Why does it itch after a bedbug bite? - briefly
Bedbug saliva injects proteins that provoke an immune response, leading to histamine release and localized inflammation. The swelling and irritation from this reaction cause the characteristic itching.
Why does it itch after a bedbug bite? - in detail
The itching that follows a bed‑bug bite results from the body’s immune reaction to substances injected by the insect. When a bed bug pierces the skin, it releases saliva containing anticoagulants, anesthetics, and proteins that prevent blood clotting and reduce pain. These foreign proteins are recognized as antigens, prompting the immune system to release histamine and other inflammatory mediators.
Histamine binds to receptors on nerve endings, creating the characteristic pruritic sensation. The reaction usually appears within a few hours to a day after the bite and can persist for several days, depending on individual sensitivity and the amount of saliva introduced.
Several factors influence the intensity of the itch:
- Allergic sensitivity: People with higher IgE levels experience stronger histamine release.
- Number of bites: Multiple punctures increase the total antigen load, amplifying the response.
- Location on the body: Areas with thinner skin or richer nerve supply, such as the wrists or ankles, produce more pronounced sensations.
- Secondary irritation: Scratching damages the epidermis, allowing bacterial entry and prolonging inflammation.
The inflammatory cascade also involves cytokines such as interleukin‑4 and interleukin‑13, which recruit additional immune cells and sustain the pruritic cycle. Over time, the skin may develop a raised, red, or vesicular lesion that resolves as the immune response diminishes and the tissue repairs.
Effective management targets the histamine pathway and skin integrity. Antihistamine tablets or topical creams reduce receptor activation, while corticosteroid ointments suppress cytokine production. Keeping the area clean and avoiding further trauma prevents secondary infection and accelerates healing.