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Sweetgrass as Mosquito Repellent: Research Catches Up to Native Knowledge

Western science has caught up to Native knowledge when it comes to sweetgrass being used as bug repellent—researchers have IDed the chemicals at play.
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Using sweetgrass to keep the mosquitos away is nothing new to Native Americans. The fragrant, sacred plant also plays an important part in Native ceremonies and is often used in sweat lodges. According to Native Naturals, who sell sweetgrass oil, and make products out of sweetgrass, it is also often burned after sage to purify and encourage positive vibrations or spirits to enter.

“[Sweetgrass] gives off a sweet aroma that repels mosquitoes,” Charles Cantrell, Ph.D., said in a press release regarding researchers findings.

So, how did Western science catch up? Researchers at the U.S. Department of Agriculture in collaboration with researchers at the University of Guelph and the University of Mississippi discovered the two chemicals in sweetgrass that repel mosquitos: phytol and coumarin.

Coumarin is already in some commercial anti-mosquito products, but phytol has so far only been reported to have repellent qualities in scientific literature.

After extracting sweetgrass oil, the researchers filled vials with a feeding solution that mimicked human blood and covered the vials with a thin membrane. The membranes were coated with different substances, and the mosquitos could either bite the membrane to get to the “blood” or pass it by.

“Then you take the mosquitoes and squish them on some paper,” Cantrell said in the release. “If they have the blood mimic in them, you see it right there on the paper.”

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A mosquito seen close-up and at high magnification. The pests are known to spread diseases such as malaria and West Nile virus.

Of all the substances, the sweetgrass oil got the fewest bites, meaning it matches the repelling power of DEET, the most popular bug repellent.

Cantrell is happy to have demonstrated that “we were able to find constituents that are known to act as insect repellents in a folk remedy, and now we understand that there’s a real scientific basis to this folklore.”

The researchers will be presenting their findings at the 250th National Meeting & Exposition of the American Chemical Society through Thursday, August 20.

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