Why do some people attract mosquitos more than others?

Most mosquitoes are attracted to the odour of carbon dioxide (C02). All humans exhale C02 with every breath. Yet this fact hardly helps explain why some people are "bitten" more than others.

Three early theories involving gender were proposed and then discarded. First, a theory claimed that women were more likely to be "bitten" than men because mosquitos were supposedly repelled by the strong odour of human sweat. Since the stereotyped view was that men are more likely to wash less often and be sweatier than women, so women received greater mosquito attention.

But this simply wasn't true. Some men are bitten more than some women (and vice versa). Second, a variation of this gender-based theory was that mosquitoes prefer thin-skinned people.

Women generally have thinner skin than men, so women are more likely to be targeted by mosquitoes. But this too proved not to be true. Third, it was theorised that women had some secret hormonal attractant that brought them to the attention of mosquitoes more than men.

Even menstruation and ovulation could be factors in this. But such an attractant was never found. Gender does not now seem to be the all-important factor in mosquito "bite" susceptibility.

One current theory of why mosquitoes "bite" some people more than others is that diet makes one more or less attractive. Dr Randolph Morgan, director of the Insectarium at the Cincinnati Zoo, claimed that regular intake of some materials (such as yeast), which ultimately are exuded through one's pores, changes our smell and has proven effective in deterring mosquito "bites". More recent thinking is that substances in perfumes, soap residues, facial make-up, deodorants, and other compounds on the skin resulted in someone becoming more or less attractive to mosquitoes.

According to the American Mosquito Control Association of Mount Laurel, New Jersey there are over 400 such "magnetic compounds". It appears that some compounds come from within the body and some from without.