A Question About DEET, Does It Have A Shelf Life?©

Various half used DEET containing products, from the author’s collection, picture by the author.

While I was in Algonquin two weeks ago, I was asked, “Does DEET have an expiration date, this doesn’t smell right?”

I didn’t know the answer to this question, but since it was my bottle of DEET, I knew that it was more than ten years old, so when I got back to internet-land, I decided to do some research.

Why you need to use DEET, or some other insect repellent, a lonestar tick on the author’s leg, picture by the author.

The few sources that I found, reported that the U.S. Federal Government does not require an expiration date on DEET based products, because a U.S. Military study determined that DEET was very stable and that the cream form is shelf stable for at least five years and the stick form indefinitely.¹ In fact, Sawyer, on page 6 of their Safety Data Sheet for Maxi-DEET, stated that DEET was stable and that there was “No dangerous reaction known under conditions of normal use”.²  From the literature, that I could find DEET will remain stable indefinitely; however the creams and solvents that it is mixed with can degrade, with some manufacturers stating that the feel, smell and appearance of their products may change after three years. 

So what do you do if you have some DEET containing product that you are unsure of and that you want to dispose of: how do you safely throw it out?  On my SAWYER^® Insect Repellent 30% DEET aerosol can, it says to dispose of the empty can in a recycling bin and on pestcontrolfaq.com, it recommends pouring any non-aerosol spray into kitty litter, before disposing of it in your trash.³

Just in case you have never used DEET or are unfamiliar with it, here is some background information.

DEET, or N,N-diethy-3-methylbenzamide, was developed by the U.S. military in 1946 as an insect repellent, and was released to the civilian market in 1957.  It is a broad-spectrum insect repellent that repels most mosquitoes, biting flies, ticks, fleas and chiggers.  It is considered to be the most effective insect repellent available for human use, although, in 2005 when this statistic was released, picaridin was not available in the U.S. market: picaridine is a widely used alternative to DEET.^4,5,6  In 2005, it was estimated that 30% of the population of the United States applies DEET each year, and in 2014 researchers estimated that people put on DEET 200 million times a year world wide.^7,8  In mosquitoes, DEET works by interfering with the neurons and receptors located on their antennae and in their mouth, that detect carbon dioxide and lactic acid: basically it blocks the insects sense of smell and makes hard for them to find your exposed skin.^9,10 

Many people are concerned with the proper percentage of DEET to use and this leads to the question of absorption and how long the repellent protection will last. 

DEET is absorbed through your skin and the absorption depends on a number of factors, such as the concentration of DEET and the solvent that is used.  Many products use ethanol as a solvent, and since ethanol increases the permeability of the skin, DEET absorption into the body may be increased with these products.  The Utah Poison Control Center reported on a study that showed an average absorption of 8.4%, two hours after application to the skin of 15% DEET in ethanol, while after using 100% DEET on the skin, an average absorption of 5.6% was reported.¹¹ 

Also, the Utah Poison Control Center reported that applying DEET to broken skin will increase its absorption through the skin into the body and that absorption decreases under conditions of elevated body heat and perspiration.¹²  DEET does not accumulate within your body, but is metabolized and excreted in your urine, and it has been found that rate of elimination is faster than the rate of absorption, with elimination complete within twelve hours.¹³

The higher the concentration of DEET in a product, the longer the protection time that it provides, however, a higher concentration does not mean that the product works better: a 7% DEET concentration repelling mosquitoes for up to two hours and a 98.25% solution of DEET repelling mosquitoes for up to ten hours¹⁴.  The U.S. Center for Disease Control (CDC) reported that protection time reached a plateau when the concentration of DEET approached 50%¹⁵, and interestingly the Utah Poison Control Center noted that products that used ethanol as a solvent had an increased protection time¹⁶.

As long as DEET is used as directed, there are few adverse effects, however if you get it into your eyes or mouth you will experience “local irritation and discomfort” in the words of the Utah Poison Control Center.  DEET has not been found to cause severe or long-term damage to the eyes, in tests on animals, and getting small amounts of DEET into your mouth does not usually cause toxic effects, according to experts.  While studies have shown that DEET can cross the placenta, the exposure to unborn children has not proven to be significant and the U.S. CDC recommends that pregnant and lactating women, who live in areas with disease causing insects, use DEET to protect themselves and their children, both born and unborn.¹⁷  Also, per the CDC as long as the user follows the usage directions on the label and uses the product safely, DEET should not be harmful.^18,19

Recommendations and Guidelines for the use of DEET containing products, from the U.S. Center for Disease Control and the American Academy of Pediatrics

·       Apply DEET only when planning to be outdoors in mosquito infested areas

·       Use the appropriate concentration of DEET.  Children in the general public should use 30% or less.  A product with a concentration of 10% or less may be more appropriate for children under 12 years.

·       Do not apply DEET to children under 2 months of age.

·       When using on children, apply to your own hands and then put it on the child.

·       Do not apply it to children’s hands.

·       Do not allow children to handle products containing DEET.

·       Do not apply over cuts, wounds or irritated skin.

·       Do not apply near eyes and mouth.  Apply sparingly around ears.

·       Reapply DEET only as directed by packaging.  The effective duration depends on the concentration of DEET in the product.  Avoid over-application of DEET products.

·       Use just enough DEET to cover exposed skin and or clothing.

·       Do not use on skin, under clothing.

