Asthma - allergies and triggers

An asthma allergen is a substance which is harmless to most people but which starts a complex inflammatory reaction in people with asthma. This involves the release of chemicals including histamine which triggers the immune system. The airways become inflamed and swollen and go into spasm (bronchoconstriction). This causes breathlessness and wheeze.

For some people external triggers can cause similar reactions to occur.


View text alternative

The most common allergens are:

  • Animal allergens: found in pet saliva, flakes of skin, fur and urine are potent triggers of asthma symptoms.
  • House Dust Mite: Many people are sensitive to the droppings of house-dust mites. They live in the dust that builds up around the house, particularly in carpets, bedding, soft furnishings and soft toys.
  • Pollen: People with asthma find pollen can be a common trigger.
  • Mould spores: usually found in damp conditions around the house.

Other triggers:

  • Weather conditions –too hot, too cold, thunderstorms.
  • Air pollution: from chimneys, car exhausts and open fires or bonfires.
  • Emotional state: laughter or stress can be a trigger for some people.
  • Exercise induced: vigorous or sudden increase in exercise (most people can be taught how to exercise safely and exercise is useful for overall health).
  • Strong chemical smells: such as air fresheners, scented candles or spray deodorant.
  • Food allergies: such as shellfish or nuts may be related for some people with asthma.
  • Tobacco smoke: including second hand smoke.