Why Some People are Resistant to Mosquitoes?

Smug, aren't they? You might have had the experience of going hiking, fishing, or hunting with companions, one of whom suffers no mosquito bites at all while the rest of you slap and curse. If you weren't lucky enough to have won the genetic lottery, there may be hope yet. Scientists are making progress in identifying the chemical that naturally occurs in some people's sweat, which aids in repelling mosquitoes.

Everybody produces a mixture of odorous chemicals in their sweat which attracts biting insects. Lactic acid, for instance. But the people who do not get bitten also secrete chemicals that appear to mask the scent of the attractive chemicals. This masking can offer a kind of effective camouflage against mosquitoes, according to recent research in the UK at Rothamsted Research in Harpenden and the University of Aberdeen.

These helpful chemicals apparently occur naturally in everybody's sweat, but some people have a much higher ratio than others. Similar to how pheromones work "under our radar" to attract the opposite sex, the body is capable of producing natural mosquito repellent.

The chemicals were found to repel the tropical mosquito species "Aedes Aegypti", which were responsible for spreading yellow fever throughout Africa and South America. It has also been found that the same chemical turns off the dreaded biting midge gnats found along the west coast of Scotland.

The tests were done by placing mosquitoes in a Y-shaped tube and having two human test subjects hold their hands by the filters at either end of the tube's other openings, giving the mosquito a choice to fly towards the person who attracted them the most. Then the sweat of the people who consistently repelled mosquitoes was collected and analyzed.

The sweat samples were then disassembled into their component chemicals and tested on the mosquitoes in the lab one at a time. It turns out that the chemical, whose exact nature must remain confidential until the laboratory receives its patent, is not only naturally occurring but can also be used as a harmless food additive, with the potential to replace the current chemical DEET, which has harmful side effects such as dissolving plastics.

The repellent is currently being tried with sixteen volunteers in Africa. In the meantime, the researchers are testing the repellent against other biting insects, including malaria-carrying mosquitoes. This research was presented at the Royal Society Summer Science Exhibition in London, UK, and has been submitted to a leading peer review journal for publication.

While it is still not known how we might go about manufacturing the chemical for mass production, it is hoped that synthesizing the solution may be possible to lead to a more effective and less destructive mosquito repellent in the near future.