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Your next trip to the woods could smell like grapefruit.
The US EPA has approved a citrusy new chemical to fight mosquitoes, ticks, and other biting insects that is natural and nontoxic to people and furry pets.
The name of the chemical is "nootkatone" (NOOT-ka-tone). In nature, you can find it in grapefruit peels and certain Alaskan pine trees. And it is already used in perfumes, colognes, and grapefruit-flavored drinks.
It's more than a repellent. In high enough concentrations, this skin-safe compound can kill mosquitoes, ticks, and other biting pests.
Why Is It Deadly to Pests, Safe for Humans?
Nootkatone is harmless to mammals, but can cause mosquitoes to shake and convulse, dying in less than 15 seconds in some tests. That's because it disrupts a set of chemical transmitters in many insects called octopamine receptors. Mammals lack these receptors.
These receptors respond to octopamine, which works like adrenaline in ticks, mosquitoes, and bed bugs. Too much nootkatone for an invertebrate pest overwhelms their system like an overdose of adrenaline.
Insects actively avoid the smell, which is bright and sweet to people.
Other natural oils have been underwhelming. For example, eucalyptus-like citronella, though used for decades to repel insects, wears off more than four hours faster than DEET, multiple studies show.
The CDC developed nootkatone because it works and lasts as long as DEET on skin—a reason it is popular in colognes and some perfumes.
This is the first new chemical approved by the EPA in 11 years for repelling insects. Scientists have known about the bug-fighting properties of nootkatone for years. Why did it take so long?
To naturally harvest a pound of nootkatone requires more than 180,000 grapefruits. And grapefruit harvests can be disrupted by various natural events, especially hurricanes. This makes natural nootkatone expensive.
Knowing consumers often prefer natural chemicals to artificial ones, the CDC worked with the Swiss biotech company Evolva to develop a proprietary yeast fermentation process for making large batches of this complex molecule at a lower cost, with a lighter ecological footprint than other industrial methods.
Now Evolva has the green light to market "NootkaShield" in a variety of household products.
Although bug sprays are well-known to the public, some scientists are eager to develop a soap that wards off ticks, mosquitoes, and other disease-carrying insects.
Soaps made with nootkatone could serve dual purposes. Before a morning hike they could work to repel insects after being used. Used after a hike, a nootkatone soap could kill persistent pests like ticks while you bathe.
The company says it is "actively pursuing commercial development with all major industries involved in the personal protection against biting insects and ticks."
Products may be ready for the public by 2022, the EPA says.