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Asthma causes the airways of the lungs (the bronchi) to become inflamed and swollen.

The bronchi are small tubes that carry air in and out of your lungs. If you have asthma, the bronchi are more sensitive than normal and certain substances or triggers can irritate them.

Common triggers include house dust mites, animal fur, pollen, tobacco smoke, cold air and chest infections.

When the bronchi are irritated, they become narrow and the muscles around them tighten, which can increase the production of sticky mucus, or phlegm. This makes it difficult to breathe and causes wheezing and coughing, and it may make your chest feel tight.

The severity of the symptoms of asthma differs from person to person, from mild to severe. The narrowing of the airways is usually reversible – occurring naturally, or through the use of medicines. However, for some people with chronic (long-lasting) asthma, the inflammation may lead to an irreversible obstruction of the airways.

A severe onset of symptoms is known as an asthma attack, or 'acute asthma exacerbation'. Asthma attacks can be life-threatening and may require hospital treatment.

The cause of asthma is not fully understood, but it is thought to be a combination of genetic (inherited) and environmental factors. Asthma often runs in families, and you can inherit the susceptibility to asthma, which is then triggered by certain factors in the environment.

Factors include exposure to air pollutants, such as cigarette smoke, or certain substances that can cause allergic reactions (allergens), such as pollen or animal fur.

There is no cure for asthma, but there are a number of treatments that can normally manage the condition. Treatment is based on two important goals:

  • Relief of symptoms.
  • Preventing future symptoms from developing.

Successful prevention can be achieved through a combination of medicines, lifestyle advice and identifying and then avoiding potential asthma triggers.

There are also different types of pre-existing asthma that can be made worse by certain activities:

Work-aggravated asthma is a pre-existing asthma that is made worse by dust and fumes at work.

Occupational asthma is due to exposure to specific substances at work. Often these substances are specific to certain occupations. For example, some nurses develop occupational asthma as a response to prolonged exposure to latex, and some workers in the food-processing industry develop occupational asthma as a response to prolonged exposure to flour.

Exercise-induced asthma is a pre-existing asthma brought on by physical exercise. However, for most people it is an indication of poorly controlled asthma


There is no single known cause of asthma, but there are several factors that may contribute to the condition.

Contributory factors include a genetic predisposition (having something in your genes that makes it more likely that you will develop asthma), diet and the environment.

Known risk factors for the development of asthma include:

  • a family history of asthma, or other related allergic conditions (known as atopic conditions), such as eczema, hayfever or allergic conjunctivitis (inflammation of the eyes),
  • developing another atopic condition,
  • having bronchiolitis as a child (bronchiolitis is a lung infection common among children),
  • being exposed to tobacco smoke as a child, particularly if your mother smoked during pregnancy,
  • being born prematurely, and
  • being born with a low birth weight.

Asthma triggers

The symptoms of asthma can be triggered by a number of external factors as outlined below.

  • Infections of the airways and chest (respiratory infections). These infections are mainly caused by viruses. Fungi, bacteria and parasites may also be responsible for causing respiratory infections in some people.
  • Allergens, such as pollen, dust mites and animal fur or feathers can trigger asthma.
  • Airborne irritants, such as cigarette smoke, chemical fumes and atmospheric pollution may also trigger asthma.
  • Medicines, such as the class of painkillers known as nonsteroid anti-inflammatory drugs (NSAIDs), the most well-known of which are aspirin and ibuprofen, can in some cases trigger asthma. Also, a certain type of medicine, known as beta-blockers, which are used in the treatment of high blood pressure, can trigger symptoms of asthma.
  • Emotional factors - asthma can be triggered by emotional factors, such as stress or laughing.
  • Foods containing sulphites - sulphites are naturally occurring substances found in some food or drink. They are sometimes used as a food preservative. Food and drink high in sulphites include beer, wine, shrimp and many processed or 'pre-cooked' meals.
  • Weather conditions, such as cold air, may trigger asthma.

What happens during an asthma attack

The symptoms of an asthma attack begin when something triggers a biological process called inflammation. Inflammation is one of the ways that our body's natural defence system, known as the immune system, helps fight off infection against viruses or bacteria.