·       After returning indoors, wash treated skin with soap and water.

·       Wash treated clothes before wearing again.

·       Do not apply a combination product containing sunscreen and DEET.

·       Do not spray aerosol or pump DEET containing products in enclosed areas.

·       Do not apply aerosol or pump DEET containing products directly to your face.  First spray it on your hands and then rub them carefully over your face, avoiding your eyes and mouth.

I hope that you continue to enjoy The Woodsman’s Journal Online and my videos at BandanaMan Productions and don’t forget to follow me on both The Woodsman’s Journal Online and subscribe to BandanaMan Productions on YouTube, and if you have questions, as always, feel free to leave a comment on either site.

Notes

¹  “Shelf-life of DEET-based products...?” [Lonely Planet, 2019]

Lonely Planet reported eleven years ago that the U.S. Military had done studies on the shelf-life of DEET and the report could be found at http://www.deetonline.org/faq.php#q20 and at

www.nehc.med.navy.mil/nepmu2/pmttoolbox/ENTOMOLOGY_ files%5CShipboard%20Pest%20Control%20Manual%5C03%20DAT, however neither site returns any information and I was unable to locate this report, so unfortunately this information is anecdotal.

²  Sawyer Maxi-DEET Safety Data Sheet

³  “Does Insect Repellent Expire?” [PestControlFaq.com, 2019]

⁴  “DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005]

This information was referenced from the following, by the Utah Poison Control Center, Fradin MS, Day JF, Comparative Efficacy of Insect Repellents Against Mosquito Bites, [N Engl J Med, 2002] 347:13-18.

⁵  “Does Insect Repellent Expire?” [PestControlFaq.com, 2019]

⁶  Diep, Francie, “Is DEET Safe To Use? Yet another review of the science answers: Yes.”[Popular Science, A Bonnier Corporation Company, 2019]

⁷  “DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005]

This information was referenced from the following, by the Utah Poison Control Center, Osimitz TG & Murphy JV, Neurological effects associated with use of the insect repellent N, N-diethyl-m-toluamide (DEET) [J Toxicol Clin Toxicol 1997] 35:435-441

⁸  Diep, Francie, “Is DEET Safe To Use? Yet another review of the science answers: Yes.”[Popular Science, A Bonnier Corporation Company, 2019]

⁹  “Does Insect Repellent Expire?” [PestControlFaq.com, 2019]

¹⁰  “7 myths and facts about deet” [S.C. Johnson & Son, 2019]

¹¹  “DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005]

This information was referenced from the following, by the Utah Poison Control Center, Selim S, et al. Absorption, Metabolism, and Excretion of N,N-Diethyl-mtoluamide Following Dermal Application to Human Volunteers, [Fundam Appl Toxicol, 1995] 25:95-100 and Sudakin DL, Trevathan WR, DEET: A Review and Update of Safety and Risk in the General Population, [J Toxicol Clin Toxicol, 2003] 41:831-839

¹²  Ibid

This information was referenced from the following, by the Utah Poison Control Center, Fradin MS, Day JF, Comparative Efficacy of Insect Repellents Against Mosquito Bites, [N Engl J Med, 2002] 347:13-18.

¹³  Ibid

¹⁴  “7 myths and facts about deet” [S.C. Johnson & Son, 2019]

¹⁵ “Fight the Bite for Protection from Malaria Guidelines for DEET Insect Repellent Use” [CDC]

¹⁶  “DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005]

¹⁷  Ibid

This information was referenced from the following, by the Utah Poison Control Center, Sudakin DL, Trevathan WR, DEET: A Review and Update of Safety and Risk in the General Population, [J Toxicol Clin Toxicol, 2003] 41:831-839

¹⁸  “Fight the Bite for Protection from Malaria Guidelines for DEET Insect Repellent Use” [CDC]

¹⁹  “DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005]

Sources

“7 myths and facts about deet” [S.C. Johnson & Son, 2019] https://off.com/en/education/active-ingredients/7-myths-and-facts-about-deet, accessed 8/1/2019

“DEET Insect Repellant Toxicity”, Utox Update, Volume 7, Issue 2 [Utah Poison Control Center, 2005] https://poisoncontrol.utah.edu/newsletters/pdfs/toxicology-today-archive/Vol7_No2.pdf, accessed 8/1/2019

Diep, Francie, “Is DEET Safe To Use? Yet another review of the science answers: Yes.”[Popular Science, A Bonnier Corporation Company, 2019] https://www.popsci.com/article/science/deet-safe-use/, accessed 8/1/2019

“Does Insect Repellent Expire?” [PestControlFaq.com, 2019]

https://pestcontrolfaq.com/does-insect-repellent-expire/, accessed 8/1/2019

“Fight the Bite for Protection from Malaria Guidelines for DEET Insect Repellent Use” [CDC] https://www.cdc.gov/malaria/toolkit/DEET.pdf, accessed 8/1/2019

Sawyer Maxi-DEET Safety Data Sheet

https://sawyer.com/wp-content/uploads/2017/12/SDS-SP711-SP712-SP713-SP714-SP717-SP718B-SP719-MAXI-DEET-100-Sawyer-2018-05-04.pdf, accessed 8/2/2019

“Shelf-life of DEET-based products...?” [Lonely Planet, 2019], https://www.lonelyplanet.com/thorntree/forums/health/topics/shelf-life-of-deet-based-products, accessed 7/29/19