The incidence of asthma is rising rapidly, and the reasons include:
- increase stress on the immune system duet to factors such as greater chemical pollution in the air, water, insect allergens (mostly from dust mites), and food
- earlier weaning and earlier introduction of solid foods to infants
- food additives
- higher incidence of obesity
- genetic manipulation of plants, resulting in food components with greater allergenic tendencies; in addition, certain genetic variables may make certain individuals more susceptible to asthma
Asthma has been divided into two categories: extrinsic and intrinsic. Extrinsic or atopic asthma is generally considered and allergic condition with a characteristic increase in IgE – the antibody produced by white blood cells that can bind to specialized white blood cells, known as mast cells, and cause the release of mediators such as histamine. Intrinsic asthma is associated with a bronchial reaction that is due not to an allergy but rather to such factors as chemicals, cold air, infection etc. Both extrinsic and intrinsic factors trigger the release from mast cells of chemicals that mediate inflammation. The inflammatory mediators are responsible for the sings and symptoms of asthma.