If your body detects an infection in the lungs, it will start the process of inflammation. White blood cells will be sent to the site of the infection to destroy the infection and to prevent it spreading. White blood cells cause the airways to swell, and produce mucus.

If you have asthma, your airways are over-sensitive to the effects of inflammation. Too much mucus is produced and your airways swell more than they should. Also, as a response to the inflammation, the muscles surrounding your airways begin to contract, making the airways narrower and narrower.

It is the combination of mucus and the swelling and narrowing of the airways that makes breathing difficult and produces the wheezing and coughing that is associated with asthma. Left untreated, the cycle of symptoms can worsen, and your airways can become totally blocked, making breathing impossible. This is a very dangerous situation that can cause death.


Your GP will normally be able to diagnose asthma by asking you about your symptoms, examining your chest and listening to your breathing.

They will want to know about your medical history and if you have a history of allergic conditions in your family.

Your GP will want to know about the circumstances surrounding the onset of your symptoms, such as when and where they occurred. They will also want to know if you have been taking any medicines, what your occupation is, and details about your work and home environment. This could help identify the possible trigger, or triggers, of your asthma.

People with asthma often lack signs of the condition, unless they are experiencing an asthma attack. This is because the degree of airway obstruction varies from person to person.

Signs that your GP will be looking for include wheezing when you breathe (although the absence of a wheeze does not rule out asthma) and an increased respiratory rate (the amount of times you breathe in and out during a minute).

Peak expiratory flow rate test

The diagnosis of asthma can typically be confirmed using a number of tests, the most popular being the peak expiratory flow rate (PEFR) test.

The PEFR test uses a small hand-held device known as a peak flow meter which can measure how much air you are able to breathe out of your lungs. A reading is taken, and you will then be given a medicine which is effective in treating asthma in the short-term. A second reading is then taken. If the reading is much higher after taking the anti-asthma medicine, then the diagnosis is normally confirmed.

You may be given a peak flow meter to take home with you, and a diary in which you can record measurements of your peak flow rate. This is a good way of recording how the symptoms of your asthma react to different circumstances.

If the symptoms of your asthma are different than normal (atypical) or you have additional symptoms, you may be referred for a chest X-ray. This is to rule out other lung conditions, such as chronic obstructive pulmonary disease (COPD) (a lung condition that is similar to asthma, but usually caused by smoking), bronchiectasis (inflammation of the airways of the lungs), or lung cancer.

Exercise-induced asthma

Your GP should be able to identify exercise-induced asthma by asking you about your symptoms in relation to exercise. Common symptoms include a cough (which normally starts six to 10 minutes after exercise) and chest tightness (appearing up to one to two hours after exercise).

Your GP will also want to know about any symptoms not related to exercise, such as coughing at night or breathlessness. This can rule out the possibility that your exercise-induced asthma is being caused by poor asthma control.

Occupational asthma

Your GP might suspect that you have occupational asthma if you report that your symptoms are better on days you do not work, or when you are on leave. Occupational asthma may also be diagnosed if you work in an industry where there is a high risk of getting the condition. Example of high-risk occupations include:

  • paint sprayers,
  • bakers and pastry makers,
  • nurses,
  • chemical workers,
  • animal handlers,
  • welders,
  • food processing workers, and
  • timber workers.

Your GP may ask you to take measurements of your peak expiratory flow rate both at work and when you are away from work, or on leave.

Your GP may then refer you to a specialist in occupational medicine, in order to confirm the diagnosis.


Treating asthma 

Once diagnosis has been confirmed, your treatment will begin with an assessment, possibly at an asthma clinic. The purpose of the assessment is to assess the pattern and severity of your symptoms and the treatment required to manage them. The plan will also investigate any possible asthma triggers. You should then be able to determine the potential impact of asthma on your daily life.

As part of the assessment, you will be encouraged to draw up a personal asthma plan following discussions with your GP or asthma nurse. The plan will include information about your asthma medicines. You will be taught how to recognise when your symptoms are getting worse and the appropriate steps to take. You will also be given information about what to do if you do have an asthma attack.

You will be encouraged to contribute to your plan by keeping a track of your symptoms and how well they respond to treatment.

You should also be alert to any associated triggers you think may be causing your asthma. Your personal asthma plan should be reviewed with your GP or asthma nurse at least once a year, or more frequently if your symptoms are severe.

