Mosquitoes giving DEET the brush-off

The insect repellent Deet appears to be losing its effectiveness against mosquitoes, scientists say. Researchers in a PLOS One study say mosquitoes are first deterred by the substance, but then later ignore it. They say more research is needed to find alternatives to Deet - or N,N-diethyl-meta-toluamide - which is one of the most widely used active ingredients in insect repellents.