Allergen immunotherapy is the repeated administration of allergen extracts to allergic individuals in order to provide long-term relief of symptoms and improvement in quality of life during subsequent natural allergen exposure. Allergen immunotherapy is highly effective in IgE-mediated disease in patients with a limited spectrum (1 or 2) of allergies. Immunotherapy is indicated in allergic rhinoconjunctivitis and allergic asthma due to seasonal pollinosis and in patients with perennial disease and sensitivity to house dust mite and animal danders. In patients who develop systemic anaphylactic reactions to wasp/bee stings, immunotherapy may be life-saving and has a major impact on quality of life of venom-allergic subjects. Unlike anti-allergic drugs, immunotherapy has been shown to modify the underlying cause of the disease, with proved long term benefits. Allergen immunotherapy may be combined with appropriate allergen avoidance strategies. Immunotherapy is not competitive with the conventional use of pharmacotherapy and should be administered in the context of general advice regarding overall disease management (