I'm a sweaty dude and I'm also O-. I very rarely ever notice mosquitoes around and maybe contend with 2-3 bites a year. My wife is an A type, who doesn't sweat profusely, but she is harassed by mosquitoes every year. She gets it really bad, to the point where we're both actively trying to defend her against them with sprays and portable fans when we're out hiking or backpacking, etc...