress (especially in children)
- changes in the weather, such as a change in air temperature
- certain medicines, such as aspirin and beta-blockers
What are the symptoms of asthma?
The main asthma symptoms are:
- coughing
- wheezing
- finding it difficult to breathe
- tightness in your chest
You may not have all these symptoms but you'll probably have at least a couple if you have asthma. If you have any of these symptoms, see your GP.
Your asthma symptoms may be worse at night, or early in the morning. Asthma symptoms usually come and go. You might notice that something specific started your symptoms, such as high pollen levels or being in contact with a cat.
Asthma attack
If your asthma symptoms flare up suddenly, it’s called an asthma attack. You’re having an asthma attack if:
- your symptoms are getting worse – you’re wheezing or coughing a lot and your chest feels tight
- you’re too out of breath to talk or walk
- your breathing is getting faster and it feels like you can't breathe in properly
- your (blue) reliever inhaler isn't helping, or isn't lasting more than four hours
If this is happening, get help straightaway. For more information, see our section on what to do if you have an asthma attack.
How is asthma diagnosed?
There's no single test to diagnose asthma. But there are tests that can give doctors a good idea of how likely you are to have it.
When you see a GP, they'll ask about your symptoms and examine you. Your GP will also ask about your medical history and whether anyone in your family has asthma, allergies or hayfever. If you think you know what triggered or started your symptoms, tell your GP.
Your GP may use a stethoscope to listen for wheezing sounds in your lungs.
If your GP thinks that you have an asthma diagnosis, they may ask you to have one or more of these tests.
- Spirometry. This measures how much air you can breathe out in one breath. It’s sometimes done before and after you take asthma medicines to see how well they work.
- Peak flow meter. For this test you blow a breath out into a machine as hard as you can. You may need to do the test several times a day over a few weeks and keep a diary of your readings.
- A FeNO (fractional exhaled nitric oxide) test measures the amount of a gas called nitric oxide in your breath.
Tests for asthma tend not to work well in children under five or for some older children. So your GP may treat the symptoms they see, rather than carry out these tests.
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What is the treatment of asthma
Asthma treatment involves taking medicines to control your symptoms and reduce the risk of you having an asthma attack. When you get an asthma diagnosis, your GP will prescribe medicines, and increase or reduce them until your symptoms are well controlled. The aim is for you to take the smallest amount you need to stay free of asthma symptoms. That means:
- having no asthma symptoms during the day
- not waking up due to asthma
- not having any asthma attacks
- having no limits to the activities you can do
You usually take asthma treatment medicines by breathing them in, often with an asthma inhaler. There are two basic types of inhaler medicines for asthma.
- Relievers. These are called beta-2-agonists and you use one to treat your symptoms as soon as they start. If you need to use your reliever inhaler three times a week or more, or your asthma is worse at night, talk to your GP. This suggests your asthma isn’t well controlled and you have a higher risk of an asthma attack. They might suggest you take a preventer medicine as well. Reliever inhalers are usually a blue colour.
- Preventers. These are inhalers or sometimes tablets. Preventer inhalers contain a small amount of steroid medicine, which can help to control inflammation in your airways and prevent your symptoms. Use it once or twice every day, even if you don’t have asthma symptoms. Preventer inhalers are often brown, but the colour can vary.
Your GP or nurse will give you a personalised asthma action plan. This has information about how and when you should use your asthma inhalers, as well as what to do if your asthma gets worse.
Inhalers, spacers and nebulisers
You take many asthma medicines by breathing them in, and there are different ways to do this.
- Inhalers are plastic devices with a mouthpiece, and a pressurised can that contains the medicine. You push down on the can and a measured amount comes out as a fine mist. Inhalers can be hard to use for some people. If you find it difficult, you can try a spacer with your inhaler, a dry powder inhaler or a breath-activated inhaler instead.
- Spacers are plastic cylinders that you attach to the end of your asthma inhaler. You use the inhaler as normal but breathe the medicine in from the spacer mouthpiece. You don't need to time your breathing with pushing the inhaler, which makes it easier.
- Nebulisers are machines that turn liquid asthma medicines into a fine mist that you breathe in through a mouthpiece or face mask. You may need to use a nebuliser if you’re having a severe asthma attack.
Whatever device you use to take your medicines, it’s important to use it properly. It can make a real difference to how well your asthma is controlled. If you don’t, you may get side-effects, such as a sore mouth. It can also mean the medicine doesn’t get right into your airways so won’t work as well as it should. If you’re unsure how to use your asthma inhaler correctly, ask your GP or asthma nurse for help.
