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

There is a huge variety of these triggers that have been reported by patients including dogs, cats, tobacco smoke, cold air, exercise, being upset, anxiety, and stress, taking aspirin, dust, fumes and even laughter.

However, particularly severe attacks which can lead to hospital stays usually occur following a virus infection in the nose or chest.

It is important that an asthmatic and their doctor identify the one or more triggers that can make their asthma worse and limit exposure to them through daily management of the disease.

The most common triggers for asthma include:

Allergens

 The skin, hair, or feathers of animals, such as cats, dogs, etc.

 Dust mites found in house dust.

 Cockroaches.

 Tree and grass pollen.

 Mold.

Irritants

 Cigarette smoke.

 Air pollution .

 Drastic weather changes

 Changes in air temperature, for example, if you move from warm indoor air to cold air outdoors.

 Cooking or paint oders

 Scented products, candles, air fresheners, etc.

 Allergens that you are exposed to at your place of work such as chemicals, dusts, smells, etc.

Others

 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 are used in medical tests to produce a minor and controlled asthma attack to determine the extent of the disease. 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 the patient's airways that can be very useful to the doctor.

 The inhalers used to treat asthma can causes symptoms. Some powder inhalers can cause tightness in the chest and the lubricants in pressurised aerosol inhalers can cause irritation of air passages, and can bring on an asthma attack.

 Some medicines such as aspirin or other painkillers and beta blockers that are used for high blood pressure or heart disease.

 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 and drink such as 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.

 Gastro-oesophageal reflux, where stomach acid rising up the gullet 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.

 Exercise.

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