DEET is the most thoroughly tested mosquito repellent available, with over 60 years of use and strong evidence behind it. But “best” depends on what you need. For sheer duration of protection against the widest range of mosquito species, DEET at 20% concentration or higher is hard to beat. Other repellents, particularly picaridin and oil of lemon eucalyptus, perform comparably in many situations and come with fewer downsides.
How DEET Actually Works
DEET doesn’t kill mosquitoes. It scrambles their ability to find you. Mosquitoes locate humans primarily through smell, detecting carbon dioxide and body odors from dozens of feet away. DEET interferes with their olfactory receptor cells, essentially confusing the insect so it can’t zero in on your skin. Research from the USDA has also found that DEET activates a bitter taste receptor in mosquitoes, similar to the one triggered by quinine. This means even if a mosquito lands on treated skin, it gets a chemical signal that discourages it from biting.
How Long DEET Protection Lasts
The concentration of DEET in a product determines how long it works, not how strongly it repels. A 10% DEET formula provides about 2 hours of protection. A 30% formula extends that to roughly 5 hours. Going above 50% doesn’t add any extra benefit, so products with 98% or 100% DEET aren’t giving you more protection, just more chemical on your skin.
The CDC recommends using products with at least 20% DEET for meaningful outdoor protection. Standard ethanol-based DEET sprays typically last 4 to 8 hours, though newer controlled-release formulations use microcapsule technology to slow absorption into the skin and extend that window. If you’re spending an afternoon in the backyard, 20% to 30% DEET is plenty. For all-day hikes or travel in tropical regions, 30% hits the sweet spot between duration and practicality.
How DEET Compares to Other Repellents
Three alternatives are worth comparing directly: picaridin, oil of lemon eucalyptus (OLE), and IR3535.
- Picaridin is the closest synthetic rival. A large review of repellent studies found that picaridin at 20% provides protection comparable to DEET against most mosquito species, lasting roughly 4 to 10 hours depending on the species. It’s odorless, doesn’t feel greasy, and won’t damage plastics or fabrics. For most everyday use, picaridin and DEET are functionally interchangeable.
- Oil of lemon eucalyptus (OLE) is the strongest plant-based option. Products with 30% to 40% OLE provide up to 6 hours of protection, matching or slightly exceeding 30% DEET in some tests. At lower concentrations (8% to 10%), it covers about 2 hours, similar to 10% DEET. One important limitation: the CDC says OLE should not be used on children under 3 years old.
- IR3535 is a synthetic amino acid derivative common in European products. It offers solid protection against most mosquitoes but generally falls slightly short of DEET and picaridin in head-to-head duration tests.
Not All Mosquitoes Are Equally Affected
DEET’s performance varies depending on the mosquito species, which matters if you’re traveling to areas with specific disease risks. Against Aedes mosquitoes (the species that carries dengue, Zika, and yellow fever), DEET at 20% or more showed the strongest efficacy in a large review, providing up to 10 hours of protection. Against Anopheles mosquitoes, which transmit malaria, all four major repellents (DEET, picaridin, OLE, and IR3535) performed similarly, offering 4 to 10 hours of protection on average. Culex mosquitoes, which can carry West Nile virus, are the easiest to repel, and all tested repellents worked well against them.
If you’re heading somewhere with a high risk of Aedes-borne diseases, DEET has the strongest evidence base for that specific genus. For general mosquito protection in North America or Europe, picaridin is equally effective.
Safety at a Glance
DEET has been used billions of times since its development in the 1950s, and serious adverse events are rare. The Agency for Toxic Substances and Disease Registry notes that given the many millions of DEET applications per year in the United States, reports of serious health effects have been limited. Earlier concerns about seizures in children have largely been attributed to statistical coincidence: since 23% to 29% of U.S. children are exposed to DEET and seizure disorders occur in 3% to 5% of children from any cause, some overlap is expected by chance alone.
EPA-registered repellents, including DEET, are considered safe for pregnant and breastfeeding women when used as directed. For children, the main precautions are straightforward: don’t apply repellent to a child’s hands, eyes, mouth, or broken skin. Adults should spray repellent onto their own hands first, then apply it to a child’s face.
The Practical Downsides of DEET
Where DEET loses points is usability. It has a distinctive chemical smell that many people find unpleasant. It feels oily on skin. And it can damage plastics, rayon, and spandex on contact, meaning it can ruin sunglasses, watch crystals, phone cases, and certain athletic clothing. If you’re wearing synthetic gear or handling equipment, this is a real consideration.
Picaridin avoids all of these problems. It’s nearly odorless, dries clean, and is safe on all fabrics and materials. OLE has a mild eucalyptus scent that most people find pleasant but needs to be reapplied more frequently at lower concentrations.
Choosing the Right Repellent for Your Situation
For most people on a typical summer evening, 20% picaridin or 20% to 30% DEET will provide the same practical result. The choice comes down to preference. If you dislike the feel and smell of DEET or you’re worried about your gear, picaridin is the better pick. If you’re traveling to a tropical area with high Aedes mosquito activity, DEET at 30% gives you the deepest evidence base and longest proven protection window against that specific threat.
For those who prefer plant-based options, 30% to 40% oil of lemon eucalyptus is a legitimate choice that holds up well in testing. Products with lower concentrations of any active ingredient, whether DEET, picaridin, or OLE, tend to top out at 1 to 2 hours of protection, which means frequent reapplication and a higher chance of gaps in coverage. Citronella candles, wristbands, and ultrasonic devices consistently fail in controlled tests and aren’t worth relying on when mosquito-borne disease is a concern.