Compounds derived from coconut oil are better than DEET at repelling blood-sucking insects, a new U.S. Department of Agriculture (USDA) study finds.
Using repellents is one of the most efficient ways to prevent disease transmission and discomfort associated with insect bites. For more than 60 years, DEET(N,N-Diethyl-meta-toluamide) has been considered the gold standard in insect repellents — the most effective and long-lasting available commercially.
However, increasing regulations and growing public health concerns about synthetic repellents and insecticides like DEET have sparked interest in developing plant-based repellents that are more effective and longer lasting. Now, USDA’s Agricultural Research Service (ARS) scientists have identified specific coconut oil fatty acids that have strong repellency and long-lasting effectiveness against multiple insects — mosquitoes, ticks, biting flies and bed bugs — that can transmit diseases to humans and animals.
Coconut Oil Compounds
A team of scientists led by entomologist Junwei (Jerry) Zhu, with the ARS Agroecosystem Management Research Unit in Lincoln, Nebraska, found that the coconut oil compounds were effective against biting flies and bed bugs for two weeks and had lasting repellency against ticks for at least one week in laboratory tests.
In addition, the compound showed strong repellency against mosquitoes when higher concentrations of coconut oil compounds were topically applied.
Some people refuse to use DEET and turn to folk remedies or plant-based repellents. Most currently available plant-based repellents work for only a short period, Zhu noted.
Coconut oil itself is not a repellent, Zhu emphasized. However, the coconut oil-derived free fatty acid mixture — lauric acid, capric acid and caprylic acid as well as their corresponding methyl esters — provides strong repellency against blood-sucking insects.
By encapsulating coconut fatty acids into a starch-based formula, field trials showed this all-natural formula could provide protection to cattle against stable flies for up to 96 hours or 4 days.
DEET was only 50 percent effective against stable flies, while the coconut oil compound was more than 95 percent effective.
Against bed bugs and ticks, DEET lost its effectiveness after about three days, while the coconut oil compound lasted for about two weeks. Coconut oil fatty acids also provided more than 90 percent repellency against mosquitoes — including Aedes aegypti, the mosquito that can transmit the Zika virus.
These coconut oil-derived compounds offer longer-lasting protection than any other known natural repellent against insect blood-feeding, according to Zhu.
DEET, developed in 1944, is considered by many as the gold standard of insect repellents. It was first used by the military during World War II, and subsequently commercialized in 1957.
Although DEET has been the most extensively used personal arthropod repellent for over six decades, it has been frequently associated with human health issues, particularly for infants and pregnant women.
Junwei J. Zhu, Steven C. Cermak, James A. Kenar, Gary Brewer, Kenneth F. Haynes, Dave Boxler, Paul D. Baker, Desen Wang, Changlu Wang, Andrew Y. Li, Rui-de Xue, Yuan Shen, Fei Wang, Natasha M. Agramonte, Ulrich R. Bernier, Jaires G. de Oliveira Filho, Ligia M. F. Borges, Kristina Friesen & David B. Taylor
Better than DEET Repellent Compounds Derived from Coconut Oil
Scientific Reports volume 8, Article number: 14053 (2018)
Image: Егор Камелев/Unsplash