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DEET – Is It Safe?

DEET is the standard for repelling mosquitoes. Some people are looking for an alternative because they want something safer. That makes sense only if DEET is not already safe.

In some circles it is reported that DEET causes autism and neurological disorders. But is this really true? How safe is DEET?

DEET- Is It Safe

“I would not go canoeing without DEET” – the author, on the Coppermine River

DEET – What DO The Experts Say?

Deet has been in use for 55 years so scientists have had a lot of time to study the product and it’s effects on humans. Here is what the experts say:

The Environmental Working Group, after spending 18 months looking at all the options, recommends DEET as the best choice.  They say “DEET is widely used but much maligned.  DEET’s safety profile is better than many people assume. Its effectiveness at preventing bites is approached by only a few other repellent ingredients.” Their mission statement is “to empower people to live healthier lives in a healthier environment. With breakthrough research and education, we drive consumer choice and civic action.” (ref 1).

Centers for Disease Control, the CDC recommends DEET, as one of 4 acceptable products for the prevention of West Nile virus disease (ref 2).

The EPA did a safety review of DEET in 2014 and concluded that “The Agency has not identified any risks of concern to human health, non-target species or the environment”, (ref 3).

The World Health Organization considers DEET to be safe, but now recommends Picaridin as a better option.

There are cautions for children under the age of two months, but even the American Pediatric Society considers it safe for older children.

DEET – Does it Cause Neurological Disorders?

A common concern by people who feel DEET is not safe is a report that found it causes neurological disorders. Lots of web sites report this research, and none, that I looked at, provide a reference. They do mention Dr. Mohamed B. Abou-Donia, so I tracked down a number of his published work on DEET. See reference 4 as an example.

His work looks at the effect of dosing rats with DEET and another pesticide. His main point is that the combination of chemicals make them more dangerous to humans. Most people who use DEET are not exposed to pesticides at the same time.

In Dr. Abou-Doniathe’s experiments, rats are exposed to DEET, daily, for 60 days straight, at a dose of 40 mg/kg per day. Lets put that into perspective. If a 200 pound (90Kg) person was to receive the same exposure they would be exposed to 3.6 g each day.

I use a 30% Muskol product and use less than one 50 ml bottle in a season – and I am outside, gardening, almost everyday in summer. If I were to be treated like the rats in the experiment, I would have to use a bottle every 4 days. Or stated another way, I would use fourteen 50 ml bottles in 2 months.  Clearly the dose used in the experiment is far higher than what a normal individual uses.

What does Dr. Mohamed B. Abou-Donia say about the safety of DEET? According to Duke Medicine (ref 5) he said “If used sparingly, infrequently and by itself, DEET may not have negative effects – the literature here isn’t clear, But frequent and heavy use of DEET, especially in combination with other chemicals or medications, could cause brain deficits in vulnerable populations.”

The scientist who did the work to detect neurological disorders, feels that occasional use is probably safe. So much for all of the fear mongering headlines that claim DEET causes neurological disorders!

The work of Dr. Mohamed B. Abou-Donia was available to the EPA for the 2014 review, and it did not cause them to be concerned.

Does DEET Cause Cancer?

There is no evidence that DEET causes cancer. But if you look at the MSDS (material safety data sheet) for DEET products, you might notice that DEET is usually dissolved in ethyl alcohol – the alcohol we drink. The MSDS report says the alcohol is a carcinogen, but that DEET is not.

So the beer you drink while walking in the woods is more likely to give you cancer than the DEET you are wearing.

What Happens to DEET in The Body?

When evaluating the danger of a chemical it is useful to understand how our body deals with the chemical. A chemical that accumulates in the body, like mercury, is more harmful than one that does not accumulate. If it interacts chemically in a dangerous way, the original chemical may be safe, but the reaction products it creates may not be.

DEET is absorbed through the skin. A mixture of DEET and alcohol, as in Muskol which I mentioned above, absorbs more readily through the skin than DEET without alchohol.  Drinking alcohol may also cause more DEET to be absorbed through the skin. Sunscreen products that contain DEET may cause more DEET to be taken into the body through the skin.

The DEET that is taken into the body can be found in the blood up to 24 hours after it is applied to the skin. Once in the body, DEET is broken down by the liver into smaller harmless chemicals and then eliminated from the body mainly through the urine. Nearly all of the DEET is eliminated by the body within 24 hours of applying it.

