Not all bug repellents are equal

Pay attention to the ingredients of bug sprays and other repellents, because they're not equally effective at warding off mosquitoes that carry diseases like Zika virus, researchers say.

Products with DEET or oil of lemon eucalyptus, which contains an ingredient known as PMD, are more effective at repelling the Aedes aegypti mosquito that carries Zika, chikungunya, yellow fever and dengue, researchers found.

Wearable devices advertised as mosquito repellents should largely be avoided, their data suggest.

With the recent outbreak of Zika virus, many mosquito repellents became best-selling products, said Immo Hansen, of New Mexico State University in Las Cruces, the senior member of the research team.

"They're very popular," Hansen told Reuters Health, citing the number of products for sale just on Amazon.com.

For the new study, researchers purchased and tested 11 products from Amazon.com and local stores in New Mexico. Altogether they tested five wearable devices, five sprays and one candle, using human volunteers who hadn't bathed or used deodorant for at least 15 hours before the experiments.

The tests were conducted in wind tunnels. Fifteen minutes after releasing the mosquitoes, the research team counted how many bugs had come close to the participant, to determine how many were attracted to the person's smell.

Without any type of device or spray in the tunnel, about 89 to 91 percent of the mosquitoes were attracted to the volunteers, depending on how far away they sat from where the insects were released.

Of the five wearable devices, only one - the OFF! Clip-on - significantly reduced the number of mosquitoes drawn to the participants' scents. The attraction rate was only about 27 percent when people were one meter from the cage. The device uses a fan to disperse an insect-repelling chemical known as metofluthrin.

The other wearable devices included a speaker to repel mosquitoes and three bracelets that emitted different oils.

"None of the bracelets had any effect on reducing attraction," said lead author Stacy Rodriguez, who is also affiliated with New Mexico State University.

All of the spray-on repellents significantly reduced the number of mosquitoes attracted to the participants, with attraction rates varying from about 30 percent (with Cutter Lemon Eucalyptus and Ben's Tick & Insect Repellent) to about 79 percent. The tested spray-ons generally used DEET or oils like lemon eucalyptus.

Like many of the wearable devices, the candle that contained citronella oil did not significantly reduce the number of mosquitoes attracted to participants' scents.

The products' popularity and their ineffectiveness suggests there are not enough regulations in place to protect consumers, said Hansen.

The researchers write in the Journal of Insect Science that consumers may feel a false sense of comfort that they are protected by these devices when they actually are not.

"I think (it's) definitely important to look at the active ingredients before you purchase something," said Rodriguez.

The researchers caution that additional studies are needed since they only used female Aedes aegypti mosquitoes.

SOURCE: http://bit.ly/2liHp1y Journal of Insect Science, online February 16, 2017.