Asthma (Hansard, 2 February 1998)

§ Baroness Jay of Paddington

It is not known what causes asthma, although it appears to involve an interplay between genetic and environmental factors. A range of trigger factors can bring on asthma attacks in individual people, once they have become sensitised to them. Asthma triggers vary from person to person. They include substances in the environment which induce allergic reactions, such as house dust mite dung, pollen and fungal spores, outdoor air pollution, environmental tobacco smoke, respiratory infections and exercise. Stress, excitement or emotional upset may also bring on symptoms in some people.