Let me start by staying that writing this article changed the way I view insect repellents. You may also be surprised.
Before going on a picnic or watching fireworks, many of us will apply insect repellent this summer to ourselves or our children out of concern for mosquito-borne illnesses such as West Nile Virus or tick-borne illnesses like Lyme Disease. What does the evidence say about the safety of insect repellents?
The Centers for Disease Control and Prevention (CDC) has released recommendations related to the use of insect repellents especially for the prevention of tick and mosquito-borne infections. The CDC recommends the use of repellents containing the active ingredients which have been registered with the U.S. Environmental Protection Agency, including DEET (N,N-Diethyl-meta-toluamide), picardin, IR3535, and some oil of lemon eucalyptus products.
DEET is used by 1 in 3 of us each year
DEET was developed by the U.S. Army and registered for use by the public in 1957. It is also known as, N,N-diethyl-meta-toluamide and is the active ingredient in many insect repellent products.
DEET is designed to be applied directly to the skin and actually works by making it harder for bugs to smell us and find us.
In 2014, the EPA conducted its own safety review of DEET. The human health risk assessment concluded that there are no risks of concern because no toxic effects have been identified when the insect repellent is applied to the skin.
What does the evidence say?
In 1979, a paper published in the Journal of Pediatrics covered two case reports of children with possible encephalopathy, signs of confusion, weakness and behavioral changes due to DET or N,N-Diethyltoluamide. One case involved a 5 year old girl who had the chemical applied nightly due to concern of mosquitos. Since that time, the safety of insect repellents has been questioned.
Another case report describes respiratory distress and seizures that developed in an 18-month-old boy following brief exposure to low-strength DEET. The authors concluded that after a review of literature surrounding DEET, that it is not safe when applied to children’s skin and should be avoided in children.
Following these concerning reports and discovery of Gulf War Illnesses, the RAND Corporation released a report including an examination of DEET.
When discussing the potential health effects of DEET, the RAND reports states that DEET has been shown to affect the cardiovascular and nervous systems. The mechanism of cardiovascular toxicity has been investigated in experiments in rats and blood pressure changes have been found in dogs.
The RAND report also notes episodes of severe DEET toxicity in mammals are usually related to a direct action on the nervous system and that experimental animals that received very large doses of DEET have manifested coma and death.
The RAND report goes on to summarize 23 case reports of DEET exposure and possible toxicities. The report states the most reports of severe DEET adversity in humans describe neurologic symptoms, and most of the severe adverse reactions occur in children.
These reports sound dire, however, this is what a leading environmental group has to say about DEET.
The EWG states that DEET isn’t a perfect choice nor the only choice. But weighed against the consequences of Lyme disease and West Nile virus, we believe it is a reasonable one.
Among the four repellent chemicals EWG found to be top picks is DEET, which they say is better than many people assume. Its effectiveness at preventing bites is approached by only a few other repellent ingredients.
Bug Repellents recommended by the CDC and the EWG
- Oil of Lemon Eucalyptus and its synthetic derivative PMD
This seems to be the case of a lesser of two evils. The chemicals are most likely safe when use in low amounts and as directed. They are likely better than contracting Lyme Disease or the West Nile Virus.
- Other things you can do to prevent bug bites include wearing long sleeves, tuck pants into socks and use nets or fans over eating areas and strollers.
- Standing water around your home should be drained, especially if you live in an area with mosquitos and ticks.
HealthyChildren.org and the American Association of Pediatrics have several recommendations using repellents on children.
- Use as little possible to be effective.
- No more than 30% DEET.
- Insect repellents should not be used on children younger than 2 months.
- Permetrin should never be applied to the skin.
- Do not use products that combine DEET with sunscreen as this can lead to overexposure.
- Call the National Poison Control line immediately at 1-800-222-1222 if you suspect your child is having a reaction.
Given the unknowns and need for more evidence, we’ve chosen not to use chemical insect repellents frequently. However, sometimes during times of high risk exposure, deeper woods exploration, a small amount of DEET may be reasonable.
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In good health,
J Lee Jenkins, MD
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J Lee Jenkins, MD, MSc, FACEP is a practicing board-certified emergency physician and researcher in emergency public health. She can also be found on twitter (twitter.com/jleejenkins) and Facebook (J Lee Jenkins MD).
Information on this web site is provided for informational purposes only. This blog is not intended to provide personal medical advice. As always, please consult with your personal doctor prior to making any changes to your health regimen.