Study compares insect repellents and rates their effectiveness

The Zika virus has made many people more aware of the need to wear repellents. Consumer Reports tested several DEET-based and natural repellents and recommended several brands in their April issue. In addition, in 2015, a group of researchers from New Mexico State University also tested several DEET-based and natural repellants, along with a bath oil, one perfume and a skin patch to compare a more varied group of products.

The peer-reviewed article, which appeared in the Journal of Insect Science in 2015, compared ten “repellents” to a control. Three DEET-based products were tested, including the popular OFF Deep Woods repellent, in addition to four natural repellents, two fragrances and a mosquito skin patch containing Thiamin B1.

One of the authors provided her hands as the bloodmeal for the mosquitoes; one of her hands was covered in each repellent and the other hand was uncovered to act as the control. Twenty mosquitoes were released into the vial for each repellent. Mosquitoes were counted as attracted to something if they flew into the tube for either the control or repellent.

The authors tested the repellents on Aedes aegypti and Aedes albopictus, separately. Overall, tests showed that Ae. albopictus was not as attracted to the control hand as was Ae. aegypti.

On the other hand (literally), entomologist Stacy Rodriguez and her fellow researchers compared the effectiveness of the following chemistries:

  • Repel 100 insect repellent
  • OFF Deep Woods insect repellent VIII
  • Cutter skinsations insect repellent
  • EcoSmart organic insect repellent
  • Cutter lemon eucalyptus insect repellent
  • Avon Skin So Soft Bug Guard
  • Avon Skin So Soft Bath Oil
  • Victoria Secret Bombshell
  • Mosquito skin patch (contains Thiamin B1)

The Repel, OFF and Cutter each contained DEET. The next five were natural repellents containing various active ingredients. Researchers tested the bath oil because of the urban myth that Skin So Soft repels mosquitoes, and the perfume to see if mosquitoes would be attracted to a floral scent. The patch tested the claim that vitamin B also repels mosquitoes.

Mosquito populations in each tube were counted immediately after release, then again at 30, 120 and 240 minutes.

Both Ae. albopictus and Ae. aegypti were repelled immediately by the DEET repellents, but OFF and Cutter lost effectiveness after 2 hours. Of the natural repellents, the Cutter lemon eucalyptus was the most effective and was even more effective than its DEET-based counterpart (Skinsations) and OFF. Avon Bug Guard repelled 50 percent more mosquitoes than the control hand, but it was not effective after 2 hours. Ecosmart was effective initially but lost effectiveness before 2 hours was up. The skin patch was not effective at all.

The surprise in the experiment was the mosquito reaction to the two perfumes. The bath oil, which purportedly repels mosquitoes, was ineffective against Ae albopictus and only partially effective against Ae aegypti. The Victoria Secret perfume, on the contrary, which contains fragrances of vanilla orchid, passion fruit and peony, was almost as effective as the Repel in the beginning at repelling mosquitoes. In fact, it didn’t lose effectiveness as a repellent until after 2 hours.

The two most effective repellents that lasted the entire 4 hours were Repel and Cutter lemon eucalyptus. Cutter contains a lemon eucalyptus oil and p-menthane-3,8-diol, a natural ingredient similar to menthol. It is also found in eucalyptus oil.

The researchers surmised that the floral perfume of the Victoria Secret scent may mask the human odor, making the person wearing it less desirable. However, it doesn’t last for the duration of the true repellents.

The study confirmed other studies that vitamin B1 is not a suitable insect repellent. Current articles on the Internet also agree that vitamin B1 has not been found to be an effective repellent.

Source: Stacy D. Rodriguez, Drake, L.L., Price, D.P., Hammond, J.I., and Hansen, I.A. (2015). The efficacy of some commercially available insect repellents for Aedes aegypti (Diptera: Culicidae) and Aedes albopictus (Diptera: Culicidae). Journal of Insect Science. 15(1): 140. DOI: http://dx.doi.org/10.1093/jisesa/iev125

 

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