Ray Eckhart is a Penn State Extension Educator in Franklin County with responsibilities for Consumer Horticulture, Forest Pest Management, and Vector Management (Ticks and Mosquitoes).
In last week’s blog, we learned about repellents with DEET and Picaridin. EPA classifies those repellents as “conventional repellents” and Oil of Lemon Eucalyptus (PMD), and IR3535 as “biopesticide repellents,” which are derived from natural materials, but don’t let that “natural” word fool you.
Oil of Lemon Eucalyptus is one of many “natural” products. Research has shown that repellents based on natural oils or herbs are less effective on mosquitoes than products based on picaridin or DEET. According to the Centers for Disease Control and Prevention, oil of lemon eucalyptus (active ingredient: p-menthane 3,8-diol [PMD]), tested against U.S. mosquitoes “provided protection similar to repellents with low concentrations of DEET.” The data showed that this was effective only for the first few minutes of the testing. After that, it was much less effective.
Oil of lemon eucalyptus should not be used on children younger than three years old.
So it turns out the natural products are not as effective, and not as safe as their synthetic counterparts. That covers the products that are registered for use on the skin.
A more recent product is the OFF clip on device. I did a review of this product back in 2009 on the Master Gardeners Franklin County blog, and don’t have a whole lot to add. The active ingredient in this case is the synthetic pyrethroid Metofluthrin. Michael Kauffman of Michigan State University has this to say:
A recently available personal barrier repellent, OFF clip-ons, also uses a pyrethroid type of insecticide (metofluthrin) dispersed with a small fan as a repellant. I recently tried using one of these units, but it was ineffective against the swarms of A. trivittatus that attacked my dog and me when we walked near the edges of the lawn or along country roads. It did appear to inhibit landing/biting attempts when I used it while sitting on the patio, but it did not eliminate repeated mosquito attacks to my head, face, and lower legs. I doubt most people will want to wear three of these units for full “coverage” and I suspect no one will want to wear one as a necklace to keep A. trivittatus away from the head and neck – the packaging label warns against inhalation of the vapors (something that’s probably hard to avoid, in my estimation). Unfortunately, there are no great options for barrier repellants yet. Landscaping plants and citronella candles have not been shown to be more effective than smoke producing candles in keeping mosquitoes at bay. However, research of area-wide repellants is a hot area, so expect to see more products of this type in the next few years.
If you’re sitting out on a deck, I tend to recommend to folks that they put up a good old fashioned fan. Mosquitoes are relatively poor flyers and a fan on high can keep them away from you without resorting to repellents of any kind.
Another way to protect yourself, without putting chemicals (natural or synthetic) on your skin, is to impregnate your clothes with something that repels, or kills the critters. The active ingredient in these products is the synthetic pyrethroid permethrin. Here is a quick YouTube video that shows how permethrin works on clothes.
In fact, Dr. Thomas Mather, professor of public health entomology at the University of Rhode Island, sponsor of the excellent web site TickEncounter.org, recommends permethrin products on clothes as the best way to keep ticks at bay – better than DEET. You can either buy clothing that is already treated, or follow the directions in these two videos: Soak Method or Spray Method.
No permethrin product labeled for use as a pesticide is labeled for use on the skin. But it’s important to keep that caveat in perspective. There are 1 % solutions of permethrin in over the counter products used to treat head lice and a doctor can prescribe 5% solutions of permethrin for the treatment of scabies. However, all products must be used according to their label.
I’d be remiss if I didn’t use this opportunity to dispel some of the myths that abound about other items touted as being able to repel mosquitoes. Here’s Snopes on some the household remedies that don’t work (Bounce, Lemon Joy, etc.) Here is a website from the Mosquito Control District located in Tangipahoa Parish, Louisiana that shows a scientifically designed experiment to test the Listerine myth. Just in case that isn’t enough, here are a few more websites to check out: University of Wisconsin, Purdue University and Rutgers University.
I hope this blog has given you some resources to check and figure out how you are going to repel mosquitoes this summer because they are here and will not be going away for quite a while!
Until next time,
Active Ingredients Found in Insect Repellents. U.S. Environmental Protection Agency. (2009)
Insect Repellents. University of New Hampshire. (2011)
Kauffman, M. The Summer of Our Discontent. Michigan State University Extension. (2009)