The swelling that results from a mosquito bite is the body’s autoimmune response to the components in the saliva that the mosquito injects.
More Info: In order to circumvent the host’s hemostasis response (arrest of bleeding), the mosquito injects an anti-coagulant through its saliva into the bloodstream of the host. The swelling experienced after the bite is the body’s autoimmune response to the proteins found in the saliva.
Mosquito Saliva Components
Advances in RNA research have allowed scientists to better study the components of the saliva of “blood-sucking” arthropods and found that the saliva is a complex compound containing a number of proteins and bioactive lipids that have immunomodulatory properties working to undermine the host’s natural defenses against attack.
What Role Does Saliva Play?
The primary role of the saliva the mosquito injects it to circumvent hemostasis, inflammation, and adaptive immunity, all which would initiate the host’s defensive mechanisms and cause the disruption of the feeding.
The saliva proteins accomplish this by widening the blood vessels, inhibiting platelet aggregation, and suppressing the blood from clotting.
It is possible that these proteins adapt as the hosts evolve and adapt.