A topical 
insect repellent with extended duration of protection was obtained from mixtures of molecules based on two or more volatile repellent organic molecular species occurring naturally on the 
human skin surface. The novel repellent comprises mixtures of lower, intermediate, and higher volatility 
organic molecules. Active ingredients for formulations are obtained from homologous series of carboxylic acids, alcohols, ketones, and lactones which span a similar range of volatility and which occur naturally on the 
skin surface. Volatile 
silicone fluid imparts mildness and water repellency to the repellent formulations. The new natural repellent exhibits the 
longevity and repellency that is comparable to N,N-diethyl-m-toluamide (
DEET), a synthetic compound employed in almost all commercial formulations, but the inventive natural repellent is more acceptable than 
DEET, which has an unpleasant 
odor and imparts a greasy feel to the 
skin. The inventive 
insect repellent, formulated in a volatile 
silicone fluid, was shown to repel and incapacitate stable flies. This finding demonstrated that repellency was not limited to mosquitoes, but extends to other 
biting flies or insects, thus demonstrating the utility of the novel 
insect repellent for protecting pets and 
livestock as well as humans.