The Secret Behind New Insect Repellent’s Potent Punch Is Found in Grapefruit

The EPA just approved nootkatone, a chemical found in grapefruit and cedars that kills and repels ticks, mosquitoes and other insects

A stock image of a basket of grapefruit, a grapefruit sliced in half sits in the foreground
Hopefully the new repellents will smell better too! Tom Kelley / Contributor

A citrusy smelling oil found in cedar trees and grapefruits repels and kills ticks, mosquitoes and a wide variety of other pests, reports Donald G. McNeil Jr. of the New York Times. The naturally occurring chemical, called nootkatone, is responsible for the distinctive odor and taste of grapefruit, and it's widely used in the fragrance and food industries.

“If you drink Fresca or Squirt, you’ve drunk nootkatone,” Ben Beard, deputy director of vector-borne diseases at the Centers for Disease Control and Prevention (CDC), tells the Times.

A statement from the Environmental Protection Agency (EPA) announced on Monday that the agency has approved the substance and considers it non-toxic to people and animals. This guidance means companies can now use the ingredient to create new products for use on humans or animals, reports Akshay Syal of NBC News. Consumer products would still require review by the EPA but could be available as early as 2022.

Beard tells the Times that the mechanics of how nootkatone works are “not known in great detail.” Beard says the compound appears to stimulate receptors involved in sending electrical impulses between the insect’s nerve cells. In large enough doses, the insects essentially “twitch to death,” per the Times.

The statement indicates that nootkatone may be just as effective as existing insect repellents, but may be longer lasting. Researchers working for the CDC discovered nootkatone’s properties and developed it into a repellent and insecticide in collaboration with biotech company Evolva.

Joel R. Coats, an insect toxicologist at Iowa State University, tells the Times his own research found nootkatone to be “an impressive repellent but a weak insecticide.” Coats adds that the new chemical provides protection for several hours, outlasting other plant-based repellents. It's even better at discouraging ticks than DEET, picaridin or IR3535, and just as good at repelling mosquitoes.

Nootkatone is the first new insect repellent compound to be introduced since 2009, per NBC News. It may even shoo away fiendish critters that have developed a resistance to the existing arsenal of repellents and insecticides.

The grapefruit-scented compound works differently from other insecticides and can kill insects that are resistant to pyrethroids and other common insecticides, according to a statement from the CDC.

That resistance is a problem because of the deadly illnesses that mosquitoes, ticks and fleas can carry, including malaria, Lyme disease, West Nile and Zika. The Times quotes a 2018 CDC report indicating that the incidence of these tick, mosquito and flea-borne diseases has tripled in the United States over the last 15 years.

“I think it's a major contribution to our arsenal of repellents,” Brian Fallon, director of the Lyme and Tick-Borne Diseases Research Center at Columbia University, tells NBC News.

Manuel F. Lluberas, a public health entomologist who has worked on numerous mosquito-control campaigns, tells the Times he hopes the new ingredient would find favor among people who are reluctant to use synthetic repellents, adding that it will be most impactful if it can be made cheaply enough to be purchased by foreign aid programs.

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