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Which Mosquito Repellents Work?

People spend a lot of effort trying to repel mosquitos  - because the bites are so annoying and because they spread serious diseases. New research looking at different mosquito repellents - both DEET and non-Deet ("natural") products - had interesting results. What was once thought effective in repelling mosquitoes doesn't work at all (vitamin B patch), and what was thought attractive to mosquitoes may actually repel them (floral scents), and the "natural" alternatives may or may not work. Also - the species of mosquito is important (they tested Aedes aegypti and Aedes albopictus), for they found that there was some variation among the 2 species in what they were attracted to or repelled by. Best choices for protection lasting at least 2 hours: DEET repellants, Cutter lemon eucalyptus insect repellent, and Victoria's Secret Bombshell. Best protection lasting 4 hours: DEET repellants, and Cutter lemon eucalyptus insect repellent. This last non-DEET product contained lemon-eucalyptus oil containing p-menthane-3,8-diol. Of course there was an untreated control (an attractive to mosquitoes volunteer's bare hand) in the study for comparison purposes.

However, while EcoSmart organic insect repellent  worked for 4 hours for Ae. albopictus mosquitoes, it only worked for the first few minutes for Ae. aegypti mosquitoes (so don't buy this product)For years people thought that Avon Skin So Soft worked well as a repellent - well, forget it- not good at all. Other products that did not work: a mosquito skin patch (vitamin B), and Cutter natural insect repellent. These results showed that DEET-free products containing citronella or geraniol did not work. See the original study for the result lists for 10 products for both species of mosquitoes. From Popular Science:

VICTORIA’S SECRET PERFUME WARDS OFF MOSQUITOES, STUDY FINDS

Because mosquitoes carry diseases like malaria and dengue fever, and irritate us, humans do a lot to avoid them. In most places people have to fend for themselves against the pests by sleeping under mosquito nets or using repellant. A number of new repellant formulas have hit the market in recent years, many with questionable efficacy. Researchers at New Mexico State University decided to compare the effectiveness of different repellants and perfumes, according to a study published recently in the Journal of Insect Science.

The Y-shaped tube used in the study.  Rodriguez et al, Journal of Insect Science, 2015

The researchers tested eight commercially available repellents, two fragrances, and a vitamin B patch that reportedly keeps the mosquitoes at bay, on two different species of disease-carrying mosquitoes. To test the efficacy of each, the researchers put a mosquito at the long end of a Y-shaped plastic tube. One of the researchers who is particularly attractive to mosquitoes placed her two hands at the ends of both forked tubes—one hand was untreated, the other treated with the chemical being tested. If the mosquito avoided the tube with the treated hand by staying still or moving towards the untreated hand, the researchers determined that the repellent worked.

The researchers found that, among repellents, those that contained the tried-and-true ingredient DEET were most effective in warding off the mosquitoes. A few others, such as Cutter Lemon Eucalyptus Insect Repellent, worked almost as well, while most of them (including the vitamin patch) didn’t make any difference.

While those findings weren’t unexpected, the researchers were surprised to find that Avon Skin So Soft Bath Oil repelled the mosquitoes for about two hours. Another fragrance, Victoria’s Secret Bombshell perfume, also repelled the mosquitoes and lasted even longer.

That overturned the previous understanding about how mosquitoes interpret scents. “There was some previous literature that said fruity, floral scents attracted mosquitoes, and to not wear those,” said Stacy Rodriguez, a research assistant involved in the study, said in a statement. “It was interesting to see that the mosquitoes weren’t actually attracted to the person that was wearing the Victoria’s Secret perfume – they were repelled by it.”

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