DEET is the most effective and well-studied insect repellent available, providing hours of protection against mosquitoes, ticks, biting flies, fleas, and chiggers. Using it correctly comes down to choosing the right concentration for your situation, applying it properly to exposed skin, and washing it off when you’re back indoors.
Choose a Concentration Based on Time Outdoors
DEET concentrations range from about 5% to 100%, but higher percentages don’t repel insects more effectively. They simply last longer. A product with around 10% DEET protects for roughly two hours. A concentration around 24% provides about five hours of complete protection. Anything above 30% adds diminishing returns in duration without meaningful extra benefit for most outdoor activities.
If you’re doing yard work for an hour, a 10% product is plenty. For a full day of hiking or camping, something in the 20% to 30% range keeps you covered without reapplying constantly. Products near 100% DEET exist, but most people never need them. Match the concentration to how long you’ll actually be outside.
How to Apply DEET Correctly
Use just enough to cover your exposed skin. A thin, even layer works as well as a heavy coating, and applying more doesn’t boost effectiveness. If you’re using a spray, do it outdoors or in a well-ventilated area to avoid breathing it in.
Never spray DEET directly onto your face. Instead, spray it onto your hands first, then rub it across your forehead, cheeks, and neck while avoiding your eyes and mouth. Skip any cuts, scrapes, or irritated patches of skin. You can also apply it to the outside of clothing for extra coverage, but keep it off skin that’s already covered by fabric since that’s unnecessary.
For children, parents should handle the application themselves. Don’t put DEET on a child’s hands, because kids touch their eyes and mouths frequently. Apply it to their exposed arms, legs, and neck, and let an adult handle the face application with the hands-first method.
Using DEET With Sunscreen
When you need both sun protection and bug protection, apply sunscreen first and let it absorb into your skin, then apply DEET on top. Research published in the Journal of the American Academy of Dermatology found that DEET works just as well when layered over sunscreen. However, sunscreen loses about a third of its SPF when paired with DEET, so consider using a higher SPF than you normally would, or reapply sunscreen more often.
Avoid combination sunscreen-repellent products. Sunscreen needs reapplication every two hours, while DEET lasts much longer. Using a combo product means you’ll either reapply DEET too frequently or not reapply sunscreen enough.
What DEET Can Damage
DEET is a plasticizer, which means it can dissolve or warp certain materials on contact. Watch out for synthetic fabrics like spandex and rayon, as well as rubber, vinyl, and elastic. It can also damage eyeglass frames and lenses, watch faces, contact lenses, combs, and painted or varnished surfaces. If you’re wearing gear you care about, apply DEET to your skin rather than spraying it over equipment. Cotton, wool, and nylon generally hold up fine.
Washing DEET Off
Once you head indoors and no longer need protection, wash treated skin with mild soap and water. This is straightforward but worth making a habit, especially before eating or touching your face. If you applied DEET to clothing, wash those items before wearing them again. If you notice a rash, itching, or swelling at any point, wash the product off immediately and stop using it.
Safety for Children, Pregnancy, and Breastfeeding
The EPA approves DEET for use on children with no age restriction and no limit on concentration. Testing has shown no difference in effects between young and adult animals, which is the basis for that approval. That said, many pediatricians suggest using lower concentrations (10% to 30%) for kids simply because they don’t need eight hours of protection for a typical afternoon outside.
Both the CDC and the EPA consider DEET safe and effective during pregnancy and breastfeeding when used as directed. In areas where mosquito-borne illnesses like Zika or West Nile virus are a concern, the risk of skipping repellent is far greater than the risk of using it. Breastfeeding mothers should avoid applying DEET directly to the breast or any area where an infant’s mouth might contact the skin.
Why Wristbands and Partial Application Don’t Work
DEET only protects skin within about 4 centimeters of where it’s applied. A study in the New England Journal of Medicine tested wristbands impregnated with DEET and found they provided no meaningful protection against mosquito bites on the rest of the body. The same was true for citronella wristbands. If a mosquito can reach untreated skin, it will bite there. Full coverage of exposed areas is what makes DEET effective.