How to Use DEET on Skin, Clothing, and Kids Safely

DEET remains the most widely studied and broadly effective insect repellent available, and using it safely comes down to a few straightforward habits: apply it to exposed skin in the lowest concentration that covers the time you need, keep it away from wounds and eyes, and follow age-specific guidelines for children. The details behind those habits are worth knowing, because common mistakes with DEET tend to involve using too much, mixing it carelessly with sunscreen, or applying it to kids the same way you would to yourself.

How DEET Works and Why That Matters for Application

Understanding what DEET does at a basic level helps explain why the application rules exist. DEET does not kill insects. Instead, it interferes with how mosquitoes find you. Research shows it operates in at least two ways: it reduces the concentration of human odor molecules that evaporate from treated skin, and it directly disrupts the olfactory receptors mosquitoes use to home in on a host.¹ Separate work demonstrated that DEET blocks the electrical responses of mosquito smell neurons to attractive odors, essentially jamming the signal that tells a mosquito you are nearby.²

Because DEET works by creating a vapor barrier above your skin, it only protects the area where it has been applied. Miss a spot on your ankle, and mosquitoes will find it. This also means DEET needs to evaporate steadily to stay effective, which is why protection time is tied so closely to concentration and why reapplication matters once it wears off.

Concentration Controls Duration, Not Strength

One of the most common misconceptions about DEET is that a higher percentage means a more powerful repellent. In reality, concentration primarily determines how long the protection lasts, not how completely it blocks insects during that window. A product with about 24% DEET provided roughly five hours of complete mosquito protection in a controlled comparison study.³ Lower concentrations protect you just as well while they last, but they wear off sooner.

For a typical outing of a few hours, a product in the 20–30% range is usually plenty. Concentrations above 50% exist, but they add diminishing returns in protection time and increase the amount of chemical sitting on your skin. If you are going on a short walk in the backyard, something in the 10–15% range may be all you need. Match the concentration to the duration of your exposure, and you avoid applying more than necessary.

Applying DEET to Skin

The goal is a thin, even layer on exposed skin. Spray or rub it on like you would a light moisturizer. You do not need to drench yourself. Thick application does not improve protection; it just increases the amount your body absorbs without meaningful benefit. Studies on human volunteers found that when DEET was applied directly to skin, roughly 5–8% of the applied dose was absorbed through the skin and later recovered in urine.⁴ That absorption is low enough to be safe at normal use levels, but there is no reason to push it higher than needed.

A few practical rules help keep things clean:

Avoid broken skin: Do not apply over cuts, rashes, sunburns, or irritated areas. Damaged skin absorbs more of anything you put on it.
Skip your hands near your face: Apply DEET to your hands and then rub it onto your face sparingly, avoiding the eyes and mouth. Never spray DEET directly at your face.
Wash it off indoors: Once you are back inside and no longer need protection, wash treated skin with soap and water. Leaving it on overnight serves no purpose.

DEET can cause skin irritation in some people, and early toxicology reviews documented cases of dermatitis, including occasional blistering reactions in sensitive individuals.⁵ Lab testing on skin models has also shown that DEET can trigger inflammatory responses when applied heavily.⁶ If you notice redness or a rash after using a DEET product, wash it off and try a lower concentration or a different repellent next time.

Using DEET on Clothing

DEET can be sprayed on clothing, hats, and shoes for an extra layer of protection, and this is a useful strategy for covering areas you do not want to coat with repellent directly, like the skin under a collar or around your waistband. Spray the fabric lightly and let it dry before putting it on.

There are a couple of caveats. DEET can damage certain synthetic fabrics, plastics, and finished surfaces. Spandex, rayon, and some nylons can dissolve or become discolored. It can also ruin watch crystals, eyeglass lenses, and gear with plastic coatings. Cotton and most natural fibers tolerate it well. If you are wearing expensive technical gear, test a hidden spot first or use a permethrin-based clothing treatment instead.

That brings up an important comparison. For clothing-only protection against ticks specifically, permethrin tends to outperform DEET. A field study comparing treated military uniforms found that permethrin-treated clothing reduced tick encounters by about 97–98%, while DEET-treated clothing reduced them by about 60%.⁷ An earlier evaluation found a similar gap, with permethrin on clothing providing complete protection against all tick life stages while DEET sprayed on clothing delivered around 86–92% protection depending on concentration.⁸ The ideal approach in tick-heavy areas, and what the U.S. military has used for years, is to combine both: permethrin on clothing and DEET on exposed skin.⁹

DEET and Children

This is where people get the most anxious, and the anxiety is not entirely unfounded. A case review found 17 reports in the literature of DEET-associated encephalopathy (brain swelling and dysfunction) in children, with seizures being the most common symptom. These reactions occurred not only after ingestion or heavy repeated application, but in nearly half the cases after what was described as brief skin exposure, sometimes with products containing less than 20% DEET.¹⁰ The authors of that review concluded that DEET on children’s skin carries risk and should be avoided.

Regulatory agencies have taken a more measured stance. The general consensus from bodies like the EPA, Health Canada, and the American Academy of Pediatrics is that DEET can be used on children older than two months, but with specific precautions:

Use lower concentrations: Products with 10–30% DEET are the usual recommendation for children. Avoid the high-concentration formulas designed for all-day backcountry use.
Adults apply it: Never let a child apply their own repellent. Spray it onto your hands first and then rub it onto the child, avoiding the hands, eyes, and mouth.
Limit to exposed skin: Do not apply under clothing. Treat the child’s clothing instead when possible.
One application is usually enough: Avoid repeated reapplication on children unless the outing genuinely calls for it. The more applications in a day, the higher the cumulative dose.

