Anti-allergic Drugs

Abstract

ALLERGY is defined as a disease following a response by the IMMUNE SYSTEM to an otherwise innocuous antigen. Allergic diseases include allergic rhinitis, atopic dermatitis, systemic ANAPHYLAXIS, food ALLERGY, allergic ASTHMA and acute urticaria and are mediated by unwanted type-I HYPERSENSITIVITY reactions (see Chap. A9) to extrinsic ALLERGENS like pollen, house dust, animal dander, drugs and insect venom. These diseases are characterised by the production of IgE ANTIBODIES to the allergen that binds to the high-AFFINITY IgE RECEPTOR, FcεRI, on mast cells and BASOPHILS. Binding of allergen to IgE cross-links these RECEPTORS and causes the release of chemical mediators from MAST CELLS, leading to the development of a type-I HYPERSENSITIVITY reaction (Fig. 22.1). This acute response is often followed by a late and more sustained inflammatory response characterised by the recruitment of other EFFECTOR CELLS such as EOSINOPHILS and T helper type-2 (Th2) LYMPHOCYTES. Among the mainstays in the drug treatment of allergic INFLAMMATION, glucocorticosteroids remain the most potent inhibitors, and the reader is referred to Chap. C13 for detailed discussion of these drugs. The use of SPECIFIC IMMUNOTHERAPY in severe allergies is considered in Chap. C5. This present chapter focuses on anti-allergic drugs that specifically TARGET the activation of the mast cell or block the effects of its chemical mediators, in particular HISTAMINE.