Mosquito bites itch because the itch is an allergic reaction to proteins in mosquito saliva. When a mosquito bites, it injects saliva into the skin to prevent blood clotting and allow easier blood flow. The human immune system is hypersensitive to some of these proteins, triggering the release of histamine. Histamine causes blood vessels to dilate and promotes inflammation at the site of the bite, which in turn activates nerve endings and produces the sensation of itching. This is a protective immune response aimed at fighting the foreign substances introduced by the mosquito's saliva.
Why Mosquito Bites Itch
- Mosquitoes inject saliva containing anticoagulant proteins to facilitate blood feeding.
- The human immune system treats these proteins as allergens, triggering an allergic reaction.
- This reaction releases histamine, which causes inflammation and activates itch sensors in the skin.
Biological Mechanism
- Histamine binds to specific receptors on nerve endings, sending itch signals to the brain.
- Other immune responses also may contribute, including IgE-mediated hypersensitivity and the release of other inflammatory chemicals like cytokines and leukotrienes.
- The itch sensation warns the body of a potential threat and prompts actions like scratching (though scratching can worsen inflammation).
Summary
The itching from mosquito bites arises primarily because of the immune system's response to mosquito saliva proteins, causing histamine release and inflammation, which stimulates nerve endings and causes the sensation of itchiness.
