You Smell: Yep, the smellier a person is, the more attractive they are to a mosquito. When a body sweats it produces lactic acid, which is quite tasty to the mosquito. The older the sweat, the sweeter the meal. So you know, take a bath.
Blood Type: Turns out that people with Type O blood are twice as likely to suffer bites as people with Type A blood, according to one study. Also, 85 percent of us secrete a chemical signal that indicates blood type, increasing the chances to get bit since mosquitoes tend to like to know what they are getting.
Bacteria: FeedsGuru reports that the type of bacteria living on our skin varies from person to person. Studies show that people with staphylococcus and variovorax present on their skin will likely suffer more mosquito bites. While other bacteria, such as delftia, tend to keep the pests away.
Carbon Dioxide: Mosquitoes are drawn to the CO2 you exhale, as well. Produce more, get more bug bites. So people who struggle to breathe get bit more. Beer drinkers, for instance, tend to breathe heavier and thus are more prone to bites.