Mosquitoes are attracted to bacteria and microbes that live on skin. They are also attracted to chemicals emitted through the skin, such as ammonia and octenol, which is a component of sweat.
Additionally, mosquitoes are drawn to carbon dioxide, movement and heat, factors that put pregnant women at greater risk of mosquito bites. The insects seek out people who emit higher concentrations of steroids, cholesterol, uric acid, lactic acid and other chemicals to which the mosquitoes are attracted. Much of these emissions are genetically determined, with 85 percent of susceptibility to mosquito bites traceable to genetics. Certain medications, such as steroids, can seep through the skin and attract mosquitoes.
Dark clothing allows mosquitoes to spot victims more easily.