Why do mosquito-bites itch?

Do mosquitoes trouble you when you go off to the bed? And give you red itchy bites? Here;s why it happens. A mosquito is a bit like a flying syringe. Its large needle nose, called a proboscis, is ideal for quickly landing on a victim, withdrawing a bit of blood and then taking off for the next target. When a mosquito bites, she(only female mosquitoes bit) leaves behind saliva. In fact, the saliva present in mosquito bites serves the mosquito well, since it works as an anti-coagulant. This means that it helps to keep your blood from clotting long enough for her to take a drink.

When insects like mosquitoes, fleas, or horse flies or even wasps or bees bite you, the same thing happens.