Everyone who has ever been camping or walking in the wild with friends can’t have failed to notice how insects seem to prefer some people’s flesh to others. Some unlucky souls are totally covered in itchy red blotches and others are miraculously spared. Sometimes only some family members are affected. My mother has never been bitten by a mosquito (though fleas like her) while my brother and I are often the targets.
Previous observations have shown a higher mosquito preference for larger people (who produce more CO2), beer drinkers and pregnant women, and although diet was often suspected as a factor, nothing in what we eat (even garlic) stood up to scrutiny.
The authors of a new study in PLOS One claim to have found the answer. They studied the differences in attraction of skin odours to mosquitoes, specifically Aedes aegypti, in a group of brave volunteers drawn from a group of female identical and non-identical twins – part of the large national TwinsUK cohort that I set up 21 years ago. The reason for using both kinds of twin was to separate the effects of nature and nurture (or genes and environment). In humans this is the only way to get a good estimate of the contribution of genetics to the differences between people.
Aedes aegypti during blood meal James Gathany/USDHHS