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Asthma: What is it?

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 6 minutes read

Asthma is a chronic disease in which sufferers have repeated attacks of difficulty in breathing and coughing. People who have asthma have inflamed airways that become swollen and very sensitive. They tend to react strongly to certain inhaled substances and when the airways react, the muscles around them tighten. This narrows the airways, causing less air to flow into the lungs and the swelling can worsen, making the airways even narrower. Cells in the airways might make more mucus than usual. Mucus is a sticky, thick liquid that can further narrow the airways.

This chain reaction can result in asthma symptoms. Symptoms can happen each time the airways are inflamed.

People of all ages get asthma but 50 per cent of sufferers are children, mostly boys, under 10. Among adults, women are more likely to develop asthma than men.

Asthma can be triggered by external things such as irritants in the atmosphere which are breathed in, or by internal reactions within the body that have been caused by external triggers. All asthma patients are affected by a number of things that are referred to as irritants - these include exercise, cold, smoke, scents and pollution. Common irritants or allergens include pollen, dust, animal fur, mould and some kinds of food. A virus or bacteria, chemical fumes or other substances at the workplace and certain medicines, e.g. aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), may also cause asthma.

To develop asthma, people seem to need to have been born with a predisposition (a tendency) to the disease but it often does not reveal itself until they have been exposed to some asthma irritants. Asthma is common in childhood, but many outgrow it by their teens. Most cases are mild and managed at home with inhalers, but a few people suffer a severe form, where they may require input from a specialist. You may need constant treatment, or it may flare up from time to time.

Doctor’s advice

What are the symptoms?

There are four key symptoms to look out for: chest tightness, feeling short of breath, a cough or a wheeze (a high-pitched sound when you breathe out). You may find you feel short of breath overnight or first thing in the morning, as this correlates with fluctuations of a hormone called cortisol. Symptoms might come and go. These symptoms also signal a flare-up of asthma that's previously been quiet or well-controlled.

What triggers should I look for?

Allergic asthma is commonly triggered by pollen, which appears in the spring and summer, house dust mite and pet dander. You may not notice straight away, it may take time to become sensitised and for symptoms to appear. Non-allergic asthma is caused by environmental irritants such as mould, pollution, smoking and possibly industrial chemicals if used at work (occupational asthma). In these cases, it's not so much allergens as chemicals that irritate in susceptible people.

Some people only get asthma during exercise or with a cough and cold, and others find asthma only appears in winter months. Stress is a trigger for some, and hormonal changes, such as puberty, pregnancy or the menopause, causes a change to asthma in others.

You may have other atopic conditions, such as hay fever, eczema or food allergies, and these may run in your family. This makes allergic asthma more likely. How is a diagnosis made?

A diagnosis is made in two ways: a trial of treatment (a reliever inhaler) is assessed with your symptoms and peak flow scores. Or your doctor may organise lung function tests, usually with your practice nurse, where a machine records how well you exhale. On the basis of either of these or both, you will likely be prescribed two types of inhaler, a reliever inhaler for any symptoms and a preventer inhaler for daily use. They will review you regularly to check progress, changing doses or medications as needed, until your asthma has stabilised.

What treatments are used in asthma?

There are three main groups of medications. These are:


A reliever inhaler is taken ‘when needed’ to ease symptoms. The medicine in reliever inhalers (a bronchodilater) relaxes the muscle surrounding the airways. This makes the airways open wider, and symptoms quickly ease as oxygen can enter the airways easier. Usually blue in colour they are used whenever you notice symptoms, or if physical activity is a known trigger, take reliever inhaler before starting the physical activity. If you need to use reliever medicine for asthma symptoms more than three times a week you should see your doctor.


A preventer inhaler is taken every day to prevent symptoms from developing. These are usually brown or orange inhalers and are taken every day, even when you feel well. This medicine (a corticosteroid) works by reducing the swelling and inflammation in the airways. Taking your preventer each day, helps to keep your asthma under control, as corticosteroids help reduce the inflammation inside the airways. This also means you should not need to take reliever medicine most days.

Long acting Bronchodilator

A long acting inhaler used to relieve the symptoms of asthma – known as a bronchodilator - can be recommended in addition to a preventer inhaler. Asthma is a two-process condition (inflammation and bronchoconstriction) so to help alleviate both, a preventer and long acting bronchodilator are needed. If you have found that your symptoms are not fully controlled by the preventer (corticosteroid inhaler) alone ask your doctor about long acting bronchodilators. The medicines in these inhalers work in a similar way to ‘relievers’, but work for up to 12 hours. They include salmeterol and formoterol. (Some brands of inhaler contain a steroid plus a long acting bronchodilator for convenience.)

Leukotriene receptor antagonists are another type of treatment sometimes used in asthma. Leukotrienes are released from the lungs in people with asthma, causing inflammation and increased mucus production in the airways. They also cause the muscles lining the airways to contract, which narrows the airways. All of this makes it difficult for air to get in and out of the lungs. Leukotriene receptor antagonists block leukotriene receptors in the lungs and, as a result, block the action of the leukotrienes. This prevents the excess mucus production, inflammation and narrowing of the airways and so prevents asthma attacks. It’s also useful for preventing asthma triggered by exercise.

Combination inhalers have been the mainstay of asthma treatment for a number of years and many patients feel their asthma is much better controlled on these combination inhalers and compliance is much better as they only need to use one inhaler rather than two. Easy to use, they can also be useful in visually impaired patients and those who find using two or even three inhalers difficult to remember.

Always treat asthma earlier rather than later - fast, effective treatment may stop your symptoms from getting worse. If you’re worried and unable to breathe properly, especially after taking your reliever medicine, see your doctor or contact the emergency services immediately.

When should I see my doctor?

With these symptoms you should book an appointment with your doctor to have this assessed. They will listen to your symptoms and any triggers, take your vital signs and listen to your chest. They may suggest you keep a symptom diary, record your peak flow with a special device, and may give you an inhaler to trial which should relieve symptoms.

They will review your diary and symptoms after a couple of weeks to see if they’ve improved.

What are the warning signals of worsening attacks?

Inhaled medicines appear less effective than usual.

  • Symptoms of cough or wheeze on exertion.
  • Night-time wakening with wheeze or cough.
  • Fall in the peak flow meter reading (a peak flow meter is a simple device that measures the maximum speed at which a person can breathe out).

What are the danger signals of asthma?

  • Bluish skin colour and gasping breath.
  • Exhaustion so severe that speech is difficult or impossible.
  • Confusion and restlessness.

If any of these occur, seek urgent medical attention.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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