Hypersensitivity is the medical term for a hypersensitivity reaction, an abnormal immune response, which simply means that the body’s defense cells overreact, leading to a conflict between the body and the defense cells, also known as a paradoxical reaction. Hypersensitivity reactions can lead to a number of diseases. Some of the more common clinical diseases are autoimmune hemolysis, but also systemic lupus erythematosus, and other rheumatic and rheumatoid diseases, all of which are hypersensitivity reactions and are abnormal pathological conditions. In clinical practice hypersensitivity reactions are very difficult to treat, and the application of biological agents and hormones is advocated for symptomatic management. There is no complete cure for hypersensitivity reactions in the human body, and the only way to alleviate the condition is through medication or other means.