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Asthma is a common condition that affects the airways. The typical symptoms are wheeze, cough, chest tightness, and shortness of breath. Symptoms can range from mild to severe. Treatment usually works well to ease and prevent symptoms.

Treatment is usually with inhalers. A typical person with asthma may take a preventer inhaler every day (to prevent symptoms developing) and use a reliever inhaler as and when needed (if symptoms flare up). This leaflet gives a general overview of asthma. There are other separate leaflets in this series.

Asthma is a condition that affects the smaller airways (bronchioles) of the lungs. From time to time the airways narrow (constrict) in people who have asthma. This causes the typical symptoms of asthma (see below). The extent of the narrowing, and how long each episode lasts, can vary greatly.

Asthma can start at any age but it most commonly starts in childhood. About 1.1 million of the 5.4 million people being treated for asthma in the UK are under 16 years old- which is roughly 20% of all people diagnosed with asthma. Asthma runs in some families but many people with asthma have no other family members affected.

The common asthma symptoms are cough and wheeze. You may also become breathless and develop a feeling of chest tightness. Asthma symptoms can range from mild to severe between different people and at different times in the same person. Each episode of asthma symptoms could last for an hour or so, or persist for days or weeks unless treated.

What are the typical symptoms if you have mild untreated asthma?

Mild asthma symptoms can occur from time to time. For example, you may develop a mild wheeze and a cough if you have a cold or a chest infection.You may also get mild symptoms during hay fever season, or when you exercise. Most of the time you could have no asthma symptoms at all. A child with mild asthma may have an irritating cough each night but is often fine during the day.

What are the typical symptoms if you have moderate untreated asthma?

You typically have episodes of wheezing and coughing from time to time. Sometimes you become breathless. You may have spells, sometimes long spells, without symptoms. However, you tend to be wheezy for some of the time on most days. Symptoms are often worse at night, or first thing in the morning. You may wake some nights coughing or with a tight chest. Young children may not have typical symptoms. It may be difficult to tell the difference between asthma and recurring chest infections in young children.

What are the typical symptoms of a severe asthma attack?

You become very wheezy, have a tight chest and have difficulty in breathing. You may find it difficult to talk because you are so breathless. Severe symptoms may develop from time to time if you normally have moderate symptoms. Occasionally, severe symptoms develop suddenly in some people who usually just have mild symptoms.

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The symptoms of asthma are caused by inflammation in the airways, which may be triggered by different things in different people. The inflammation causes the muscles around the airways to squeeze (contract). This causes narrowing of the airways. It is then more difficult for air to get in and out of the lungs. This leads to wheezing and breathlessness. The inflammation also causes the lining of the airways to make extra mucus which causes cough and further blockage to the airflow.

The following diagram below shows how an episode of asthma develops.

How asthma develops

Asthma diagram new

Asthma symptoms may flare up from time to time. There is often no obvious reason why asthma symptoms flare up. However, some people find that symptoms are triggered, or made worse, in certain situations. It may be possible to avoid certain triggers, which may help to reduce symptoms. Things that may trigger asthma symptoms include the following:

