DEET Causes Problems in Humans

A number of expats visiting and living in Mexico swear by DEET.  Here are a few insights on DEET from respected experts.

“DEET is a good chemical for protection against insects, but prolonged exposure results in neurological damage, and this is enhanced by other chemicals and medications.**”
Bahie Abou-Donia of the Duke University Medical Center (Aug, 2009)

DEET   (N,N-diethyl-3-methylbenzamide),   slows or halts the actions of the enzyme acetylcholinesterase   in both insects and mammals.    This enzyme is typically found between nerve and muscle cells,   breaking down a messenger molecule after it has passed information from one cell to another.    If the messenger isn’t properly recycled, it can build up and lead to paralysis.
From Science News:  DEET’s Nastiness Extends to Humans
(Yes, that’s the official title of the Science News article- it is not my choice of titles.)

**Interactions with other chemicals: Other studies have shown that combining sunscreen with DEET caused skin to absorb DEET insect repellent more than three times faster than when used alone. This means that products with “safe” or low levels of DEET likely cause long-term neurological damage when used with common sunscreens.  Other studies have shown a 6X more rapid absorption of DEET and 3-4X higher amounts of DEET absorbed by the human body.
From the journal “Drug Metabolism and Disposition”:  Insect Repellent Interactions: Sunscreen…

The American Academy of Pediatrics (AAP) has issued guidelines regarding DEET use in children. It recommends avoiding DEET in children <2 months of age. For all other children, it advises using DEET with a concentration between 10% and 30%.
American Academy of Pediatrics.

“DEET should not be used in a product that combines the repellent with a sunscreen. Sunscreens often are applied repeatedly because they can be washed off. DEET is not water-soluble and will last up to 8 hours. Repeated application may increase the potential toxic effects of DEET.”

“Other precautions
Apply DEET sparingly on exposed skin; do not use under clothing.

Do not use DEET on the hands of young children; avoid applying to areas around the eyes and mouth.

Do not use DEET over cuts, wounds or irritated skin. Wash treated skin with soap and water after returning indoors; wash treated clothing.

Avoid spraying in enclosed areas; do not use DEET near food.”
From The American Academy of Pediatrics:  Follow Safety Precautions When Using DEET

Alternatives to DEET:
Autan is widely available here, and past studies have not found the problems associated with DEET – (but only time will tell on Autan’s long-term safe use).

There are 2 other decent (safer) alternatives to DEET:
Permethrins: “Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin.

“Oil of lemon eucalyptus [active ingredient: p-menthane 3,8-diol (PMD)], a plant- based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.
From US Centers for Disease Control (CDC):  West Nile Virus: Questions & Answers

And yes the Canadian & US military use DEET, but a 1990’s research program by a US Dept. of Ag. guy (in Florida) found he could reproduce roughly half of Gulf War Syndrome symptoms by combining DEET with the sunscreen they used during Desert Storm. Strangely, his previous 15 years of accepted research results were all suddenly called into question, he was summarily fired, and the program linking DEET/Pesticides/Sunscreen was immediately terminated. In that politically correct era’s wrangling, his DEET research results were buried and neglected until the early 2000’s when it again became acceptable to question such things.
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Disclosure: Since 1976 I have been an Environmental and Public Health Chemist performing both academic and private laboratory investigations of pesticides, industrial and radiological contaminants, and their Public Health consequences.
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These bits of information point to spraying clothing with DEET, or buying permethrin-treated clothing, and considering only limited DEET-skin applications, especially if you also use sunscreens.

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Notes:
Canadian regulations limit insect repellents to no more than 30 percent DEET. Based on the results of the past few years studies, people should likely not use United States formulations with higher percentages, where 100 percent DEET repellents are allowed.

Or, keep a high-voltage mosquito racquet on-hand: 100% effective at killing mosquitoes, especially when swung-upward, attacking from beneath flying mosquitos. (only $2.99 at Harbor Freight) (Mosquitoes aren’t programmed to avoid attacks from below.)

Create a Mosquito Spa!

A dish of water placed outside near the entrance/exit to your home makes a great watering hole for the rascals, the combination of your CO2 coming out the screeen/doorway plus a place to breed and drink = attracting nearly all nearby blood-suckers for easy spanking with your racquet. If you add some loosely-tented/bunched-rugs in a cool corner near the water-hole (aka dog dish), then the mosquitoes will rest and relax in the rugs (astro-turf doesn’t seem to mold) – giving them a nice holiday, before you shake the rugs and swing your racquet.

If you I spank 20-30 every morning around our dog’s dish: a good low-impact workout, whirling and gyrating to chase ’em, then you’ll not only remain fit; practice maintaining balance in a free-form sort of Tai Chi; but you might even entertain the neighbors.

Fortunately, our Dengue carrying A. ae. mosquitoes mainly bite in the morning and not at night.

Time to go work on my back-hand!
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A few other oldie but goodie references:
Koren G, Matsui D, Bailey B. DEET-based insect repellents: safety implications for children and pregnant and lactating women. CMAJ 2003;169:209-212. Erratum in: CMAJ 2003;169:283.

Osimitz TG. Murphy JV. Neurological effects associated with use of the insect repellent N,N-diethyl-m-toluamide (DEET). J Toxicol Clin Toxicol. 1997;35(5):443-445.

Ross EA. Savage KA. Utley LJ. Tebbett IR. Insect repellant interactions: sunscreens enhance deet (N,N-diethyl-m-toluamide) absorption. Drug Metabolism & Disposition. 2004; 32(8):783-785, 2004 Aug.

Fradin MS, Day JF. Comparative efficacy of insect repellants against mosquito bites. N Engl J Med 2002; 347:13-18.

Feel free to copy with proper attribution: YucaLandia/Surviving Yucatan.
© Steven M. Fry

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