Cinnamon Oil Kills Mosquito Larvae

Better-Smelling Bug Repelling Tests Underway

From the WebMD Archives

July 16, 2004 -- Cinnamon oil is an environmentally friendly way to kill mosquito hatchlings, a Taiwanese study shows.

It might even make bug repelling better smelling -- although whether cinnamon oil keeps adult mosquitoes from biting has yet to be tested.

The findings, from Sen-Sung Cheng, a natural products chemist at National Taiwan University, and colleagues, appear in the July 14 issue of the Journal of Agricultural and Food Chemistry.

Current mosquito-control efforts often rely on organophosphate insecticides. Use of these agents has raised health and environmental concerns, Cheng and colleagues note, so they looked for a different approach. They noted that cinnamon leaf oils have been shown to inhibit bacteria, termites, mites, mildew, and fungi.

Cheng's team derived various oils from the leaves of a type of cinnamon tree that grows in Taiwan. They tested the oils -- and their main ingredients -- against the larvae of Aedes aegypti mosquitoes. This is one of the mosquito species spreading dengue fever -- a viral illness transmitted to humans by mosquitoes during the feeding process.

They found that one chemical in the oil, cinnamaldehyde, worked the best. At less than 50 parts per million, it killed half the mosquito larvae. That's different than DEET, which is currently the best-known mosquito repellent -- meaning it keeps the mosquitos from landing on the skin rather than killing the larvae before they develop.

"We think that cinnamon oil might also affect adult mosquitoes by acting as a repellent," Cheng says in a news release.

Cheng says his team plans to test this theory.

Cinnamon oil -- which has not been tested for use as bug repellent -- is sold in small bottles as an aromatherapy.

According to the National Toxicology program, cinnamaldehyde is used in foods, beverages, medical products, perfumes, cosmetics, soaps, detergents, creams, and lotions. It's also been used as an animal repellent, as an insect attractant, and as an antifungal agent. It may have toxic effects at high concentrations.

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SOURCES: Cheng, S.-S. Journal of Agricultural and Food Chemistry, July 14, 2004; vol 52: pp 4395-4400. News release, American Chemical Society.
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