LONDON: British researchers have found chemicals produced by the human body that repel mosquitos, which could lead to a natural, odourless bug spray. Scientists have long known that some people are more tempting targets for mosquitos than others.

But until now it was not clear whether those who were better protected actually produced a natural repellent of their own, or simply produced fewer of the chemicals that attract the insects, said James Logan of Britain's Rothamsted Research centre.

"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 tested people to see how likely they were to attract mosquitos, then collected the chemicals the volunteers' bodies give off - their "liquid body odours", Logan said.

The researchers found certain chemicals were more common in people who were less attractive to the mosquitos. When they sprayed those chemicals on people who normally did attract mosquitos, the insects were 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. So far, 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, Logan said. -Reuters