Multiple factors influence a person's probability of being bitten by mosquitoes.
First, blood type—people with type O blood are about 83% more likely to be bitten than those with type A, with type B falling in between.
Second, skin microbiome composition—everyone has a unique bacterial community on their skin surface; certain bacterial metabolites of sweat produce volatile compounds that are more attractive to mosquitoes.
Third, carbon dioxide output—larger individuals and pregnant women exhale more CO2.
Pregnant women are bitten about twice as often as non-pregnant women.
Fourth, body temperature—individuals with a slightly higher body temperature produce a stronger infrared heat signature for mosquitoes.
Fifth, exercise and sweating—after exercise, the concentration of lactic acid, uric acid, and ammonia on the skin surface rises, all of which are mosquito attractants.
Sixth, alcohol consumption—studies have shown that drinking a single bottle of beer can temporarily increase a person's attractiveness to mosquitoes.
Seventh, clothing color—mosquitoes more easily spot dark-colored targets than light-colored ones.
Overall, the most effective ways to reduce your mosquito appeal are to wear light-colored, long-sleeved clothing, use a DEET-based repellent, and stay indoors during peak mosquito activity hours.