system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why doesn't it hurt to scratch mosquito bites until I bleed?

It shouldn't feel like ecstasy to scratch at my skin until it breaks. What is going on?
gpt
Mosquitoes inject a local anesthetic when they bite to keep their meal from detecting their presence. The actual act of them sucking your blood is not painful due to this. However, their saliva does cause an allergic reaction at the site of the bite. Your body produces an localized histamine reaction to fight against the saliva. The histamine response causes you to become itchy at the spot, which at the same time is anesthetized.