As part of your asthma management you may be given a peak flow meter, so you that you can monitor your symptoms and the effects of your treatment.

Medical treatment - the stepwise approach

Treatment of asthma is carried out using what is known as 'stepwise approach', where the severity of your symptoms are assigned a 'step' from one to five, and treatment follows accordingly. As your symptoms get better or worse, you may move up or down a step in your treatment plan. The goal of treatment is to find the lowest possible step of treatment that successfully manages your condition.

Treatment involves both relieving symptoms and preventing them from reoccurring. Prevention can be achieved through the use of medicines, but lifestyle and diet also play an important role. This information below will cover the use of medicines for prevention. For further information on other methods and advice, see the 'prevention' section.

Step one - mild intermittent asthma

If your asthma symptoms are infrequent and mild, you will be given an inhaler containing a medicine called a short-acting beta2-agonist, which you should use to relieve the symptoms of asthma. Short-acting beta2-agonists work by relaxing the muscles of your airways and decreasing the amount of mucus. They also prevent the muscles around your airways tightening. Medicines that are used to relieve asthma symptoms are known as reliever medicines.

Step two - regular preventer therapy

If your asthma symptoms are more frequent, you will probably be given regular preventer therapy. This treatment is normally recommended if:

  • you have asthma symptoms more than twice a week,
  • you wake at least once a week due to your asthma symptoms,
  • you have had an asthma attack in the last two years, or
  • you have to use your short-acting beta2-agonist inhaler more than twice a week.

If you have 'step two' symptoms, you will be given a second inhaler containing a medicine called inhaled corticosteroids. You will normally be recommended to take two doses of inhaled corticosteroids a day to prevent symptoms from occurring. However, you should still use your short-acting beta2-agonist inhaler to relieve your symptoms.

Exactly how inhaled corticosteroids work is not entirely clear, but they are known to reduce the amount of inflammation in the airways and prevent asthma attacks occurring. Medicines that are used to prevent asthma symptoms are known as preventer medicines.

Smoking can reduce the effects of inhaled corticosteroids. Inhaled corticosteroids have been known to cause yeast infections (oral thrush) in the mouth, so you should rinse your mouth thoroughly after inhaling a dose.

Step 3- add-on therapy

If your symptoms are still not under control, you will be given a second preventer inhaler to take along with the first. Normally, this will contain a medicine called a long-acting beta2-agonist. These work in the same way as short-acting beta2-agonists, but they take longer to take effect and they can last up to 12 hours. Short-acting beta2-agonists only relieve asthma symptoms for three to six hours, but they start working within five minutes.

If your asthma still does not respond to treatment, the doses of inhaled corticosteroids and long-acting beta2-agonists can be increased.

You should only use your long-acting beta2-agonist inhaler in combination with your inhaled corticosteroids inhaler, and not by itself. Studies have shown that using only long-acting beta2-agonists can increase the risk of an asthma attack occurring.

Step 4 - persistent poor control

If treatment for your asthma is still not successful, the amount of inhaled corticosteroids may be increased to its maximum safe dose, and additional preventer medicines will be tried. Some possible alternatives are outlined below.

  • Leukotriene receptor antagonists - this is an oral medication (tablet) that works by blocking a chemical reaction that can lead to inflammation of your airways.
  • Theophyllines - this oral medication helps to widen your airways by relaxing the muscles around them. In some people, theophyllines have been known to cause a number of side effects, including headaches, nausea, insomnia, vomiting, irritability and stomach upsets.
  • Slow release beta2-agonist tablets - these work in the same way as long-acting beta2-agonists, but they are particularly good at preventing night-time symptoms.

Step 5 - continuous or frequent use of oral steroids

The final step involves the use of oral steroids. You will need to be referred to a specialist in respiratory conditions in order to monitor your treatment.

Long term use of oral steroids carries possibly serious side effects, so they will only be used once all other treatment options have been tried and all trigger factors have been eliminated as far as possible.

Oral steroids carry a risk if they are taken for more than three months, or if they are taken frequently (three or four course of steroids a year). Side effects can include:

  • osteoporosis (fragile bones),
  • high blood pressure (hypertension),
  • diabetes,
  • weight gain,
  • cataracts and glaucoma (eye disorders),
  • thinning of the skin,
  • easy bruising, and
  • muscle weakness.

