Why does a bedbug bite itch? - briefly
Bedbug bites provoke itching because the insects inject saliva containing anticoagulant proteins that stimulate a localized immune response, releasing histamine and other inflammatory mediators. The resulting reaction causes redness, swelling, and the characteristic urge to scratch.
Why does a bedbug bite itch? - in detail
Bedbug bites produce itching because the insect injects saliva containing anticoagulants, anesthetics, and enzymes while feeding. These substances are foreign to the human body and trigger an immune reaction. The immune system releases histamine and other inflammatory mediators at the bite site, causing vasodilation, swelling, and the characteristic pruritus.
The intensity of the itch depends on several factors:
- Composition of saliva – proteins and enzymes act as allergens, varying among bedbug populations.
- Host sensitivity – individual differences in immune response determine the magnitude of histamine release.
- Exposure duration – multiple feeds or prolonged feeding increase the amount of saliva deposited, amplifying the reaction.
- Secondary factors – scratching can damage skin, leading to bacterial colonization and prolonged inflammation.
The itching often appears several minutes to a few hours after the bite, reflecting the time required for the immune system to recognize the salivary antigens and mobilize inflammatory cells. In some cases, a delayed hypersensitivity reaction occurs, producing a larger, more persistent wheal that may last days.
Histamine binds to H1 receptors on sensory nerve endings, generating the sensation of itch. Antihistamines block these receptors, reducing the symptom. Topical corticosteroids suppress the local immune response, limiting swelling and erythema.
Understanding the biochemical and immunological mechanisms behind the pruritic response clarifies why bedbug bites are notably irritating and guides effective treatment strategies.