The widely used insect repellent Deet appears to be losing its
effectiveness against mosquitoes, scientists say. Researchers
from the London School of Hygiene and Tropical Medicine say
mosquitoes are first deterred by the substance, but then later
ignore it. They say more research is needed to find alternatives
to Deet, which was first developed by the US military. The
research was carried out on Aedes aegypti, a species of mosquito
that spreads dengue and yellow fever. The findings are published
in the journal Plos One Dr James Logan, said: "The more we can
understand about how repellents work and how mosquitoes detect
them, the better we can work out ways to get around the problem
when they do become resistant to repellents." Deet - or
N,N-diethyl-meta-toluamide - is one of the most widely used
active ingredients in insect repellents. It was developed by the
US military, following its experience of jungle warfare during
World War II. For many years, it was not clear exactly how the
chemical worked, but rece