Asthma: checklist of common triggers
An asthma ‘trigger’ is anything that brings on or aggravates asthma symptoms. Common asthma triggers can be divided into roughly 2 groups:
- substances called allergens that set off an allergic reaction in the body, a symptom of which may be asthma; and
- other substances and circumstances that aggravate asthma without involving an allergic reaction.
Knowing what your asthma triggers are, and then avoiding them, are important aspects in controlling your asthma.
Allergens
- House dust mites. These are tiny creatures related to ticks and spiders that live by the tens of thousands in the dust of our houses, especially if the air is warm and humid. Inhaling dust mite droppings can trigger asthma symptoms.
- Pollen (usually from grasses, trees or weeds). As well as causing hay fever in people with a pollen allergy, pollen can also trigger asthma attacks in susceptible people. In Australia, pollen levels in the air are at their highest in summer, although grass pollens can cause a problem all year round for people living in the warmer northern regions of the country. Many of the pollens that trigger asthma are from introduced plant species such as ryegrass, the weeds Paterson’s curse and pellitory (‘asthma weed’), and street trees such as oaks, elms and birch. A phenomenon called ‘thunderstorm asthma’ can happen in humid conditions, for example before a storm, when the high humidity causes pollen grains to break apart and release tiny starch granules, which can be breathed into the lungs more easily than larger, intact pollen grains, resulting in an increase in the number of people with asthma symptoms around the time of a storm.
- Animal dander (skin scales or flakes from the hair or feathers of animals). Exposure to allergens from pets, especially cats, can trigger or worsen asthma symptoms. Animal allergens are present in household dust, so direct contact with an animal is not always needed for asthma symptoms to be triggered in those allergic to animal dander.
- Moulds or fungi. Alternaria is an outdoor fungus that is found on plants. It is known to trigger asthma in drier inland areas of Australia, especially in agricultural regions when crops are harvested. Cladosporium is a plant mould that can also trigger asthma, but is more common in cooler areas of southern Australia and can be a problem when grass is mown.
Moulds that grow indoors — for example, on damp walls, especially in corners — can also trigger asthma. - Cockroach allergen. This allergen, which is found in cockroach droppings, can build up in the dust of houses that have cockroaches present, and can trigger asthma symptoms.
- Food allergy. Being exposed to a food to which you are allergic can trigger asthma symptoms — often accompanied by other symptoms such as a rash. The foods that can trigger allergic asthma attacks include nuts, eggs, milk, shellfish, fish, or seeds (e.g. sesame seeds). Food allergy is not a common trigger of asthma, but in some cases — nut allergy, in particular — a severe and life-threatening allergic reaction (anaphylaxis), rather than asthma alone, can occur.
- Occupational allergens. Some adults can develop an allergy to substances that are present in the air at their workplace and can trigger asthma symptoms, for example, flour, latex and wood dusts. Some other workplace asthma triggers, such as isocyanates, which are used in the manufacture of pesticides, polyurethane foam, plastics, paints and varnishes, may trigger asthma symptoms either via an allergy or because they irritate the airways directly.
Non-allergic triggers
- Viral respiratory infections. Viral infection of the upper airways is a common trigger of asthma, especially in children, and often leads to a period of persistent coughing.
- Medicines. Asthma can be triggered by certain medicines such as aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), as well as COX-2 inhibitors, which are often used for arthritis; heart and blood pressure medicines called beta blockers; certain eye drops; and complementary medicines, including echinacea and Royal Jelly, which has even resulted in death in some people with asthma.
- Air pollution and other inhaled irritants. Exhaust fumes, in particular from diesel engines, are thought to contain particles that stick to common airborne allergens, for example broken-up pollen grains, and make them easily breathed into the lungs, where they can trigger asthma symptoms. Bushfire smoke is another trigger of asthma symptoms.
Cigarette smoke, some perfumes, and the fumes from paints and cleaning fluids can also provoke asthma symptoms. - Exercise. Exercise is a very common asthma trigger and may be the only trigger in some people with asthma. It is thought that breathing in cold, dry air while needing to breathe hard, as occurs with vigorous exercise, are the key elements of this trigger.
- Emotions. Strong emotions such as stress, anxiety, and hearty laughing or crying can trigger asthma symptoms in some people.
- Heartburn (reflux). A small amount of stomach acid refluxing or regurgitating into the lower oesophagus, as occurs in heartburn, is a potential asthma trigger.
- Cold air and ambient temperature changes. Breathing in cold air can trigger asthma symptoms, for example, outside air on a cold day or cold night-time air in your bedroom.
- Food additives. Some food additives can trigger asthma. These include sulphur dioxide and sulphites (food additive numbers 220 to 228) — found in sausages, dried apricots, wine and many ‘fast foods’. Sulphur dioxide (additive number 220) is the one thought most likely to trigger asthma symptoms. Tartrazine (a food dye, additive number 102) is another possible trigger of asthma, although research has not shown a firm link between tartrazine and asthma symptoms.
Glutamates are found in many foods naturally or are added as flavour enhancers (food additive numbers 620 to 625). One of these additives, monosodium glutamate (MSG; additive number 621), has been studied a great deal; however, research has not clearly shown that MSG can provoke asthma symptoms.
At the time of writing, there is not enough evidence to suggest that people with asthma should routinely avoid food additives without having first been referred by their doctor to an allergy specialist.
Last Reviewed: 28 August 2007
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