In order to minimise the risk of taking oral steroids, you should:

  • Eat a healthy, balanced diet with plenty of calcium.
  • Maintain a healthy body weight.
  • Stop smoking (if you smoke),
  • Do not drink more than the recommended daily amount of alcohol (three to four units for men, and two to three units for women). A unit of alcohol is equal to about half a pint of normal strength lager, a glass of wine or a single of spirit (an ordinary pub measure).
  • Take regular exercise.

You will also need regular appointments to check for high blood pressure, diabetes and osteoporosis.

Exercise-induced asthma

It is likely that your general symptoms and personal asthma plan will be reviewed to determine whether your exercise-induced asthma is a result of poor asthma control. If it isn't, you will be advised to:

  • use a short acting beta2-agonist 10-15 minutes before you exercise, and again after two hours of prolonged exercise, or when you finish,
  • try to structure your exercise plan around short-burst activities,
  • exercise in humid environments, such as swimming pools, and
  • breathe through your nose to avoid hyperventilation (excessively rapid and deep breathing).

If you do not respond to treatment and you are already taking an inhaled corticosteroid, you may be given an additional preventer medicine, such as a long-acting beta2-agonist or a leukotriene receptor antagonist.

Beta2-agonists are normally regarded as a banned substance under the regulations concerning anti-doping in sport. If you are a competitive athlete, you may need to contact your relevant governing body in order to get permission to use them.

If you do not respond to treatment, you may be referred to a respiratory specialist (someone who specialises in conditions that affect breathing).

Occupational asthma

If it is possible that you have occupational asthma, you may be referred to a respiratory specialist to confirm the diagnosis. If your employer has an occupational health service, they should also be informed, along with your health and safety officer.

It may sometimes be possible to substitute or remove the substance that is triggering your occupational asthma from your workplace. If not, you should try to relocate away from your work environment as soon as possible, ideally within 12 months of your symptoms becoming apparent.

Some people with occupational asthma may be entitled to Industrial Injuries Disablement Benefit. Your local Jobcentre should be able to provide you with more information about this.

Asthma and pregnancy

Due to the changes that take place in the body during pregnancy, many women find that the symptoms of their asthma change when they are pregnant. However, it is not clear exactly what processes are involved.

Studies have shown that one third of pregnant women experienced an improvement in their asthma, one third experience a worsening of their asthma, and one third remained the same.

The most severe asthma symptoms experienced by pregnant women tend to be between the 24th and 36th week of pregnancy. Symptoms then decrease significantly during the last month of pregnancy. Only 10% of women experience asthma symptoms during labour and delivery, and these symptoms can normally be controlled through the use of reliever medicine.

You should manage your asthma in the same way as you did before you were pregnant. The medicines used for asthma have been proven to be safe to take during pregnancy, and when breastfeeding your child. The one exception is leukotriene receptor antagonists. While there is no evidence that it can harm babies during pregnancy and breastfeeding, there is not enough evidence about its safety compared with other asthma medications.

However, if you need to take leukotriene receptor antagonists to control your asthma, your GP or asthma clinic may recommend that you carry on taking it. This is because the risks to you and your child from uncontrolled asthma are far higher than any potential risk from this medicine.

Smoking during pregnancy puts both yourself and your child in danger. Smoking increases the chance of you having a severe asthma attack, which can lead to other complications, such as premature birth, low birth weight and, most seriously, the death of your child.

Smoking during pregnancy also increases the chances of your child developing asthma, being born under-weight, or being born prematurely. You should therefore quit smoking immediately. See the 'prevention' section for resources that can help you quit smoking.

Asthma attacks

As part of your assessment, and when drawing up your personal asthma plan, you will be taught to recognise the initial symptoms of an asthma attack, how you should respond, and when you should seek medical attention.

Treatment typically involves taking one or more higher doses of your reliever medicine. If the symptoms of the asthma attack progress and worsen, you may require hospital treatment. If admitted to hospital, you will be given a combination of oxygen, beta2-agonists and oral steroids to bring your asthma under control

Your personal asthma plan will then need to be reviewed, so that the reasons for your asthma attack can be identified and avoided in future.

