Type I Hypersensitivity (Immediate Hypersensitivity)

Type I hypersensitivity, also known as immediate hypersensitivity, occurs when the immune system overreacts to harmless substances like pollen, pet dander, or certain foods. This response is triggered by the release of antibodies called IgE, which bind to allergens and cause mast cells to release chemicals like histamine. These chemicals lead to symptoms such as sneezing, itching, hives, or even severe reactions like anaphylaxis. This hypersensitivity can manifest quickly, often within minutes of exposure to the allergen, and highlights how the body can sometimes misidentify safe substances as threats.