  • Infections - particularly colds, coughs and chest infections.
  • Pollens and moulds - asthma is often worse in the hay fever season.
  • Exercise - getting asthma symptoms when you exercise often means your asthma is undertreated. If it happens, it may mean you need to step up your usual preventer treatment (see below). Sport and exercise are good for you if you have asthma. If necessary, you can use an inhaler before exercise to prevent symptoms from developing.
  • Certain medicines - for example, about 1 in 50 people with asthma are allergic to aspirin, which can trigger symptoms. Other medicines that may cause asthma symptoms include:
    • Anti-inflammatory painkillers such as ibuprofen (for example, Nurofen®), diclofenac, etc.
    • Beta-blockers such as propranolol, atenolol, or timolol. This includes beta-blocker eye drops used to treat glaucoma.
  • Smoking and cigarette fumes - if you smoke and have asthma, you should make every effort to stop. See a pharmacist or practice nurse for help if you find it difficult. Passive smoking can make asthma worse too. Even where adults smoke away from children, smoke on clothes, hair, etc, may make asthma worse. All children deserve to live in a smoke-free home - in particular, children with asthma.
  • Other fumes and chemicals - for example, fumes from paints, solvents and pollution. The increase in air pollution may be a reason why asthma is becoming more common. Details about current levels of air pollution, are available from The Daily Air Quality Index, which can be found on the Department for Environment Food and Rural Affairs (DEFRA) website (see further reading for link).
  • Certain pillows and mattresses - feathers in pillows may trigger symptoms. It is thought that some people develop asthma symptoms from chemicals (isocyanates/methyl ethyl ketones, etc) that are emitted in very low quantities from memory foam pillows and mattress toppers.
  • Emotion - asthma is not due to 'nerves'; however, such things as stress, emotional upset, or laughing may trigger symptoms.
  • Allergies to animals - for example, pet cats and dogs, and horses. Some people notice that their symptoms become worse when close to certain animals.
  • House dust mite - this is a tiny creature which lives in mattresses and other fabrics around the home. If you are allergic to it, it may make symptoms worse. It is impossible to get rid of house dust mite completely. To greatly reduce their number takes a lot of time and effort and involves taking various measures. For example, using special mattress covers, removing carpets and removing or treating soft toys. However, if symptoms are difficult to control with treatment and you are confirmed to be allergic to house dust mite, it may be worth considering trying to reduce their number. See the separate leaflet called House Dust Mite and Pet Allergy for more details.
  • Some foods - this is uncommon. Food is not thought to be a trigger in most cases.

Some people only develop asthma symptoms when exposed to a certain trigger - for example, exercise-induced asthma. As mentioned above, exercise can make symptoms worse for many people with asthma. However, there are some people who only develop symptoms when they exercise; the rest of the time they are fine. Another example is that some people only develop symptoms when exposed to specific chemicals.

In the past, many cases of asthma were diagnosed on the basis of typical symptoms. However, these days guidelines recommend that doctors perform tests to confirm the diagnosis.


Spirometry is a test which measures how much air you can blow out into a machine called a spirometer. Two results are important:

  • The amount of air you can blow out in one second - called forced expiratory volume in one second (FEV1).
  • The total amount you can blow out in one breath - called forced vital capacity (FVC).

Your age, height and sex affect your lung volume. So, your results are compared with a graph showing the average predicted for your age, height and sex.

A value is calculated from the amount of air that you can blow out in one second divided by the total amount of air that you blow out in one breath (called FEV1:FVC ratio). A low value indicates that you have narrowed airways which are typical in asthma (but a low value can occur in other conditions too). Therefore, spirometry may be repeated after treatment with a reliever inhaler. An improvement in the value after treatment to open up the airways, is typical of asthma.

Note: spirometry may be normal in people with asthma who do not have any symptoms when the test is done. Remember, the symptoms of asthma typically come and go. Therefore, a normal result does not rule out asthma. However, if your symptoms suggest that you have asthma, ideally the test should be repeated when your symptoms are present. See the separate leaflet called Spirometry for more details.

Assessment with a peak flow meter

This is an alternative test. A peak flow meter is a small device that you blow into. A doctor or nurse will show you how. It measures the speed of air that you can blow out of your lungs. No matter how strong you are, if your airways are narrowed, your peak flow reading will be lower than expected for your age, height and sex. If you have untreated asthma then you will normally have low and variable peak flow readings. Also, peak flow readings in the morning are usually lower than in the evening if you have asthma.

You may be asked to keep a diary over two weeks of peak flow readings. Typically, a person with asthma will usually have low and variable peak flow readings over several days. Peak flow readings improve when the narrowed airways are opened up with treatment. Regular peak flow readings can be used to help assess how well the treatment is working. See the separate leaflet called Peak Flow Meter for Asthma and our editorial article called Peak flow diary for more details.

FeNO test

The National Institute for Health and Care Excellence (NICE) issued guidance in 2017 that most patients suspected of having asthma should have a fractional exhaled nitrous oxide (FeNO) test. A FeNO test measures the levels of nitric oxide in the breath. Increased levels are thought to be related to lung inflammation and asthma. Your GP may be able to provide this test, or you may be referred to a local clinic.

