It has been a question that has long perplexed people: why are some individuals seemingly immune to mosquito bites, while others suffer endless attacks?
Scientists at Rothamsted Research in the U.K. have made progress in identifying which of the approximately 300-400 chemical odors produced by the human body attracts or repels insects (insects have very keen sense of smell they use to guide them to their prey).
Using two groups of test subjects, one ‘attractive’ to mosquitoes and one ‘unattractive, the scientists were able to isolate and identify 7-8 distinct chemical odors which repelled mosquitoes. Some of these odors were thought to be related to stress.
Dr. Logan and his team have found only a small number of body chemicals—seven or eight—that were present in significantly different quantities between those people who were attractive to mosquitoes and those who weren’t. They then put their findings to the test. For this they used a so-called Y-tube olfactometer that allows mosquitoes to make a choice and fly toward or away from an individual’s hand. After applying the chemicals thought to be repellant on the hands of individuals known to be attractive, Dr. Logan found that the bugs either flew in the opposite direction or weren’t motivated by the person’s smell to fly at all.
The group’s latest paper, published in March in the Journal of Medical Entomology, identified two compounds with “significant repellency.” One of the compounds, 6-methyl-5-hepten-2-one, is a skin-derived compound that has the odor of toned-down nail-polish remover, according to George Preti, an organic chemist at the Monell Chemical Senses Center in Philadelphia, who is involved in a separate line of research into insect-biting behavior. The other, identified in the paper as geranylacetone, has a pleasant odor, though there is some question about whether the chemical is formed by the human biochemical process or is picked up in the environment, Dr. Preti says.
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