Let’s talk about DEET.


During this time of the year, everyone is going camping or is outdoors. You walk into a local store to find something to prevent the bugs from biting you.


“What is the best repellent?”


You will find that there are dozens of bug repellents out there. If I were to go into details about all of them this article would be pages long. So I decided to focus on the most popular ingredient - DEET. DEET is the gold standard in preventing mosquito bites and is used in many countries to prevent the spread of Zika Virus, Malaria, and Lyme disease. As a result I typically recommend DEET containing products for individuals travelling or going camping.


“How does DEET work?"


Interestingly, past belief is that DEET stops insects from detecting you, which technically should have stopped DEET from being classified as a “repellent.” But more current research has shown that all insects, including ticks, and mosquitoes really do not like the smell of DEET and actually avoid it.


“There are many different products that contain DEET, which is the best one to choose?”


It really depends on the age of the person you are applying DEET to, and how long you want the protection for.


You will find that there are repellents that range from 2% up to 30%.


To choose the right concentration, the first factor you have to consider is age.


Health Canada recommends:

  • Adults and Children >12 years of age can use up to 30% DEET, for protection up to 8 hours to a maximum of 3 applications daily.

  • Children 2 - 12 years of age can use up to 10% DEET for protection up to 3 hours for each application, up to 3 applications daily.

  • Children 6 month - 2 years of age can apply up to 10% DEET, but only ONCE per day.

  • Below 6 months, do not use any DEET containing products.

It is a misconception that the higher the concentration of DEET the better it works, but really, the higher the concentration of DEET, simply means how long the DEET will ward off insects.


As a result the second factor you need to consider is how long you want to be protected for.

  • 30% DEET protects 5-8 hours

  • 15% DEET protects 3.5-5.5 hours

  • 10% DEET protects 2.5-3.5 hours

  • 5% DEET protects 1.5-2.5 hours

You may find DEET products that are in the 50% or higher, but as DEET level goes up, there are diminishing returns. Above 30% the protection time does not substantially increase, and you would have exposed yourself to more DEET than you need.


“Does DEET cause seizures/diarrhea/nausea/coma/toxicity?”


This is a very common question I get about DEET, which turns away some people from using these repellents. With full disclosure, technically DEET can cause these problems, however you would have to swallow the DEET in order to get enough into your blood to cause these problems (Koren et al, 2003). That is not to say that you should bathe in DEET, but the majority of these issues come from accidentally ingesting the repellent.


This means two things. If you apply DEET using your hands, wash them off before using them to eat anything. The same applies to small children who are more likely to put their hands in their mouths.


“Are bug repellents containing DEET safe for pregnant/lactating women?”


The answer is that it is likely to be safe. There is good data saying that DEET is safe for pregnant women who are in their second and third trimester (Koren et al., ,2003; McGready, 2001), but there is no concrete human data regarding whether it is safe for women in their first trimester. Oddly enough Health Canada’s website does not really have a statement on whether or not DEET is safe for pregnant women. Fortunately, the Center for Disease Control (CDC) recommends using DEET containing repellents for all stages of pregnancy regardless of this fact (Mutebi, Hawley & Brogdon, 2017). Given that mosquitoes and ticks are carriers of very serious diseases that may be harmful to the fetus, I would also agree with this statement.


Finally, there is also little evidence that DEET applied appropriately can cause harm to a baby while a mother is breastfeeding, and is therefore safe (Koren et al, 2003).


“I have heard of DEET, what is Picaridin/Icaridin?”


Picaridin/icaridin has technically been around for a while, but it’s not as popular as DEET in Canada. There have been a lot of studies comparing DEET and Picaridin, and they both do a good job at repelling mosquitoes (Scott et al, 2014; Onyett, 2014). Picaridin/icaridin is not greasy and does not dissolve or weaken plastic materials (ie: tents, fishing lines etc…). The dosing of the product is simpler as its dosage depends on the length of time you want the protection as long as the person is older than 6 months.

  • If you want protection for 5 hours you can use 10% up to four times daily.

  • If you want protection for 7 hours you can use 20% up to twice daily.

Picaridin has as a similar story to DEET. Virtually all the reported side effects of Picaridin were from individuals that had accidentally ingested the repellant (Charlton, 2016). CDC also recommends it to pregnant women.


TAKE AWAY POINTS:


  • DEET, and Picaridin/Icaridin, containing products are the gold standard for bug repellents. They are recommended by the CDC to prevent the spread of Zika, West Nile disease, and Lyme disease.

  • Their dosing is based on age and how long you want the protection, and they are most likely safe for pregnant/lactating women.

  • They can have side effects, but more likely if they are being accidentally ingested. Therefore avoid applying the product to children’s hands and avoid applying it on animals.



References:

Mutebi, J-P., Hawley, W.A., Brogdon, W.G. (2017). Protection against Mosquitoes, Ticks and other Arthropods. Centers for Disease Control and Prevention.


Onyett, H., & Canadian Paediatric Society, Infectious Diseases and Immunization Committee (2014). Preventing mosquito and tick bites: A Canadian update. Paediatrics & child health, 19(6), 326–332.


Nathan P. Charlton, Lauren T. Murphy, Jennifer L. Parker Cote & J. Priyanka Vakkalanka (2016) The toxicity of picaridin containing insect repellent reported to the National Poison Data System, Clinical Toxicology, 54:8, 655-658


Scott,J.M., Hossain,T., Davidson,C., Smith,M.L, Xue, R. (2014). Laboratory evaluation of Citronella, Picaridin, and Deet repellents against Psorophora ciliata and Psorophora howardii. Journal of American Mosquito Control Association. 30(2): 136-137.


Stacy D. Rodriguez, Hae-Na Chung, Kristina K. Gonzales, Julia Vulcan, Yiyi Li, Jorge A. Ahumada, Hector M. Romero, Mario De La Torre, Fangjun Shu, Immo A. Hansen. (2017). Efficacy of Some Wearable Devices Compared with Spray-On Insect Repellents for the Yellow Fever Mosquito, Aedes aegypti (L.) (Diptera: Culicidae). Journal of Insect Science, Volume 17, Issue 1, January 2017, 24,


Koren, G., Matsui,D., Bailey,B. (2003). DEET-based insect repellents: safety implications for children and pregnant and lactating women . CMAJ. 169(3), 209-212.


McGready R, Hamilton KA, Simpson JA, Cho T, Luxemburger C, Edwards R, et al. (2001). Safety of the insect repellent N,N-diethyl-M-toluamide (DEET) in pregnancy. Am J Trop Med Hyg 2001;65:285-9.

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