Making mosquitoes hate you

New Scientist reports: (edited)

Some unfortunate people are irresistible to mosquitoes, while the scent of some lucky individuals drives the blood-suckers away. Now the specific chemicals have been identified by researchers, who are testing its effectiveness as a natural mosquito repellent.

Everybody produces a mixture of chemicals in their sweat. Some of these, lactic acid for instance, produce a smell which attract biting insects. However, there are also chemicals secreted that mask these scents. Some people have a much higher ratio of 'masking' scents than others, and these are the lucky bastards people who don't get bitten.

What is more, the same benign sweat chemicals that repel the tropical mosquitoes Aedes aegypti – responsible for spreading yellow fever throughout Africa and South America – appear also to disgust the persistent biting midge that terrorises the west coast of Scotland, the researchers discovered.

A Y-shaped chamber was constructed and the scent of different people was channeled into two of the branches by getting volunteers to place their hands at the ends. The blood-sucking insects flew from the thin end of the "Y" towards the human hand they preferred.

The body odour of those individuals found to be unattractive was then collected by sealing their bodies in a foil sack tied under the chin, and collecting and distilling their sweat.

The most potent repellent chemical were then isolated by strapping miniature electrodes to the antennae of female mosquitoes and checking their responses to specific compounds. A key chemical identified as a repellent is a natural, harmless food additive.

The repellent is currently being trialled with 16 volunteers in Africa. Meanwhile, the researchers are testing the repellent against other biting insects, including malaria carrying mosquitoes.
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