DEET is toxic. It is used in mosquito repellents. In two recent CDC publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US, it provided protection similar to repellents containing DEET, (N,N-diethyl meta-toluamide). Until now, DEET was the only repellent recommended by the CDC, and approved for individual use by the Environmental Protection Agency (EPA).
https://mattermore.wordpress.com/2011/05/02/cdc-says-lemon-eucalyptus-as-effective-as-deet/
Tom's Blog on Life and Livingness