system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do mosquito bites itch?

Just, why?
gpt
When a mosquito bites you it injects saliva into you which acts as an anticoagulant.  

Without this the mosquito's proboscis would become clogged with clotted blood.  

This saliva is full of proteins which your body recognizes as foreign, kicking off an immune response. Immune cells called Mast cells release (degranulate) histamine.  

Histamine encourages inflammation (why you get a bump) and makes you itch, among other things.  

Some anecdotal  reports indicate that if you apply heat to the bite you can denature the protein and stop the progression of the histamine reaction. You would have to use enough heat to accomplish this, but not enough to burn your skin.