The most effective mosquito and tick sprays contain one of four EPA-registered active ingredients: DEET, picaridin, IR3535, or oil of lemon eucalyptus. Products with 20% or higher concentrations of these ingredients provide several hours of protection against both mosquitoes and ticks, while lower-concentration formulas (under 10%) may only last one to two hours. Choosing the right spray depends on how long you’ll be outdoors, who’s using it, and what pests you’re most concerned about.
How Repellent Sprays Actually Work
Mosquitoes and ticks find you by detecting chemicals your body releases, particularly compounds in your breath, sweat, and skin. Repellent sprays don’t kill these insects. Instead, they scramble the signals mosquitoes and ticks use to locate you. DEET works by both triggering and blocking smell receptors on mosquitoes, essentially overloading their sensory system with confusing input. Picaridin and IR3535 take a slightly different approach, shutting down the receptor machinery more broadly so mosquitoes can’t process the human odors that normally draw them in.
The result is the same for all of them: insects can’t accurately sense you as a host, so they move on. This is why repellents work best when applied evenly across exposed skin. A missed patch of ankle or forearm is still fully detectable to a hungry mosquito.
Comparing the Four Main Active Ingredients
All four EPA-registered ingredients are effective, but they differ in protection time, feel on the skin, and who can safely use them.
- DEET is the most studied repellent ingredient available. At 5% concentration it lasts about 2 hours, at 15% about 6 hours, and at 30 to 50% around 8 hours. Going above 50% offers no additional benefit. DEET can damage some plastics and synthetic fabrics, and some people dislike its oily feel.
- Picaridin is a synthetic compound inspired by a molecule found in black pepper. It performs comparably to DEET without the greasy texture or damage to gear. Concentrations up to 20% are effective, with no added benefit beyond that.
- IR3535 is a synthetic version of a naturally occurring amino acid. It’s widely used in Europe and is gentle on skin, though it tends to offer shorter protection windows similar to lower-concentration DEET products.
- Oil of lemon eucalyptus (OLE) is the one plant-derived option with EPA registration. At around 40% concentration, it performs about as well as 20% DEET against mosquitoes. It cannot be used on children under 3 years old. OLE is not the same thing as pure lemon eucalyptus essential oil, which is not recommended as a repellent.
Higher concentrations extend how long a repellent works, but they don’t repel insects any more effectively during that time. A 50% DEET spray isn’t “stronger” than a 20% spray. It just lasts longer before you need to reapply.
Permethrin for Clothing and Gear
Permethrin is a separate category entirely. Unlike skin-applied repellents, permethrin is sprayed onto clothing, boots, tents, and other gear. It kills ticks and mosquitoes on contact rather than simply repelling them. You can treat items yourself with 0.5% permethrin spray, or buy pre-treated clothing that lasts through multiple washes.
When applying permethrin at home, spray garments outdoors in a ventilated area, then hang them to dry completely before wearing. Never apply it to clothing while you’re wearing it, and never put it directly on skin. Once dry, permethrin binds tightly to fabric, so very little transfers to your body during wear. Wash treated clothing separately from untreated items.
Pairing permethrin-treated clothing with a skin repellent like DEET or picaridin creates a two-layer defense that is especially valuable in areas with high tick activity or disease risk.
Protection for Children
Babies under 2 months old should not have any DEET-based repellent applied to their skin. For infants over 2 months and older children, DEET concentrations up to 30% are considered safe when used as directed. Picaridin is also an option for young children and tends to be less irritating.
Oil of lemon eucalyptus has a firm age cutoff: do not use it on children under 3. For toddlers and babies, covering strollers and carriers with mosquito netting is a practical alternative that avoids repellent application altogether. When you do apply repellent to a child, put it on your own hands first and then rub it onto their skin, avoiding the hands, eyes, and mouth.
Using Repellent During Pregnancy
DEET has the most safety data during pregnancy. Animal studies using doses far higher than normal human exposure found no increased risk of birth defects, and a human study covering the second and third trimesters showed no adverse outcomes. No first-trimester human data has been published, but major health agencies still recommend DEET as a first-line option for pregnant women because the diseases mosquitoes and ticks carry pose a greater risk than the repellent itself.
Picaridin has shown no harmful effects in animal reproductive studies, though human data during pregnancy is limited. OLE and IR3535 lack pregnancy-specific research, making them less ideal choices when other well-studied options are available. Permethrin-treated clothing is considered very low risk during pregnancy because absorption through skin from treated fabric is negligible.
For breastfeeding, DEET is absorbed through the skin in small amounts but becomes undetectable in the blood within about 4 hours of application. Avoiding breastfeeding during that window and keeping repellent residue away from the breast area minimizes any potential transfer.
Why Combination Sunscreen Products Fall Short
Products that combine sunscreen and insect repellent in a single bottle seem convenient, but they create a timing problem. Sunscreen needs reapplication every two hours, while most repellents last much longer. Reapplying the combo product on a sunscreen schedule means layering on far more repellent than you need. Insect repellent also shouldn’t go on the face, while sunscreen should.
The CDC recommends using two separate products. Apply sunscreen first, wait about ten minutes for it to absorb, then apply your repellent on top. Some repellent ingredients can reduce sunscreen effectiveness when mixed directly, so keeping them separate ensures both work as intended.
Essential Oil Sprays and Other “Natural” Options
Products containing citronella, peppermint, rosemary, or other essential oils are widely marketed as natural alternatives. Most of these are not EPA-registered, which means they haven’t been required to prove they actually work against mosquitoes or ticks before making claims on their label. In practice, essential oil sprays typically provide 20 minutes to an hour of partial protection, far short of what registered ingredients deliver.
If you’re in an area where mosquitoes or ticks carry disease (Lyme disease, West Nile virus, Rocky Mountain spotted fever), essential oil sprays are not a reliable substitute for EPA-registered repellents. They may be adequate for a short backyard dinner where disease risk is low, but they’re not appropriate for hiking in tick-heavy woods or traveling to regions with mosquito-borne illness.
Keeping Pets Safe Around Repellents
DEET can cause skin irritation in dogs even at low concentrations, and repeated exposure can build up in their skin. If a dog chews on a DEET canister or gets heavily sprayed, more serious symptoms like vomiting, tremors, or seizures are possible.
Permethrin is the bigger concern for pet households. While some flea and tick products for dogs contain permethrin, it is extremely toxic to cats. Even indirect exposure, such as a cat grooming a dog that was recently treated with a permethrin product, can cause severe neurological symptoms including seizures and potentially death. If you have cats, keep permethrin-treated clothing stored away from them and never let a cat come into prolonged contact with freshly treated fabric or a recently treated dog.