Other medicines
If your asthma is not well controlled, your doctor or nurse may first check you are using your inhaler and medication correctly. If these don’t help your doctor may suggest you take a medicine called a leukotriene receptor antagonist to reduce inflammation, or a long-acting reliever to lower your risk of asthma attacks. You may need to try some of these medicines for a month or two to see how well they work. If your asthma is severe and not well controlled after trying them, your GP may refer you to a specialist.
What to do if you have an asthma attack
An asthma attack is a sudden flare-up of your symptoms. It can be frightening so it’s a good idea to have a plan and know what to do if it happens. Your personal asthma plan should have information about how to manage your asthma and what to do if you think you’re having an asthma attack.
If you’re having an asthma attack, you need to get help straightaway. Be as calm as you can and take the following steps.
- Sit up – don’t lie down.
- Take four puffs of your reliever inhaler immediately. If you have a spacer, use it. Children should have a puff every 30 to 60 seconds, taking up to 10 puffs.
- If your symptoms don’t get better, take two puffs of your inhaler every two minutes. You can take up to 10 puffs until your symptoms go away.
- If your symptoms don’t go away promptly, call 999.
If your symptoms get better and you don’t need to call an ambulance, still see your GP or asthma nurse within 48 hours. They may need to review your treatment.
How a reliever works to treat an asthma attack
Relieve an asthma attack | Watch in 2 minutes 2 seconds
This video shows how a reliever works to treat an asthma attack.
This animation will show what happens in the lungs during an asthma attack and how a reliever inhaler works to treat it.
Air (oxygen) is taken in through the mouth and nose.
It then passes through the trachea to the bronchi.
Asthma is a condition where the airways become irritated and inflamed.
The bronchi are large tubes which are found in the lungs.
Air flows through these tubes.
The bronchi branch and narrow into tubes called bronchioles.
The bronchioles continue to branch and end with tiny air sacs called alveoli.
In healthy lungs, oxygen is taken into the body through the bronchi and passes into the blood via the alveoli.
If you have an asthma attack you may start wheezing, your chest may feel tight and you may be breathless.
The muscles in the walls of the airways tighten and the inner surface swells, causing the airways to narrow.
An asthma attack can be triggered by exercise or an allergy for example, both of which can irritate the airways.
When the airways narrow it's harder to breathe.
Reliever inhalers are used to widen the airways so you can breathe more easily if you have an asthma attack.
The inhaler contains a gas which propels the medicine into the airways so that the muscle walls relax and the airways open up.
When the airways widen it's easier to breathe.
This is the end of the animation.
Management of asthma
Asthma is a long-term condition and it’s important to work with health professionals to keep your symptoms under control. This is called self-management. Your doctor or asthma nurse will give you information about asthma, how to manage it and your own action plan.
Your action plan could include:
- how to recognise if your asthma is getting worse
- changes to your medicines, and when you will make those changes
- how to monitor your asthma
If you use your action plan, your asthma is likely to be better controlled. You’re also less likely to need to go into hospital for treatment.
You’ll have a review of your asthma and medicines once a year, or more often if you’ve had an asthma attack or have severe asthma. During the review, your nurse or GP will check how you use your asthma inhaler.
As well as managing your asthma symptoms, there are things you can do to help improve your symptoms. These include:
- losing any excess weight
- stopping smoking if you smoke
- giving children all their routine vaccinations
- having a yearly flu vaccination
Breathing exercises may help to control your asthma symptoms too. Your GP may refer you to a physiotherapist, who can show you these exercises.
The symptoms of asthma are coughing, wheezing, difficulty breathing and tightness in your chest. Asthma symptoms usually come and go. They may be worse at night, or early in the morning. If your asthma symptoms flare up suddenly, it’s called an asthma attack.
See our Symptoms of asthma section for more information.
There isn’t a single cause of asthma. Asthma is caused by your genetics and sometimes, things in your environment. Some things can increase your risk of asthma, such as if you have eczema and hayfever. Many things can make your asthma symptoms flare up, such as allergies to pollen, animals, house dust mites or air pollution.
See our Causes of asthma section for more information.
The signs of an asthma attack are:
- your symptoms are getting worse – you’re wheezing or coughing a lot and your chest feels tight
- you’re too out of breath to talk or walk
- your breathing is getting faster and it feels like you can't breathe in properly
- your (blue) reliever inhaler isn't helping, or isn't lasting more than four hours
If this happens to you, get medical help straightaway.
See our What to do if you have an asthma attack section for more information.
Yes, there are different types of asthma. These include the following.
- Seasonal asthma, which only flares up at certain times of the year, such as during hayfever season, or when it’s cold.
- Occupational asthma, where your job causes asthma. For example, hairdressing products can cause it.
- Non-allergic asthma isn’t related to an allergy trigger like pollen or dust.
Asthma can also be divided into different severities and age groups of people who develop it too. Your asthma specialist may sometimes suggest a blood test, which can help identify some of the types of asthma and guide what your treatment options are.
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