Demonstrated by lab tests, mosquitoes now develop resistance to substances used in repellents, according to researchers at the Swedish University of Agricultural Sciences (SKU).

In particular, the notorious yellow fever mosquito resists the repellent DEET, a substance used worldwide. Photo receptors in the mosquito's antennae seem to have stopped responding to DEET, possibly because the protein binds to the DEET has mutated. Mosquitoes' ability to develop resistance has been proven to become hereditary.

"We have found that yellow fever mosquitoes no longer feel the smell of DEET and are thus not rejected by it. This is because a certain type of sensory cells in the mosquito's antennae are no longer active," says Richard Ignell, researcher at the Department of Chemical Ecology at SLU in Alnarp.

Stressing the need for additional studies, researchers are advising caution in the use of DEET and other mosquito repellents on larger scales in limited areas in order to prevent other mosquito species from developing immunity.