Why does the site of a bedbug bite itch? - briefly
Bedbug saliva introduces anticoagulant proteins that provoke an immune response, leading to histamine release and localized itching. The resulting inflammation typically subsides within a few days as the body clears the irritants.
Why does the site of a bedbug bite itch? - in detail
Bedbug saliva contains a complex mixture of proteins, anticoagulants, and anesthetic compounds that are injected while the insect feeds. These substances trigger the body’s immune response, leading to the characteristic itching.
When the saliva contacts the skin, antigenic proteins are recognized as foreign, prompting mast cells to release histamine and other inflammatory mediators. Histamine binds to receptors on sensory nerve endings, generating the sensation of pruritus.
The inflammatory cascade also involves cytokines such as interleukin‑4 and interleukin‑13, which recruit additional immune cells and amplify the reaction. This prolonged response can keep the bite area itchy for several days.
Factors that intensify the itch include:
- Individual sensitivity: Some people produce larger amounts of IgE antibodies, causing a stronger histamine release.
- Bite location: Areas with thin epidermis (e.g., forearms, ankles) allow easier penetration of saliva components, leading to more pronounced symptoms.
- Secondary irritation: Scratching damages the epidermal barrier, exposing nerve endings and promoting further histamine release.
The combination of immediate histamine effects and delayed cytokine-driven inflammation explains why the bite site remains itchy long after the insect has detached.