One of the biggest annoyance in the world is the nuisance caused by the smallest insects, specifically mosquito bites. Itching around the red bump area after the bite is much more irritating. So what mosquito is doing to our body in that split second?
First of all, itching is not caused by just the bite itself. It is the result of reaction of the human body's immune system to certain protein in mosquito's saliva.
Mosquito uses saliva to suck as much as blood from the human body. Its mouth part is made up of multiple tubes where it uses one tube to suck the blood and another to pump saliva into the blood vessel.
The saliva acts as an anticoagulant, which prevents blood from clotting. Hence there won't be any disruption in the blood flow.
Even though the saliva is harmless, human immune system is hypersensitive when it senses a foreign body. It reacts to this condition by releasing histamine.
Histamine is a biological substance that calls for White blood cells, blood plasma proteins to the site of injury for fighting with the foreign body(saliva).
The allergic reaction of histamine to some protein in the mosquito saliva causes itching and red inflammation.
The red bump usually clears up on its own in some time. But sometimes mosquito bite causes large swelling and redness. This kind of reaction is called Skeeter syndrome which normally occurs in children.
Mosquito saliva is harmless but sometimes it acts as a carrier for viruses like Malaria, Zika, etc.