Mosquito bites are the ultimate temptation—the little red welts are just itching (get it?) to be scratched. When you finally give in, scratching feels oh so sweet. That's because the process releases dopamine and drowns out the itchy sensation, though it doesn't necessarily get rid of it.
This itch-scratch cycle isn't a big deal for most of us (though we bet you're feeling itchy just reading this story), but it can become a real problem if you have eczema, psoriasis, or a similar disorder.
why we itch to help chronic scratchers find relief. For now, from HowStuffWorks does a good job explaining the theories being tested.