Other tests

If the diagnosis remains in doubt then a specialist may perform further, more complex tests. However, these are not needed in most cases.

Although not recommended for diagnosis, allergy tests may be used to identify any asthma triggers after a diagnosis of asthma has been made. See also the separate leaflet called Allergies.

Diagnosing asthma in children under 5 years old

Children under 5 often can't do the tests above accurately. So guidelines recommend that if your doctor suspects your under 5-year-old has asthma, they offer treatment based on their symptoms. However, once they reach the age of 5, they should have one or more of the tests below if they still have symptoms.

Diagnosing asthma in 5- to 16-year-olds

The European Respiratory Society (ERS) has suggested the main tests that should be used to diagnose asthma in young people. These include:

  • Spirometry.
  • FeNO (see above).
  • Using a 'reliever' inhaler to compare peak flow within a few minutes compared to before using it.
  • Some other specialist tests if the tests above don't give a diagnosis either way.

It does not recommend the following for diagnosis in 5- to 16-year-olds:

  • Making a diagnosis based on symptoms alone, without doing tests.
  • Relying on a single abnormal test.
  • A peak flow diary, looking at how peak flow varies.
  • Skin prick tests.
  • Using a preventer inhaler alone to see if symptoms improve.

For most people with asthma, the symptoms can be prevented most of the time with treatment. You are then able to get on with a normal life at school, work, sport, etc.


Most people with asthma are treated with inhalers. Inhalers deliver a small dose of medicine directly to the airways. The dose is enough to treat the airways. However, the amount of medicine that gets into the rest of your body is small so side-effects are unlikely, or minor. There are various inhaler devices made by different companies. Different ones suit different people. A doctor or nurse will advise on the different types. See the separate leaflet called Asthma Inhalers for more details.

Medicines delivered by inhalers can be grouped into relievers, preventers and long-acting bronchodilators (medicines that keep the airway open for a longer time):

  • A reliever inhaler is taken as needed to ease symptoms. The medicine in a reliever inhaler relaxes the muscle in the airways. This makes the airways open wider and symptoms usually quickly ease. These medicines are also called bronchodilators, as they widen (dilate) the bronchi and airways (bronchioles). There are several different reliever medicines - for example, salbutamol (Ventolin®)and terbutaline. These come in various brands made by different companies. If you only have symptoms every now and then, the occasional use of a reliever inhaler may be all that you need. However, if you need a reliever inhaler three times a week or more to ease symptoms, a preventer inhaler is usually advised.
  • A preventer inhaler is taken every day to prevent symptoms from developing. The medicine commonly used in preventer inhalers is a steroid. There are various brands. Steroids work by reducing the inflammation in the airways. When the inflammation has gone, the airways are much less likely to become narrow and cause symptoms. It takes 7-14 days for the steroid in a preventer inhaler to build up its effect. Therefore, it will not give any immediate relief of symptoms. However, after a week or so of treatment, the symptoms have often gone, or are much reduced. It can take up to six weeks for maximum benefit. You should then continue with the preventer inhaler every day even when your symptoms have gone - this is to prevent symptoms from coming back. You should then not need to use a reliever inhaler very often (if at all).
  • Bone strength (density) may be reduced following long-term use of high doses of inhaled steroids. Therefore people who regularly use steroid inhalers for asthma need to make sure they have a good supply of calcium in their diet. Milk and dairy aregood sources of calcium. Other good dietary sources of calcium include bread, some vegetables (curly kale, okra, spinach and watercress) and some fruits (for example, dried apricots). See the separate leaflet called Preventing Steroid-induced Osteoporosis for more details.
  • A long-acting bronchodilator may be advised in addition to a preventer inhaler. Long-acting bronchodilators relieve symptoms as they widen the lung airways (bronchi) but work for longer than reliever inhalers. The medicines in these inhalers work for up to 12 hours after each dose has been taken. They include salmeterol and formoterol. (Some brands of inhaler contain a steroid plus a long-acting bronchodilator for convenience.) A long-acting bronchodilator may be needed if symptoms are not fully controlled by the preventer inhaler alone.

