Best mosquito repellent? Catnip may be a better, safer option than DEET and other chemicals

CHICAGO — Tired of getting bitten up by mosquitos in your backyard every summer? Instead of breaking open the wallet for a pest-control service that may provide a smidgen of relief, a new study offers up another suggestion. Try catnip. Yes, catnip. Researchers at Northwestern University report the feline favorite may prove to be a much better — and safer — option to keep insects away.

Of course, the plant used to make catnip, called Nepeta, relaxes a wound up kitty by stimulating a gland that felines have on the roof of their mouth. Cats enchanted by the plant display behavior similar to a female in heat, even if it’s a male. Now, researchers say a chemical within the plant, Nepetalactone, activates a pain receptor in insects called “the wasabi receptor” and keeps them at bay.

A similar receptor exists in humans and is activated by foods like garlic or, as the name suggests, wasabi; but the chemical in catnip only works on insects.

“We discovered that Catnip and its active ingredient Nepetalactone activate the irritant receptor TRPA1, an ancient pain receptor found in animals as diverse as flatworms, fruit flies and humans,” explains Marco Gallio, an associate professor of neurobiology from Northwestern University, in a university release. “We now think Catnip is so aversive to so many insect species because it activates this widespread irritant receptor. What is particularly interesting is that, unlike wasabi or garlic compounds that also activate these receptors in humans, catnip appears to selectively activate the insect receptor. This explains why humans are indifferent to it, and provides a serious advantage for its use as a repellent.”

Why cats are so attracted to catnip is still somewhat of a mystery. However, research suggests it may be because a chemical in the plant interact with the reward system in their brains, much like alcohol and drugs do in humans.

The most commonly used chemical in insect and mosquito repellents, DEET, or diethyltoluamide, was developed for use in jungle warfare in 1944. DEET works by targeting mosquito odor and taste receptors, rendering the insect incapable of recognizing the chemical cues that signal a human prey. But researchers say it could replaced by catnip-based repellents which are easier to get hold of and have a much lower cost than man-made alternatives.

This, they say, could also make it the repellent of choice in developing countries hardest hit but insect-borne diseases. They also believe that, armed with new knowledge of how Nepetalactone works, a new generation of synthetic chemicals could be made with similar properties.

”Mosquitos, in particular those that act as vector for disease, are becoming a bigger problem as climate change creates attractive conditions for them farther north and south of the equator,” says Marcus Stensmyr, co-author and an associate professor at Lund University in Sweden. “Plant-derived compounds represent a new emerging approach to developing insect repellents, as plants have long known how to protect themselves from insect pests.”

The researchers studied a number of insect species to better understand how catnip and its active ingredient work to repel a broad range of insects, while having no irritant effect on humans. To confirm their results, the team ran a range of tests, including offering mosquitoes a blood meal in a dish covered with a nylon sock doused in catnip as well as experiments in which volunteers place their hand in a cage with live mosquitos, with or without the protection of a catnip oil rub.

“This is an entry point to study how this molecule works on the receptor,” says Gallio. “Once we understand its chemistry and how it interacts with the receptor, we could design even more powerful and selectively targeted molecules.”

Their findings are published in the journal Current Biology.

SWNS writer William Janes contributed to this report.

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