hypersensitivitetsreaksjon

Hypersensitivitetsreaksjon describes an exaggerated or inappropriate immune system response to a substance that is normally harmless to most people. This reaction occurs when the immune system mistakenly identifies a foreign substance, known as an allergen, as a threat and initiates a defense mechanism. These reactions can range from mild, such as a skin rash or itching, to severe and life-threatening, like anaphylaxis.

There are four main types of hypersensitivity reactions, classified by Gell and Coombs. Type I, also known as immediate hypersensitivity, is the most common and involves IgE antibodies. Examples include allergies to pollen, food, or insect stings. Type II reactions, or cytotoxic hypersensitivity, involve antibodies binding to cell surfaces, leading to cell destruction. This can occur in transfusion reactions or certain autoimmune diseases. Type III reactions, immune complex hypersensitivity, result from the deposition of antigen-antibody complexes in tissues, triggering inflammation. Serum sickness is a classic example. Type IV reactions, delayed hypersensitivity, are cell-mediated and develop over 24-72 hours. Contact dermatitis from poison ivy or a positive tuberculosis skin test are examples.

The severity and specific symptoms of a hypersensitivitetsreaksjon depend on the type of reaction, the allergen involved, and the individual's immune system. Diagnosis often involves medical history, physical examination, and specific tests such as skin prick tests, blood tests for antibodies, or challenge tests. Management typically focuses on avoiding the allergen, using antihistamines or corticosteroids to reduce inflammation, and in severe cases, epinephrine for anaphylaxis. Understanding hypersensitivity is crucial for diagnosis and effective treatment of allergic and autoimmune conditions.