Spacer devices are used with some types of inhaler. They are commonly used by children; however, many adults also use them. A spacer is like a small plastic chamber that attaches to the inhaler. It holds the medicine like a reservoir when the inhaler is pressed. A valve at the mouth end makes sure that the medicine is kept within the spacer until you breathe it in. When you breathe out, the valve closes. You don't need to have good co-ordination to inhale the medicine if you use a spacer device. A face mask can be fitted on to some types of spacers instead of a mouthpiece. This is sometimes done for babies and young children who can then use the inhaler simply by breathing in and out normally through the mask.

Tablets to open up the airways

Most people do not need tablets, as inhalers usually work well. However, in some cases a tablet (or medicine in liquid form for children) is prescribed in addition to inhalers if symptoms are not fully eased by inhalers alone. Various tablets may be used which aim to open up the airways. Some young children use liquid medication instead of inhalers.

Leukotriene receptor antagonists (LTRAs)

Chemicals called leukotrienes are produced in some people who have asthma which is triggered by an allergic reaction (eg, pollen) or sometimes exercise. LTRAs such as montelukast act by blocking the action of these chemicals. Montelukast comes in the form of tablets or granules. In people whose asthma is not well controlled by a reliever inhaler and a preventer inhaler, NICE recommends trying an LTRA before adding a long-acting bronchodilator inhaler.

Steroid tablets

A short course of steroid tablets (such as prednisolone) is sometimes needed to ease a severe or prolonged attack of asthma. Steroid tablets are good at reducing the inflammation in the airways. For example, a severe attack may occur if you have a cold or a chest infection.

Some people worry about taking steroid tablets. However, a short course of steroid tablets (for a week) usually works very well and is unlikely to cause side-effects. Most of the side-effects caused by steroid tablets occur if you take them for a long time (more than several months), or if you take a lot of short courses of high-dose steroids over a short period of time.

Biologic therapies for keeping airways open

Monoclonal antibodies are biologic treatments used for treating many diseases. They work by targeting specific cells andd proteins to make the disease better. In asthma, they work by interfering with the immune system to reduce inflammation in the airways. These are medicines that are only used in a small number of people who have severe persistent allergic asthma that have not been controlled by other treatments. So, it is not a common treatment. They are most commonly given by injection. These treatments can only be started by a specialist.

Currently there are five treatments used in the NHS and recommended by NICE:

  • Mepolizumab (Nucala).
  • Reslizumab (Cinqaero®) - this one is given through your vein as a drip.
  • Benralizumab (Fasenra®).
  • Omalizumab (Xolair®).
  • Dupilumab (Dupixent®).

Each medication has its own rules on when they can be started by a specialist. If you need them, your doctor will go into much more detail about that specific one.

Editor's note

Dr Krishna Vakharia, 21st April 2023

NICE has recommended another biologic therapy called tezepelumab which works similarly to the ones above.

It can be used in those over the age of 12 and only if they meet certain criteria. It is mainly used in those with severe asthma when treatment with high-dose inhaled corticosteroids and another maintenance treatment is not working well enough to control symptoms. If you meet the criteria, your specialist will discuss this option with you. See Further Reading below.

Everyone is different. The correct dose of a preventer inhaler is the lowest dose that prevents symptoms. A doctor may prescribe a high dose of a preventer inhaler at first, to 'get on top of symptoms' quickly. When symptoms have gone, the dose may then be reduced by a little every few weeks. The aim is to find the lowest regular dose that keeps symptoms away.

Some people with asthma put up with symptoms. They may think that it is normal still to have some symptoms even when they are on treatment. A common example is a night-time cough which can cause disturbed sleep. But, if this occurs and your symptoms are not fully controlled, tell your doctor or nurse. Symptoms can often be prevented - for example, by adjusting the dose of your preventer inhaler, or by adding in a long-acting bronchodilator.

