He refers to the difference from a normal immune response, which differs from a normal immune response in that the body recognizes and eliminates the antigen while causing dysfunction or pathological damage to the organism. Some people are allergic to fish and shrimp and hair dye. Hypersensitivity refers to the re-exposure of the sensitized organism to the same antigen, resulting in physiological dysfunction or pathological damage to the organism. Very few people are re-sensitized to certain drugs.