Mosquitoes get used to the smell of one of the most common active ingredients in insect repellent and are less sensitive to it after three hours of exposure, according to a British study published yesterday.
The researchers briefly exposed mosquitoes to Diethyl-meta-toluamideon a human arm and then tempted the insects to the same DEET-covered arm again a few hours later.
They found mosquitoes that had previously been repelled by DEET were able to ignore the smell the second time and landed on the arm significantly more, although still not as much as on an arm without repellent.
The research was done on Aedes aegypti mosquitoes, which are found in Queensland and throughout South East Asia, including Indonesia, and are the main insect responsible for the spread of dengue fever.
Paper author James Logan, from the London School of Hygiene and Tropical Medicine, said the results did not mean people should stop using insect repellents.
"DEET is a very good repellent and is still recommended for use in high-risk areas," he said.
WA Health Department managing scientist of environmental health hazards Michael Lindsay said although cases of mosquito-borne diseases were down this summer it was still important for people to protect themselves against bites.