The case reports that raised alarm involved unusual circumstances: ingestion by toddlers, application over large body areas multiple times a day, or use on very young infants. Used sparingly and applied by an adult to limited exposed skin, DEET’s decades-long safety record in children is considered acceptable by most public health agencies when weighed against the diseases mosquitoes carry.

Pregnancy and Breastfeeding

Pregnant and nursing women often avoid DEET out of caution, but the available evidence is reassuring. The largest study on this question was a randomized trial of nearly 900 pregnant women in Thailand who applied therapeutic doses of DEET daily during their second and third trimesters to help prevent malaria. No adverse neurological, gastrointestinal, or skin effects were observed in the mothers, and no effects on survival, growth, or development were detected in their babies at birth or at one year of age.¹¹ Animal studies similarly found no fetal malformations at any dose, with adverse effects appearing only at doses far beyond anything encountered in normal human use.

A clinical review in the BMJ concluded that DEET is safe for use from the second trimester onward and while breastfeeding.¹² If you are pregnant and traveling to an area with mosquito-borne disease, the risk of skipping repellent is real and quantifiable. The risk of using DEET at normal doses, based on the best available evidence, is not.

The Sunscreen Problem

Many people heading outdoors need both sun protection and insect protection, and the interaction between DEET and sunscreen is a genuine concern that does not get enough attention. A clinical trial found that sunscreen loses about a third of its sun protection factor when used together with DEET.¹³ So the SPF 30 on the bottle might behave more like SPF 20 in practice if you are also wearing DEET.

The interaction goes both ways. When DEET and oxybenzone (a common sunscreen ingredient) are applied together, each one drives more of the other through the skin. One study found that combined use increased the amount of DEET absorbed through the skin by roughly 36–108% compared to DEET alone.¹⁴ A follow-up using human urinary metabolites confirmed that applying sunscreen over DEET on the skin led to significantly higher DEET absorption, while applying DEET over sunscreen did not produce the same spike.¹⁵

The practical takeaway: apply sunscreen first and let it absorb for 15–20 minutes, then apply DEET on top. This order gives the sunscreen a chance to bind to your skin before the DEET layer goes on, and it avoids the worst of the absorption-enhancement effect. Avoid combination sunscreen-repellent products. They encourage reapplication at sunscreen intervals (every two hours), which means reapplying DEET far more often than necessary and increasing cumulative skin absorption for no insect-protection benefit.

When Mosquitoes Become Less Sensitive to DEET

A finding that surprised researchers is that mosquitoes can become temporarily less responsive to DEET after being exposed to it. In lab experiments with Aedes aegypti (the species that carries dengue and Zika), female mosquitoes that had already been exposed to DEET once were significantly more willing to land on and probe a DEET-treated arm during a second exposure, compared to mosquitoes encountering DEET for the first time.¹⁶ This does not mean DEET stops working; it means that individual mosquitoes that survive an encounter with DEET may be bolder on the next attempt. In a practical outdoor setting, where you are not dealing with the same mosquito twice in a controlled way, this is more a curiosity than a crisis. But it does reinforce the point that DEET is not a force field. Proper application and coverage still matter.

DEET and Your Pets

Dogs and cats are much more sensitive to DEET than humans. Pets that lick DEET off their fur or off your skin can develop toxicity symptoms including vomiting, tremors, lack of coordination, and hyperexcitability.¹⁷ At higher doses in laboratory settings, dogs experienced drops in blood pressure, slowed heart rate, and reduced cardiac output.¹⁸

Never apply human DEET products to your dog or cat. If your pet needs insect protection, use veterinary-approved products designed for their species. And be aware that a dog who likes to lick your arms or legs after you have applied DEET is getting an oral dose. Wash treated skin before extended cuddling with pets, or keep the DEET-treated areas away from them until you can wash up.

What Happens to DEET in the Environment

DEET enters waterways mainly through wastewater, since it washes off skin in the shower and out of treated clothing in the laundry. Environmental fate modeling predicts that most DEET released into the environment ends up in surface water, with a smaller fraction in soil. Measured concentrations of DEET in surface waters are hundreds to thousands of times lower than the levels shown to affect aquatic organisms in laboratory testing, which means the risk of ecological harm at current use levels is considered low.¹⁹ DEET is one of the most commonly detected organic contaminants in water surveys, but detection and harm are different things. Its environmental footprint is far less concerning than its ubiquity in water samples might suggest.

Newer Formulations That Last Longer and Absorb Less

One of the ongoing challenges with DEET is that it evaporates relatively quickly and absorbs through skin more than you would ideally want. Researchers have been working on controlled-release formulations, essentially tiny polymer capsules that hold DEET and release it slowly over time. These microcapsule systems have shown a slow, steady release of DEET while simultaneously reducing how much penetrates through the skin.²⁰

In one head-to-head comparison, a microcapsule formulation cut skin absorption of DEET by about 30% compared to a standard ethanol-based formula, while actually increasing the amount of DEET evaporating from the skin surface, which is what repels mosquitoes. The controlled-release version maintained effective evaporation rates for more than 48 hours, compared to less than 15 hours for the conventional formula.²¹ A separate study using DEET loaded into hydrogel microparticles found even more dramatic reductions in skin permeation, with the formulation allowing roughly 50 times less DEET to cross through skin over 24 hours compared to a plain DEET solution.²²

These technologies are not yet widespread in consumer products, but they represent the direction the field is heading. The ideal DEET product would keep the repellent vapor active above your skin for a long time while minimizing how much chemical actually enters your body. The gap between lab prototypes and pharmacy shelves is closing, and some newer commercial repellent formulations already incorporate microencapsulation principles to extend wear time without requiring higher DEET concentrations.