Mosquitoes generally prefer blood type O over other blood types. Research indicates that mosquitoes are more attracted to people with blood type O, possibly due to specific proteins or antigens in the blood. Studies have shown mosquitoes landing more frequently on type O individuals compared to types A, B, or AB. People with type A blood tend to attract mosquitoes the least. However, blood type is just one of several factors influencing mosquito preference, which also includes body odor, carbon dioxide, heat, and other chemical signals from the body.

Some specific findings include:

• A 2019 study found mosquitoes chose type O blood feeders over other types.
• A 2004 study showed mosquitoes landed almost twice as often on people with type O blood than type A.
• Mosquitoes may also be attracted to type O secretors who secrete certain antigens in body fluids.

Other factors, such as body odor and skin microbiota, are also important in mosquito attraction, but among blood types, type O is the most favored by mosquitoes.