Some people seem to get bitten by mosquitoes far more than others, and it’s not just bad luck. Scientists have found that certain factors, including blood type, body chemistry, and even the amount of carbon dioxide you exhale, can make you more attractive to these insects.

From genetics to body heat, a variety of hidden traits influence how likely you are to be targeted. Understanding what draws mosquitoes in can help explain why they seem to prefer certain people, and what you can do to avoid those itchy bites.