Ever notice how mosquitoes seem to frantically feast on some folks while ignoring others? It’s not just your imagination, says entomologist Joseph M. Conlon, a technical advisor to the American Mosquito Control Association. “There is no question that some individuals are more attractive to mosquitoes due to chemicals they secrete from their skin and from their particular skin flora.” We talked with experts to learn more about the biological factors that can turn a person into skeeter bait. If the little buggers happen to find you irresistible, here are five possible reasons why:

You’re pregnant

Female mosquitoes (the kind that bite) have a thing for carbon dioxide. Special nerve receptors help them detect the gas in the environment. What does that have to do with your baby bump? A 2002 study published in The Lancet found that women in the later stages of pregnancy (with a mean gestational age of 28 weeks) exhale 21% more CO2 than their non-pregnant peers. The researchers speculated that this physiological difference could help explain why the pregnant women who participated in their experiments attracted twice as many mosquitoes. (Because itchy welts are just what you need in your third trimester.) But CO2 may not be the only reason you’re suddenly more appealing: It could also be that pregnant women emit volatile odors that draw the insects, says Laura Harrington, PhD, a professor in the department of entomology at Cornell University.

You’re dripping with sweat

If bug bites drive you nuts, you may want to take your workouts indoors this summer. Lactic acid, a byproduct of vigorous physical activity that’s excreted through sweat, is “indeed an attractant” for mosquitoes, according to Conlon. If you’re sweating profusely, your higher body temperature may play a role too. Warmth becomes more attractive as mosquitoes approach a potential host, says Conlon.

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