system
Given the following post, respond as if you're commenting on Reddit:
human
Why do mosquito bites itch?
gpt
When a mosquito 'bites' you [it's not really a bite], this is what happens.

She [it is always a she, they only do it to feed their eggs and not to nourish themselves] first injects you with an anticoagulant so the blood will flow without clotting.

After getting their blood, most of the anticoagulant is then sucked back up with the blood.
And this stuff is what makes you itch.

So, if you smack the mosquito while it is still sucking, it will itch a lot more than if you let them take the blood, a miniscule amount, and suck back the stuff that makes you itch.