Friday, July 18, 2014

Some odors we emit make us more attractive to mosquitoes; various repellents, including plant oils, are available

Mosquitoes are attracted to some people more than others because of skin odors or chemicals they emit, Jill Richardson writes for Salon. Carbon dioxide, heat, moisture, scent and appearance attract mosquitoes, but it's the chemicals you emit that make them want to take a bite, she writes.

Photo from Lexington Herald-Leader
Kentucky has about 60 of the 150 species of mosquitoes found in the U.S., according to the University of Kentucky Public Health Entomology Laboratory. Not all bite, and if one does, it is always a female, which needs the protein found in blood to make her eggs, UK extension entomologist Lee Townsend writes in The Courier-Journal.

Each species differs in biting persistence, habits and ability to transmit disease and even flying ability, Richardson writes, but it is the chemicals we emit that dictate their preference of who to bite.  L-lactic acid, ammonia, carboxylic acids and octenol, especially in combination with each other, are the chemicals most likely to attract them.

Scientist have found that adding l-lactic acid to the scent of someone who is not normally bitten by mosquitoes will make them more attractive to certain kinds of mosquitoes, Richardson reports. The presence of carbon dioxide has also been found in studies to be attractive to certain mosquitoes. Ammonia, which occurs from a pH change when bacteria in sweat multiply, is also appealing to mosquitoes.

So are smelly feet. Studies with Limburger cheese, which resembles human foot odor, have confirmed this. However, malarial mosquitoes are most attracted to this odor, so the saying that "If you keep your feet clean then mosquitoes won't bite," is good advice only if you are traveling in the tropics, Richardson writes.

Human odor that attracts mosquitoes may be genetically driven, but theories vary. One says individuals who are not attractive to mosquitoes don't produce the odors that attract them; and another says some people actually emit an inherited odor that keeps mosquitoes from finding them.

For those who consider themselves "mosquito bait," Richardson makes several suggestions: bathe at dusk, when mosquitoes come out, to minimize sweat odor, rub your body with antimicrobial plants like sage, wear a full-body mosquito net suit or use a repellent, which is the most convenienct, effective protection.

The most common repellent is DEET, available over the counter in many preparations. A prescription repellent is permethrin, which Richardson says may be carcinogenic though it is approved by the Environmental Protection Agency.

A young jewelweed plant
Many people use essential plant oils, though they evaporate quickly, requiring frequent application. The one most commonly recommended is lemon eucalyptus oil, which has proven effective. Richardson's article has details about other plant oils, and recommends crushed jewelweed as a remedy for mosquito bites.

Darla Carter of The Courier-Journal also had a good roundup of mosquito information in the Louisville paper's July 18 edition:

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