 |
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]
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
“Does Insect Repellent
Expire?” [PestControlFaq.com, 2019]
Sawyer Maxi-DEET Safety Data Sheet
