Insect repellent ingredient 'is toxic'

The buzz of mosquitoes is one of the less welcome sounds of summer- and of course the pests are linked with the transmission of diseases such as malaria.

But now researchers in France are claiming that a chemical used in most insect repellents could be toxic.

DEET (diethyltoluamide) is the main active ingredient in many repellents. Discovered in 1953, it is effective against a wide range of pests such as mosquitoes. In the past there have been questions raised about the manner in which it works and how it affects insects, as this is not well understood.

The study, reported in the scientific journal BMC Biology, looked at the effects of DEET on both insects and mammals. Vincent Corbel, one of the scientists, says that "We've found that DEET is not simply a behaviour-modifying chemical but also inhibits the activity of a key central nervous system enzyme in both insects and mammals".

They also discovered that the action of DEET on the body is similar to other chemicals often used in combination with DEET in insect repellents. This was considered to be worrying by the researchers as this could increase the toxicity of the mixture.

Corbel continued: "These findings question the safety of DEET, particularly in combination with other chemicals, and they highlight the importance of a multidisciplinary approach to the development of safer insect repellents for use in public health".

It should be noted that these results have not been replicated in humans, with both manufacturers and retailers of insect repellents insisting that they are safe if used according to the instructions.

The researchers say that adults should avoid preparations containing more than 50% DEET and that they should restrict use to no more than 3 times per day. Pregnant woman and children under 6 should avoid the chemical altogether.

This article was published on Wed 5 August 2009