Actually, Jim, mossies are attracted to carbon dioxide that people and animals exhale. I read that in some scientific article once.
From personal experience, I have observed that they are attracted to some people more than others. I was hiking with a friend once, and the mosquitoes were driving him nuts, with a dozen stuck to his shirt and more buzzing his face. Meanwhile, I was not being bothered much at all.
I like to take him along on all my hikes.