Allergy (english)

Allergy, a condition of hypersensitivity in certain persons or animals to substances harmless to most individuals. Some people have characterized allergy as immunity “gone wrong.” In the immune reaction, contact with a disease-producing microorganism or a toxin prompts an individual to build up antibodies (proteins related to globulin serum) against the offending organism or toxin so that he or she will be protected against further exposure. All normal people are able to produce such protective antibodies, but in some the capacity to differentiate potentially harmful substances from harmless ones is absent. These persons produce antibodies against one or many inoffensive substances and thus are said to be allergic. When an antibody reacts with an antigen (a substance that stimulates the formation of antibodies) an allergic reaction results.