The EPA approved a citrus oil, safe enough to ingest, that both repels and kills ticks and mosquitos.

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The EPA approved a citrus oil, safe enough to ingest, that both repels and kills ticks and mosquitos.

A new weapon has been added to the fight against insect-borne illnesses including Lyme disease and malaria.

According to a 2018 report by the Centers for Disease Control and Prevention, diseases caused by the bites of ticks, mosquitoes and fleas have tripled in the United States in the last 15 years. They include Lyme disease, anaplasmosis and Rocky Mountain spotted fever from ticks; West Nile, dengue, Zika and chikungunya from mosquitoes; and plague from fleas. In tropical countries, malaria and yellow fever are major killers and elephantiasis is also spread by mosquitoes. Lethal Crimean-Congo hemorrhagic fever is spread by ticks and kala azar is spread by sandflies.

Well, there's now a new weapon in the fight against insect borne pathogens. The chemical repels mosquitoes, ticks, bedbugs and fleas — and, in high concentrations, kills them, according to the C.D.C. It may also be effective against lice, sandflies, midges and other pests, some of which can carry lethal diseases. It repels ticks even better than synthetics like DEET, picaridin or IR3535 do. Unlike citronella, peppermint oil, lemongrass oil and other repellents based on plant oils, nootkatone does not lose its potency after about an hour, but lasts as long as the synthetics.

It is not oily, lasts for hours and has a pleasant grapefruit-like scent, said Ben Beard, deputy director of the division of vector-borne diseases at the C.D.C., naming two grapefruit-flavored sodas.

“If you drink Fresca or Squirt, you’ve drunk nootkatone,” Dr. Beard said.

The Environmental Protection Agency approved the new chemical that both repels and kills ticks and mosquitoes. The chemical, nootkatone, is found in citrus fruit and cedar trees and has been used in food and in perfumes for years. The chemical is nontoxic to mammals. The goal is to create a compound that would appeal to people that would reject a synthetic repellent and can be manufactured cheaply enough to be purchased in bulk to help underserved populations.

“Its use as an insecticidal soap has great potential,” said Duane J. Gubler, a former C.D.C. chief of vector-borne diseases.

“Most plant terpenes will kill bugs if you go to a high enough dose but I haven’t seen any data that supports using it as an insecticide,” Joel R. Coats, a specialist in insect toxicology at Iowa State University, using a term for aromatic oils exuded by many plants to repel invasive insects. “I’ve seen lots of data on it as a repellent.”

It is “not known in great detail” how nootkatone works, Dr. Beard said, but it appears to activate octopamine receptors, which in insects send electrical impulses from one nerve cell to the next. Unable to turn off the signal, the bugs twitch to death.

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