Why does the body itch after a bed bug bite? - briefly
The bite injects saliva with anticoagulant proteins that provoke an immune response, causing histamine release that activates itch‑sensing nerves. The sensation intensifies within hours and fades as the body clears the irritants.
Why does the body itch after a bed bug bite? - in detail
Bed bugs feed by inserting a needle‑like mouthpart into the skin and delivering saliva that contains anticoagulants, anesthetics, and a mixture of foreign proteins. These substances are not recognized as self by the immune system, prompting an immediate defensive response.
The foreign proteins trigger mast cells and basophils in the dermis to release histamine and other mediators such as prostaglandins and leukotrienes. Histamine binds to receptors on sensory nerve endings, lowering the threshold for activation and producing the characteristic pruritic sensation.
The cascade continues with cytokine release, recruitment of additional immune cells, and localized edema. The swelling stretches nerve fibers, intensifying the itch. The reaction may be delayed; initial exposure often produces a mild or absent sensation, while subsequent bites elicit a stronger response due to sensitization.
Individual sensitivity varies. Some people develop a rapid, pronounced reaction after a single bite, whereas others experience only minimal irritation even after repeated exposure. The degree of itching correlates with the amount of saliva injected and the host’s immunologic profile.
Scratching disrupts the epidermal barrier, allowing bacterial colonization and prolonging inflammation. Secondary infection can amplify pruritus and delay resolution.
Management focuses on interrupting the histamine pathway and reducing inflammation: oral antihistamines, topical corticosteroids, or calamine lotion provide symptomatic relief. Maintaining skin hygiene and avoiding further bites prevent exacerbation.