A US Department of Agriculture (USDA) study has revealed that compounds derived from coconut oil are better at repelling blood sucking insects than diethyltoluamide (DEET), the most common ingredient in most insect repellents.

For over 60 years, DEET was considered the ingredient for insect repellents because of its effectiveness, the USDA said on 31 October. However, growing health concerns and increasing regulations on synthetic repellents had prompted the development of plant-based repellents.

USDA Agricultural Research Service (ARS) scientists had identified specific coconut oil fatty acids that had strong repellency with long-lasting effectiveness against blood sucking insects.

A team of scientists led by Junwei Zhu, with the ARS Agroecosystem Management Research Unit in Lincoln, Newbraska, found that coconut oil compounds were effective for two weeks against biting insects and had a lasting repelling effect on ticks for one week.

Coconut oil alone was not a repellent, stressed Zhu. However, the oil-derived free fatty acid mixture consisting of lauric acid, capric acid and caprylic acid – with their corresponding methyl esters – acted as a strong repellent. This was achieved by encapsulating coconut fatty acids into a starch-based formula, which was revealed in tests to have the ability to provide cattle with protection from stable flies for four days. While DEET was only 50% effective against the stable flies, the coconut oil was 95% effective, the USDA said.

Against bed bugs, the coconut oil compound lasted about two weeks whereas DEET lost its effectiveness after about three days. Coconut oil fatty acids also provided more than 90% repellency against mosquitoes—including Aedes aegypti, the mosquito that transmited the Zika virus.

Zhu said the coconut oil compound offered protection that lasted longer than any other natural repellent.

The USDA said ARS had filed a patent application for the alternative repellent and was working with commercial companies to develop repellent formulas from coconut fatty acids.