Vincent Corbel from the Institut de Recherche pour le Developpement in Montpellier and Bruno Lapied of the University of Angers, both in France, led a team of researchers that investigated the toxicity of DEET.
"We've found that DEET is not simply a behavior-modifying chemical but also inhibits the activity of a key central nervous system enzyme, acetycholinesterase, in both insects and mammals," Corbel said in a statement.
"These findings question the safety of DEET, particularly in combination with other chemicals, and they highlight the importance of a multidisciplinary approach to the development of safer insect repellents for use in public health."
The researchers said more investigation is needed to confirm or dismiss any potential neurotoxicity of DEET exposure in humans.
The findings are published in the journal BMC Biology.