Alternative therapies

A number of alternative therapies have been suggested for the treatment of asthma including:

  • traditional Chinese medicine,
  • acupuncture,
  • ionizers (a device that uses an electric current to charge, or ionize, molecules of air),
  • the Alexander technique (a training programme designed to change the way you move your body),
  • homoeopathy,
  • breathing exercises, including yoga and the Buteyko method (a technique involving shallow breathing), and
  • dietary supplements.

However, there is no evidence that any of these treatments are effective.



If you are a smoker and you have asthma, you should stop smoking. This will significantly reduce the severity and the frequency of your symptoms. Smoking can also reduce the effectiveness of asthma medication.


Due to the increased risk of complications, people with severe asthma are recommended to receive vaccinations for influenza (flu) and pneumococcal (a bacterium that can cause pneumonia, meningitis and infection of the blood).

Weight, diet, and exercise

Maintaining a healthy weight will help you to control your asthma more effectively. The key to maintaining a healthy weight is having a healthy diet and taking regular exercise.

A low fat, high fibre diet is recommended, including plenty of fresh fruit and vegetables (five portions a day) and whole grains. Thirty minutes of moderate exercise a day, at least five times a week, is also recommended. The exercise should be vigorous enough that it leaves your heart beating faster and you should feel slightly out of breath. Examples of moderate exercise are going for a brisk walk, or walking up a hill.

If your asthma is well managed, moderate exercise should not normally cause any problems. However, see your GP if you experience symptoms of asthma during or after exercise.

General health

As well as the factors outlined in the causes section, there are a number of other medical conditions, such as rhinitis and sinusitis, that are known to aggravate the condition. Therefore, if you get the associated symptoms of these conditions, you should report them to your GP. Treating these conditions will not necessarily make your asthma better, but it should stop it getting out of control. These conditions are listed in more detail below.


Rhinitis is an inflammation of the lining of the nose. It can be caused by an infection, such as the common cold, or can be a response to an allergen, such as pollen. The symptoms are sneezing, a blocked, stuffy or runny nose, and an itchy nose, throat and eyes.


Sinusitis is an inflammation of the small air-filled cavities inside the cheekbones and forehead. It is caused by infection. The most common symptoms are a throbbing pain that is worse when you move your head, a blocked or runny nose, and a high temperature. 

Gastroesophageal reflux disease

Gastroesophageal reflux disease is a condition of the digestive system where acid leaks back from your stomach into your oesophagus (gullet). The main symptoms are heartburn (a burning pain behind your breastbone), stomach pains, and bloating and belching. 

Sleep apnoea

Sleep apnoea is a sleep disorder where the upper airway in your throat collapses repeatedly, at irregular intervals, during sleep. You may be affected by sleep apnoea but remain unaware that you have the condition.

However, as your sleep is disrupted you should begin to experience symptoms during the day, and your partner may witness an episode of sleep apnoea, or point out other symptoms that occur at night. Symptoms include snoring, lack of concentration during the day time, and frequent awakenings during the night.


The symptoms of asthma may occur for no obvious reason. They may include:

  • feeling breathless (you may gasp for breath),
  • a tight chest (like a band tightening around your chest),
  • wheezing (a whistling sound when you breathe), and
  • coughing, particularly at night (this is less common in adults than in children).

The severity and duration of the symptoms of asthma are often variable and unpredictable, and are sometimes worse during the night or with exercise.

The symptoms of a severe asthma attack often develop slowly, taking between six and 48 hours to become serious.

You should remain alert for any signs of worsening symptoms. These include:

  • a drop in your peak expiratory flow rate (see the 'diagnosis' section for more information),
  • an increase in your pulse rate,
  • an increase in wheezing, and
  • feeling agitated or restless.

If you notice your symptoms getting worse, do not ignore them. Instead, contact your GP or asthma clinic.

Typical symptoms of a severe asthma attack include:

  • your symptoms will get worse quickly,
  • breathing and talking will be difficult,
  • your pulse may race,
  • your lips and/or your finger nails may turn blue,
  • your skin may tighten around your chest and neck, and
  • your nostrils may flare as you try and breathe.

You should immediately seek medical help if you have symptoms of a severe asthma attack.