Not AvailableThe environment is used as a broad umbrella term for all sources of allergens which may cause allergic hypersensitive reaction of the immune system of humans and animals. Hypersensitivity is the name given to a state in which an immune response damages the body's own tissues. It is a process of reactions of antigen with antibody or sensitised lymphocytes that are harmful to the host. When an adaptive immune response occurs in an exaggerated or inappropriate form causing tissue damage, the term ‘hypersensitivity ’is applied. There are four or five types of hypersensitivity that are often described. Research has focused on understanding each hypersensitivity reaction to ensure appropriate therapeutic recommendations. This article elucidates the details of different types of hypersensitivities and different methods of detection.Not Availabl