Insect repellent DEET losing its effectiveness against mosquitoes, study shows

Popular insect repellent DEET is losing its effectiveness against some mosquitoes, a new study shows.

Researchers from the London School of Hygiene and Tropical Medicine studied the effectiveness of DEET, which was developed by the US military in the 1940s, on Aedes aegypti mosquitos that spread dengue and yellow fever.

They found the mosquitoes were initially repelled by the smell of DEET, but later ignored it, the BBC reported.

"We think that the mosquitoes are habituating to the repellent, similar to a phenomenon seen with the human sense of smell,” Dr James Logan was quoted by the Science Daily as saying.

"We found that three hours after pre-exposure the mosquitoes showed behavioral insensitivity, and electroantennography revealed this correlated with the olfactory receptor neurons responding less to DEET," Logan said in the study, which was published in the journal Plos One. 

But Logan doesn’t recommend throwing out your bottles of DEET just yet.

“DEET is a very good repellent, and is still recommended for use in high risk areas. However, we are keeping a close eye on how mosquitoes can overcome the repellent and ways in which we can combat this."

The BBC said the researchers plan to follow up the study by finding out how long the mosquitoes remain insensitive to the chemical after the initial exposure.