DEET is not bad for you when used as directed on skin. After more than 60 years on the market and use by an estimated 50 to 100 million Americans each year, the EPA concluded that insect repellents containing DEET “do not present a health concern” to the general population, including children. That said, there are real nuances worth understanding, especially around how much gets absorbed, how it works, and a few situations where you should be more careful.
How DEET Actually Works
DEET doesn’t kill mosquitoes. It repels them by activating a specific smell receptor on the insect’s antennae. Researchers identified this receptor, called OR136, in the southern house mosquito and showed that knocking it out completely eliminated DEET’s repellent effect. In simple terms, DEET creates a scent signal that mosquitoes find overwhelming or confusing, so they stay away. It doesn’t need to interact with your biology to do its job.
What Happens When DEET Touches Your Skin
A small fraction of the DEET you apply does get absorbed into your body. According to the Agency for Toxic Substances and Disease Registry, less than 10 to 20% of applied DEET penetrates the skin. Your body processes it relatively quickly and excretes most of it through urine.
One important factor: sunscreen can significantly increase absorption. In a study using a hairless mouse skin model, a commercially marketed sunscreen-DEET combo with only 10% DEET was detected in the bloodstream six times faster than a plain 20% DEET product, and ultimately delivered 3.4 times more DEET into the body at steady state. If you need both sun protection and insect repellent, apply sunscreen first, let it absorb, then apply DEET on top. Avoid combination sunscreen-repellent products, since sunscreen needs reapplication far more often than repellent, which could lead to excessive DEET exposure.
The Neurotoxicity Question
You may have seen claims that DEET inhibits a key brain enzyme called acetylcholinesterase, the same target that nerve agents attack. A 2014 study in PLOS ONE tested this directly and found that DEET is a very weak inhibitor of human acetylcholinesterase, requiring concentrations in the millimolar range to have any effect. The researchers concluded that this mechanism is “unlikely to cause toxicity” in humans at real-world exposure levels.
DEET can block sodium and potassium channels in nerve cells at high concentrations in lab settings. This probably explains the numbing sensation you get if DEET accidentally touches your lips or mouth. But those concentrations are far above what normal skin application produces in the bloodstream. In insects, DEET appears to work through a completely different nerve signaling system (octopamine) that mammals don’t rely on in the same way.
Reported Serious Reactions
Since DEET entered the U.S. market in 1956, a small number of serious reactions have been documented. A CDC report identified six cases of toxic systemic reactions in girls aged 17 months to 8 years after repeated skin application. These children developed behavioral changes, loss of coordination, seizures, or coma, and three died. Another six toxic reactions followed ingestion of DEET.
Those numbers need context. With 50 to 100 million people using DEET every year for decades, a handful of cases represents an extraordinarily rare event. When five seizure cases in New York were investigated in 1989, the CDC noted that none were “clearly established as DEET toxicity” and that with so many people using the product, some temporal associations with seizures would be expected by chance alone. The pattern in the pediatric cases involved repeated, heavy application, not typical single-use scenarios.
Safety for Children and Pregnant Women
The EPA approves DEET for use on children with no age restriction and no cap on concentration. The CDC echoes this, stating that DEET, picaridin, IR3535, and 2-undecanone can all be used on children without age restriction. The key precautions for kids are practical: don’t apply it to their hands (they touch their eyes and mouths), don’t let young children apply it themselves, and wash it off when they come inside.
For pregnancy, the UK Teratology Information Service reviewed the available human data and found no evidence of adverse fetal effects from DEET use, though the data are limited. Their conclusion is that the benefits of preventing insect-borne diseases like malaria clearly outweigh any theoretical risk. This is particularly relevant for pregnant travelers to areas where mosquito-borne illness is common.
Higher Concentration Means Longer Protection, Not Stronger
A common misconception is that a higher DEET percentage gives you “more” protection. It doesn’t. Higher concentrations last longer, but a 100% DEET product doesn’t repel mosquitoes any more effectively than a 30% product in the moment. The difference is entirely about duration:
- 6.65% DEET: roughly 2 hours of protection
- 20% DEET: almost 4 hours
- 23.8% DEET: about 5 hours
Above 50%, there’s no additional increase in protection time. For most outdoor activities, a product in the 20 to 30% range covers you for a full afternoon. If you’re doing yard work for an hour, something in the single digits is fine. Choosing the lowest concentration that matches your time outdoors is a sensible way to minimize unnecessary exposure.
Practical Ways to Reduce Exposure
The EPA label requirements for DEET products reflect the simplest ways to stay safe. Apply it only to exposed skin or clothing, not underneath clothing where it can’t evaporate and stays in prolonged contact with skin. Don’t apply over cuts or irritated skin, which increases absorption. Spray your hands first and rub it on your face rather than spraying directly. When you come indoors, wash treated skin with soap and water, and wash treated clothing before wearing it again.
Avoid using DEET in enclosed spaces, and don’t overapply. A thin, even layer does the job. Soaking your skin doesn’t improve protection but does increase absorption for no benefit. In rare cases, DEET can cause skin irritation, so if you notice a rash, wash it off and try a lower concentration or an alternative repellent like picaridin.