A common treatment plan for a typical person with moderate asthma is:

  • A preventer inhaler (usually a steroid inhaler), taken each morning and at bedtime. This usually prevents symptoms throughout the day and night.
  • A reliever inhaler may be needed now and then if breakthrough symptoms occur. For example, if symptoms flare up when you have a cough or cold.
  • If exercise or sport causes symptoms then a dose of a reliever inhaler just before the exercise usually prevents symptoms.
  • The dose of the preventer inhaler may need to be increased for a while if you have a cough or cold, or during the hay fever season.
  • Some people may need to add in an LTRA and/or a long-acting bronchodilator if symptoms are not controlled with the above.

At first, adjusting doses of inhalers is usually done on the advice of a doctor or nurse. In time, you may agree an asthma action plan with your doctor or nurse.

What is an asthma action plan?

An asthma action plan is a plan agreed by you with your doctor or nurse. The plan enables you to make changes to the dose of your inhalers, depending on your symptoms and/or peak flow readings. The plan is tailored to you. It is written down, usually on a standard form, so you know what to do at any time.

Your plan should include:

  • What to do when you are unwell - for example, with a cold - and when to seek help.
  • What to do if your symptoms become worse with hayfever or exercise.
  • A discussion on ways to reduce your exposure to air pollution around you, both indoors and outdoors. If your asthma is triggered by household sprays, air fresheners or aerosols, you should try to avoid using them or use non-spray alternatives instead. Mould and house dust mites in the home can also make asthma worse. If you have problems with mould in your home, speak with your GP - they sometimes can help you request a housing assessment from the local authority.
  • What to do if you have a severe asthma attack.

Research studies suggest that people who complete personal asthma action plans find it easier to manage their asthma symptoms and that their plan helps them to go about their lives as normal. Asthma+Lung UK provides asthma action plans which you can download from

There is no once-and-for-all cure. However, about half of the children who develop asthma grow out of it by the time they are adults.

For many adults, asthma is variable with some good spells and some spells that are not so good. Some people are worse in the winter months and some are worse in the hay fever season. Although not curable, asthma is treatable. Stepping up the treatment for a while during bad spells will often control symptoms.

Don't underestimate asthma

Because modern management is so effective, many people with asthma are well controlled. However, this has led to the belief that asthma is a mild and even trivial condition.

The fact is that when asthma goes wrong, it can do so quickly. Deaths from asthma are rising. More than 1,400 people died from asthma in 2020, representing an increase of nearly 4% over the previous year..

There are several things you can do lower the risk of your asthma getting out of control:

  • Make sure you are accessing basic asthma care. This should involve at least an annual review from your GP or asthma nurse, including an inhaler technique check. You should be given a written asthma action plan.
  • Take your medication as prescribed.
  • If you develop symptoms which are not responding to your action plan, seek advice from a healthcare professional immediately.

"It's only asthma" is not a phrase that should pass anybody's lips.

  • It is vital that you learn how to use your inhalers correctly. In some people, symptoms persist simply because they do not use their inhaler properly and the medicine from the inhaler does not get into the airways properly. See your pharmacist or practice nurse if you are not sure if you are using your inhaler properly.
  • See a doctor or nurse if symptoms are not fully controlled, or if they are getting worse. For example, if:
    • A night-time cough or wheeze is troublesome.
    • Sport is being affected by symptoms.
    • Your peak flow readings are lower than normal.
    • You need a reliever inhaler more often than usual.
    An adjustment in inhaler timings or doses may control these symptoms.
  • See a doctor urgently if you develop severe symptoms that are not eased by a reliever inhaler. In particular, if you have difficulty talking due to shortness of breath. You may need emergency treatment with high-dose reliever medicine and other treatments, sometimes in hospital. A severe asthma attack can be life-threatening. In this case, call for an ambulance.
  • You should have an influenza immunisation every autumn (the flu jab) if you need continuous or repeated use of high-dose inhaled steroids and/or take steroid tablets and/or have had an episode of asthma which needed hospital admission.

Asthma Inhalers

Further reading and references