From Reuters via the ABC :
British researchers have found chemicals produced by the human body that repel mosquitos, which could lead to a natural, odourless bug spray.When I first came to Oz, I was plagued by mozzies. But after a few years, I had no more problems than the locals. I've noticed the same phenomenon with visitors from overseas, the Mozzies make a, well, bee-line for them. Based on those observations, it may be that it's something that gets triggered by being bitten.
Scientists have long known that some people are more tempting targets for mosquitos than others.
James Logan, of Britain's Rothamsted Research centre, says until now it has not been clear whether those who are better protected actually produce a natural repellent of their own, or simply produced fewer of the chemicals that attract the insects.
"Other research groups have assumed that people who were unattractive (to mosquitos) might just lack attractive chemicals," he said.
"But we've come at it from a different point of view and suggested that they may have chemicals that make them less attractive."
His team has tested people to see how likely they were to attract mosquitos, then collected the chemicals the volunteers' bodies give off - their "liquid body odours".
The researchers have found certain chemicals are more common in people who are less attractive to the mosquitos.
When they spray those chemicals on people who normally do attract mosquitos, the insects are no longer interested.
"It basically masks the attractive chemicals. This chemical is telling the mosquito that there's nothing there," he said.
"I'm not saying it's one chemical. We've got several chemicals. It's likely to have something to do with different ratios of chemicals."
Best of all, the natural bug repellent is not detectible by human noses, so it would have no smell.
Mr Logan says the team is keeping its recipe secret because it wants to market what could be a new natural bug repellent that has no odour detectible by humans.
Assuming the Aquatic Ape Theory is correct, (and I'm persuaded that it is, BTW), then mosquitos would have been a problem for Homo Sap's ancestors, since coastal areas and riverine estuaries are a haven for them. Having a natural insect repellent not found in the other two (non-aquatic) species of chimpanzee would be a plausible evolutionary adaptation. Obvious - in hindsight.