Question: Heya, im ellen, i was wondering, why do misquoto bites itch?

Steven Gardner answered on 20 Jun 2013:

That’s a good question, so I looked up the answer.

When a mosquito bites you it injects you with a small amount of saliva. This saliva has inside it a chemical to stop your blood from clotting (the general term is an anticoagulant). When the mosquito flies away it leaves some saliva behind, the body recognises this and the immune system kicks in. It releases antibodies and then a hormone called histamine. Histamine makes your capillaries (the tiny blood vessels) bigger to allow white blood cells to travel down them and fight infections. Unfortunately this also causes swelling and inflammation, which is what itches. Histamine is also what you produce during hayfever, which is why you take antihistamine tablets to combat it (Not that they ever seem to work for me!)