Immediate hypersensitivity reactions generally occur within what time frame after exposure?

Immediate hypersensitivity reactions, also known as type I hypersensitivity reactions, typically occur within minutes after exposure to an allergen. This rapid response is primarily mediated by immunoglobulin E (IgE) antibodies, which bind to allergens and trigger the release of histamine and other mediators from mast cells and basophils. The release of these substances leads to various clinical symptoms, such as itching, swelling, and bronchoconstriction, commonly seen in allergic reactions like anaphylaxis, asthma, or hay fever.

Timing is a crucial distinguishing factor for immediate hypersensitivity reactions, as they are characterized by this swift onset compared to other types of hypersensitivity reactions, which may take hours, days, or even weeks to manifest. This understanding is essential for diagnosing and managing allergic reactions effectively.