Why do Mosquito Bites Itch?

During a feeding, the female mosquito bites the human skin, and injects saliva. The saliva contains various proteins that prevent the blood from clotting, as well as proteins that keep the blood flowing into the mosquito’s mouth. Many of the mosquito saliva proteins can cause immune reactions, including allergic reactions. Typically, however, most people have a variety of reactions to mosquito bites, and the symptoms change over time, depending on the amount of bites a person received. These reactions can include both immediate and delayed swelling and itching around the bite area.