Asthma is a chronic lung condition that is characterized by difficulty in breathing. People with asthma have extra sensitive or hyper-responsive airways.

During an asthma attack, the airways become irritated and react by narrowing and constructing, causing increased resistance to airflow, and obstructing the flow of the air passages to and from the lungs.

The words “trigger factors”, or “triggers” of asthma are used for the things which can cause an attack in someone who already has asthma.

Many things seem to be able to bring on, or trigger, an asthma attack, and the causes and triggers vary greatly from person to person. Dogs and cats cause asthma attacks in some people. While for others, tobacco smoke, cold air, exercise and even laughing can trigger attacks too.

Some people with asthma report that the asthma attacks are worse when they are upset, anxious or under stress. Some people get asthma if they take aspirin or other painkillers, and some get asthma from dusts or fumes at work.

Really bad asthma attacks, which force people to go into hospital, often happen after a virus infection of your nose or chest.

The most common triggers for asthma include:

  • Allergens

  • Animal dander from the skin, hair, or feathers of animals, such as cats, dogs, etc.

  • Dust mites (contained in house dust)

  • Cockroaches

  • Pollen from trees and grass

  • Mould (indoor and outdoor)

  • Irritants

  • Cigarette smoke

  • Air pollution

  • Changes in weather

  • Cold air, for example, if you move from warm indoor air to cold air outdoors.

  • Strong odours from painting or cooking

  • Scented products

  • Irritants or allergens that you may be exposed to at your work such as special chemicals or dusts.

  • Breathing tests. Just as the faster breathing in exercise can bring on attacks, the faster and deeper breathing you have to do for most breathing tests can bring on quite a noticeable narrowing of air passages, and can bring on an asthma attack.

Histamine or methacholine aerosols. In specialised tests doctors use an inhaled mist of these substances to measure how irritable your air passages are. In asthma they are more irritable than normal.

During allergic or asthmatic reactions cells in the lungs release histamine. Methacholine mimics the effect of a substance (acetylcholine) released by nerves in the lung during asthma.

Both substances cause an asthma attack in anyone who breathes enough of them, but people who have asthma will get an attack from a much smaller amount. In the test, the amount of asthma produced is small and very bearable, and it wears off quickly. The result gives a measurement of the irritation in a persons airways that can be very useful.

Irritants in asthma inhalers. For example, some powder inhalers can cause a small amount of chest tightness. Pressurised aerosol inhalers need to have a lubricant and this can cause irritation of air passages, and can bring on an asthma attack.

Some drugs, especially medicines called beta blockers used for high blood pressure or heart disease. Medications such as aspirin or other painkillers.

Sulphur dioxide was previously used as a preservative in soft drinks and wine. This can cause chest tightening within seconds of drinking, or even breathing the air above such a drink.

Sulphites in food (dried fruit) or beverages (wine). For example, sodium metabisulphite (E220227) may trigger asthma, but not via an allergic reaction. It can be found in wine, home-brewed beer, fizzy drinks, prepared meats and prepared salads.

Indigestion, with stomach acid rising up into your gullet. This is called gastro-oesophageal reflux, or more commonly, acid reflux. This causes heartburn and can worsen asthma symptoms, especially at night.

Infections of the lining of the breathing passages, such as colds and flu.

Laughing or crying.


Strong emotional stress. People with asthma often say that their asthma gets worse if they are upset, crying, or under stress.

This is not a complete list of all the things that can trigger asthma.

In addition, people differ in which of these things cause the most asthma, and some people may have trouble with one or more of these triggers. It is important for you to identify what triggers your asthma, so that you can avoid or minimise your exposure to it. Your doctor can help you with this.

Nevertheless, they all cause irritation or narrowing of the air passages in asthma sufferers.

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