DEET, picaridin, and oil of lemon eucalyptus are the most effective repellents against biting gnats when applied to skin. But repellents are only one layer of defense. Fans, fine-mesh screening, and treated clothing can all reduce bites significantly, especially when combined.
Skin-Applied Repellents That Work Best
The EPA registers three main active ingredients for skin-applied insect repellents: DEET (found in over 500 products), picaridin (about 40 products), and IR3535 (about 45 products). All three repel biting gnats, also called no-see-ums or biting midges. DEET remains the most widely tested. A concentration of about 24% provides roughly five hours of protection per application. Lower concentrations still work but wear off sooner, so you’ll need to reapply more frequently.
Picaridin is a strong alternative if you dislike the feel or smell of DEET. It’s less greasy, doesn’t damage plastics or synthetic fabrics, and performs comparably in field tests against small biting flies. IR3535 tends to appear in milder, family-oriented formulations and works well for shorter exposure windows.
Oil of Lemon Eucalyptus as a Natural Option
Oil of lemon eucalyptus (OLE) is the standout plant-based repellent. In a field trial against biting midges in California’s Central Valley, researchers exposed ten subjects to gnats for six continuous hours while wearing either an OLE spray, an OLE lotion, a DEET control, or nothing. Half the subjects using the eucalyptus formulations received zero bites over the full six hours, and the researchers noted that the true median protection time likely exceeded the entire test duration. That puts OLE in the same ballpark as DEET for gnats specifically.
One important restriction: products containing OLE or its synthetic version (PMD) should not be used on children under 3 years old. For young kids, stick with DEET or picaridin and follow the label instructions. Apply repellent to your own hands first, then rub it onto your child’s exposed skin, avoiding the hands, eyes, mouth, and any broken skin.
Why Fans Are Surprisingly Effective
Biting gnats are weak fliers. Their top flight speed is roughly 1 to 1.5 miles per hour, which means even a gentle, steady breeze throws them off course. A portable fan on a low setting creates enough airflow to act as an invisible barrier around your patio, deck, or campsite. The moving air also disperses the carbon dioxide and body odors that gnats use to locate you, making it harder for them to find a target in the first place.
If you spend time outdoors in gnat-heavy areas, positioning a fan to blow across your seating area is one of the simplest and most reliable strategies available. It requires no chemicals and works continuously.
Candles vs. Diffusers for Area Protection
Citronella candles are a backyard staple, but the data on them is underwhelming. In controlled testing, citronella candles repelled only about 14% of biting insects indoors. Citronella diffusers performed much better at 68% indoors, but the real winner was geraniol. Geraniol candles repelled 50% of insects indoors, and geraniol diffusers hit 97% repellency.
Outdoors, effectiveness drops for all of them because wind disperses the active compounds. At about 20 feet from the source, citronella diffusers repelled just 22% of insects, while geraniol diffusers still managed 75%. The takeaway: if you’re buying area repellents, look for geraniol-based products and choose diffusers over candles. Diffusers release a steady concentration of the active ingredient, while candles burn through it inconsistently.
Fine-Mesh Screening Keeps Gnats Out
Standard window and porch screens have openings large enough for biting gnats to pass right through. To block them, you need 20×20 mesh screen, commonly sold as “no-see-um screen” or “tiny mesh.” This tighter weave prevents gnats, sand flies, and other micro-sized insects from getting through while still allowing reasonable airflow and visibility.
If you live in an area where gnats are a persistent problem, replacing porch or window screening with 20×20 mesh is one of the most effective long-term investments you can make. It’s particularly useful for screened porches, RV windows, and tent openings.
Permethrin-Treated Clothing
Permethrin is an insecticide you spray onto clothing, not skin. It works primarily through repellency rather than killing insects on contact. Research on factory-treated uniforms worn by outdoor workers in North Carolina found that even after three months of wear, treated clothing still deterred mosquitoes from biting, though the lethal effect on insects faded significantly over time. Workers wearing treated clothing showed lower immune responses to insect saliva proteins, confirming they were getting bitten less often.
You can buy pre-treated clothing or spray your own gear with a permethrin aerosol. Self-applied treatments need reapplication after several washes, and adherence tends to be poor because people forget or skip it. Pre-treated garments hold up longer but cost more. For gnats specifically, long sleeves and pants treated with permethrin give you a physical and chemical barrier in one layer.
Timing Your Outdoor Activities
Biting gnats and their relatives tend to be most active during specific windows of the day. Research on biting flies in Queensland found that different species peak at different times, with some most active in late morning, others in early afternoon, and still others in the late afternoon and evening. In areas with multiple species present, overlapping activity periods can create a high-bite-risk window stretching from mid-morning through early evening. Only extreme weather conditions, like heavy wind or rain, suppress activity across all species simultaneously.
Dawn and dusk are classic peak times for many gnat species in North America. If you can schedule outdoor time during the middle of a windy day, you’ll encounter fewer biting insects. When that’s not possible, layering repellent with a fan or treated clothing makes the biggest difference.
What About Skin So Soft?
Avon’s Skin So Soft bath oil has a devoted following as a gnat repellent, and it does have some basis in reality. Testing published in the Journal of the American Mosquito Control Association found it offered over 70% protection against midges (the same family as biting gnats). That said, it was still less effective than DEET, and the protection only lasted a few hours before needing reapplication. Some users extend its effectiveness by mixing a capful of rubbing alcohol into the spray bottle, though this is anecdotal rather than lab-tested. It’s a reasonable option for mild exposure but not a substitute for EPA-registered repellents during heavy gnat activity.