New repellents keep mosquitoes away

The strong chemical smell of your mosquito spray may soon be a distant memory, following the discovery of new repellents that are three times more effective at keeping insects at bay, but also smell nicer and do not make your skin sticky.

Most mosquito repellents today use an active ingredient called DEET, which has been in use for the past 50 years and has a strong chemical smell. It is effective in keeping insects away but is unpleasant to wear.

Keeping mosquitoes away can be a matter of life and death in some climates, as the bite of the bloodsucking mosquito female can transmit malaria and encephalitis, among other conditions.

To discover new repellents, researchers used a computer model that looked at the molecular structures of more than 30,000 chemical compounds that had in the past been tested as repellents.

The computer software looked at the structural features of a chemical that would make it effective against insects and then trained it by looking at the molecular structures of 150 effective repellents. Using this information, the software on its own devised the chemical traits of an effective repellent.

Ultimately the researchers synthesized 23 new compounds, 10 of which gave 40 days protection against mosquitoes, as compared to 17.5 days for DEET. This long lasting protection took place when a cloth soaked with the new repellent was worn by a volunteer. When applied to the skin, the effectiveness of the repellent is reduced to several hours.

The results of the study, led by Ulrich Bernier, were presented yesterday at the National Meeting of the American Chemical Society.

The new repellents will now be extensively tested in the market and go through an approval process, which may take years.

This article was published on Mon 17 August 2009