Why are mosquitoes drawn to certain people more than others?

Many factors that determine mosquito-feeding behavior are still not understood. However, these factors seem clear: Female mosquitoes use carbon dioxide as a primary cue to a person’s location. A host-seeking mosquito is guided to its skin by following the carbon dioxide emitted when a host exhales. Once they’ve landed, a number of short-range attractants are used by the mosquito to determine if the host can provide an acceptable blood meal. Folic acid appears to be important in making this determination.