In summary, it seems as if our bodies are quite able to handle any DEET that is absorbed.

Conclusion

DEET smells, and it is oily. It dissolves some types of plastic. It is no wonder that some people think it is a dangerous chemical. But the facts are quite clear. Occasional use of DEET is quite safe and it is one of the most effective ways to reduce mosquito bites.

For information on options other than DEET, have a look at Mosquito Repellents – Best Options.

Keep in mind that any new option, natural or man-made, has had very limited testing compared to the testing that has been done on DEET. It may be better to stick with the devil you know, and trust, than to dance with the new devil on the street.

References:

1) The Environmental Working Groups Guide to Bug Repellants: http://www.ewg.org/research/ewgs-guide-bug-repellents

2) Center For Disease Control – Protection Against Mosquitoes: http://wwwnc.cdc.gov/travel/yellowbook/2014/chapter-2-the-pre-travel-consultation/protection-against-mosquitoes-ticks-and-other-insects-and-arthropods

3) EPA position on DEET: http://www2.epa.gov/insect-repellents/deet

4) Subchronic Dermal Application of N,N-Diethyl m-Toluamide (DEET) and Permethrin to Adult Rats: http://www.sciencedirect.com/science/article/pii/S0014488601978070

5) Duke Medicine on DEET: http://corporate.dukemedicine.org/news_and_publications/news_office/news/5500

6) Photo Source: Robert Pavlis

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Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

9 Responses to 'DEET – Is It Safe?'

  1. Brent Ferris says:

    Your Ref #4 does say “neurodegeneration was significantly greater with exposure to DEET alone” — however I agree, that 40 ml/kg of body weight is serious overkill, and with that much exposure, the liver is probably over-toxified. The ethyl alcohol DEET is combined with can likely affect brain tissue, and if the liver is over loaded, then excess amounts of DEET can prob then affect brain function. I used to work in the N. Ontario bush, and a bottle of DEET (50% or more containing DEET) would typically last longer than the season, even when applied 2x per day. It seems to me the research should also have included a typical person’s exposure to it, 40 ml/kg would amount to 4 litres of exposure every day — Ludicrous.

    • A lot of research uses high doses in order to more easily see effects. There is nothing wrong with this approach so long as the researchers qualify the results. The problem is that not all do this, but more likely is the fact that newspapers, and web sites, only look at the results and not the concentration. As a result they then spread false information.

      Everything to do with chemicals is concentration based.

  2. Tori says:

    “The Environmental Working Group, after spending 18 months looking at all the options, recommends DEET as the best choice. They say “DEET is widely used but much maligned. DEET’s safety profile is better than many people assume. Its effectiveness at preventing bites is approached by only a few other repellent ingredients.” Their mission statement is “to empower people to live healthier lives in a healthier environment. With breakthrough research and education, we drive consumer choice and civic action.” (ref 1).”

    The EWG listed DEET as one of 4 best choices. In fact, they listed 2 of the other chemicals, Picaridin and IR3535, as “a good DEET alternative with many of the same advantages and fewer disadvantages.” The fourth choice, Oil of Lemon Eucalyptus, is an all natural alternative. It’s only disadvantage is its lack of safety testing therefore it is not proven to be safe.

    Maybe you should read your sources more carefully before posting false information to unknowing readers.

    • I don’t understand you comment.

      The quote in the first paragraph can be found on page 3 of their report, which can be accessed at the top of the on the link I provided.

      The list of the 4 ingredients mentioned in paragraph 2 is on page 4 of the report. The last sentence of the second paragraph comes from page 10 of the report.

  3. rogerbrook says:

    It all sounds so familiar. Irrational worries about pesticides. Keep up the good work Robert.

  4. Jim says:

    I can say that a DEET-containing bug spray removed the clear coat (nitro-cellulose laquer) from a 1992 Gibson Flying V when I was younger where my hand touched the body. Not necessarily bad for humans – but not so good for guitars. The lesson: one should not jam in a garage in the middle of summer during insect season.

  5. Indeed DEET has undergone rigurous testing and although I am very much pro-plants in everything, regarding the subject I adhere to this: “it cannot be assumed that natural equates to safe” – here’s one more link with interesting facts on the subject plant-based repellents/DEET – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3059459/

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