Hypersensitivity refers to an exaggerated or abnormal immune response to a harmless antigen, leading to inflammation, tissue damage, or other immune-related reactions. There are different types of hypersensitivity reactions, categorized into four main types (Type I, Type II, Type III, and Type IV), each involving different mechanisms and immune responses. Hypersensitivity can manifest in various forms, such as allergies, autoimmune diseases, and other immune-mediated conditions. Understanding the mechanisms of hypersensitivity reactions is crucial for developing effective treatments and interventions for individuals affected by these conditions.