Sensitization to chemicals can be defined as changes in the organism, usually the immunochemical system, by exposure to a chemical such that further chemical exposure leads to recognition by the organism. Such recognition will lead to a response that is marked by a greater reaction at lower doses than what would be observed in non-sensitized individuals. Inhulation of the antigen/allergen in an individual previously sensitized leads to an allergic reaction, such as rhinitis or conjunctivitis. If the skin is sensitized, as in allergic contact dermatitis, then contact will cause an oedematous response and/or a rash. Pulmonary sensitization manifests itself through bronchial constriction or obstruction Some chemicals can produce different types of "allergy" There are various known and hypothesized mechanism for sensitization. There are also host susceptibility factors, including genetic predisposition, which will play a role in sensitization and in disease manifestation
