Forget DEET, Fight Mosquitoes Naturally
Forget DEET, because it appears some mosquitoes do. A new study has indicated that some mosquitoes quickly turn up their nose at the toxic insecticide, so it may be time to consider how to fight mosquitoes naturally.
Why mosquitoes forget DEET
In the new study, which was conducted at the London School of Hygiene and Tropical Medicine, scientists found that some mosquitoes became less sensitive to DEET (N,N-diethyl-meta-toluamide) within three hours of their first exposure to the chemical. That is, when a group of mosquitoes were re-introduced to an arm treated with DEET for a second time, they were less likely to be deterred.
More specifically, the scientists observed that “insensitivity to DEET on a second exposure…initially suggested they may have adapted to DEET…and were able to ‘overcome’ the natural repellent effect.” Testing of the mosquitoes led the researchers to discover it appears something is altered in the olfactory (smell) system of the insects that causes them to be less affected by the smell of DEET after first exposure.
DEET, which was originally developed for wartime use in 1946, is a toxin that works like a paralyzing nerve gas. The enemies are mosquitoes (which carry malaria and West Nile virus) and ticks (Lyme disease).
Although the Environmental Protection Agency (EPA) argues that DEET is safe when used as recommended, other agencies and individuals believe DEET poses health risks to users. A previous study, for example, noted that DEET blocks the activity of an enzyme that is critical for optimal functioning of the central nervous system.
Natural mosquito repellents
One of more original natural ways to help keep mosquitoes away is to use dryer sheets. A Kansas State University study found that use of Bounce dryer sheets (Outdoor Fresh Scent™) was effective in reducing the attraction of fungus gnats.
An analysis of the dryer sheets revealed they contained high levels of an ingredient (beta-citronellol) found in citronella (an essential oil in lemongrass), rose geranium, and lemon balm, three plants whose essential oils are frequently used to help repel mosquitoes (see below). They also found a compound called linalool that is present in basil, lavender, and marjoram. Linalool is toxic to insects.
Essential oils and their components have long been regarded as somewhat helpful in repelling mosquitoes, but some appear to be more effective than others. In a study from The Hebrew University, researchers compared the effectiveness of citronella, linalool, and geraniol in diffusers and candles.
The candles contained 5% of the active ingredient while the diffusers contained 100%. Repellency rates indoors were significantly better with the diffusers than with the candles.
For example: 14% for citronella candles vs. 68% for diffusers; 50% vs 97% for geraniol; and 93% for linalool diffusers (no candles available). Geraniol also performed more than twofold and threefold better outdoors than did linalool or citronella diffusers in repelling mosquitoes.
Both rose-scented geraniums and lemon balm (Melissa officinalis) contain citronellal (the liquid extracted from citronella) and geraniol. Some people reportedly crush lemon balm leaves and rub them on their skin before going outside.
The leaves of other herbs also can be crushed and rubbed on the skin to provide temporary (30 minutes or so) of protection against mosquitoes. Those herbs include basil (Ocimum basilicum), lemongrass (Cymbopogon citratus), and lemon thyme (Thymus x citriodorus). Of course, do not use these herbs if you are allergic to them, and test a tiny area of your skin to see if you react before rubbing the herbs over a larger surface area.
Here are a few other ways to fight mosquitoes naturally.
- Combine 1 part of any one of these essential oils (cinnamon, lemongrass, lemon eucalyptus) with 10 to 20 parts oil (sunflower, olive, canola) or alcohol (witch hazel, vodka) in a spray bottle. Shake well and spray the repellent onto your skin. Reapply about every 60 minutes. Store the repellent in a dark bottle and away from heat.
- Mix 1 tablespoon of vanilla extract in 8 ounces of water and put in a spray bottle. Spritz yourself with the mixture as needed.
- Eat fresh garlic. Your skin and sweat will release a garlicky odor and hopefully keep mosquitoes away (but it may keep friends away as well!)
- If possible, sit or stay near a blowing fan, since mosquitoes are weak flyers.
Mosquito season is just around the corner, so be prepared. Some mosquitoes seem to ignore DEET, and you may want to as well. This may be the year you forget DEET and fight mosquitoes naturally.
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Cloyd RA et al. Bounce fabric softener dryer sheets repel fungus gnat, Bradysia sp. Nr. Coprophila (Diptera: Sciaridae), adults. HortScience 2010; 45:1830-33
Corbel V et al. Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent DEET. BMC Biology 2009; 7:47
Muller GC et al. Efficacy of the botanical repellents geraniol, linalool, and citronella against mosquitoes. Journal of Vector Ecology 2009 Jun; 34(1): 2-8
Stanczyk NM et al. Aedes aegypti mosquitoes exhibit decreased repellency by DEET following previous exposure. PLoS ONE 2013; 8(1): e54438