Allergy: Introduction
Allergy is an immune response to a foreign antigen that results in inflammation and organ dysfunction. Allergies range from the life-threatening to the annoying and include systemic anaphylaxis, laryngeal oedema, transfusion reactions, bronchospasm, vasculitis, angioedema, urticaria, eczematous dermatitis, hay fever, rhinitis, and conjunctivitis. Allergic responses may be initiated and sustained by occupational exposures to allergens, by foods, animals, fungal spores, metals, rubber products, and other agents. Allergies can be regarded as the hypersensitive reactions of the immune system to various allergens. A substance may be an allergen for one person, while just a normal substance for the other. Allergies are individual responses and are not communicable.