The best gnat repellent depends on which type of gnat you’re dealing with. For biting gnats like no-see-ums and black flies, DEET and picaridin are the most effective options. For fungus gnats buzzing around your houseplants, the solution isn’t a repellent at all but a soil treatment that kills larvae at the source. Here’s what works for each situation and how to use it.
Biting Gnats vs. Non-Biting Gnats
The word “gnat” covers several very different insects, and the right approach changes depending on which one is bothering you. Biting midges (also called no-see-ums or punkies) and black flies are the two main outdoor biters. Black flies are small, dark, humpbacked flies that bite aggressively in spring and early summer. Biting midges are even tinier and often attack near water at dawn and dusk.
Then there are non-biting gnats. Eye gnats, common in the southeastern U.S., are only about 1.5 to 2 millimeters long and swarm around your face because they’re attracted to moisture from your eyes, nose, and ears. They don’t bite, but they’re maddening. Fungus gnats are the small flies you see hovering around potted plants indoors. They breed in moist soil and don’t bite either.
One important clarification from University of Georgia entomologists: biting midges and biting gnats do not enter homes. If you’re getting bitten indoors, the culprit is almost certainly mosquitoes, not gnats.
Best Repellents for Biting Gnats
EPA-registered repellents containing DEET or picaridin are the most reliable protection against biting gnats outdoors. Both active ingredients have been tested specifically against biting midges and black flies, and both work well.
DEET has the longest track record. Products with higher concentrations last longer, though there’s a ceiling to the benefit. Concentrations up to 30% are considered the recommended upper limit. A 20-30% DEET product will give you several hours of protection against no-see-ums and black flies, while a 10% product wears off faster and needs reapplication.
Picaridin is a newer alternative that performs comparably. At lower concentrations, it protects against mosquitoes, biting flies, and chiggers. Higher-concentration formulas (typically 20%) add tick protection to the label. Many people prefer picaridin because it feels less greasy and doesn’t damage plastics or synthetic fabrics the way DEET can.
Short-acting natural repellents like those containing citronella oil or lemon eucalyptus oil provide some protection, but they wear off much faster and require frequent reapplication. If you’re in an area with heavy gnat pressure, DEET or picaridin will outperform them significantly.
What Works Against Eye Gnats
Eye gnats are a frustrating exception. According to University of Georgia entomologists, there is no guaranteed way to keep eye gnats away from you besides strong breezes. Standard insect repellents offer limited help because these flies aren’t landing to bite. They’re hovering around your face to feed on moisture. A portable fan on a patio or porch is often more effective than any spray. Wearing a hat with fine mesh netting can also help if you’re working outdoors in areas where eye gnats swarm.
Getting Rid of Fungus Gnats Indoors
If your gnat problem is inside your home, you’re almost certainly dealing with fungus gnats breeding in the moist soil of houseplants. Repellent sprays won’t solve this because the gnats keep reproducing in the soil. The adults you see flying around are just the visible tip of the problem. The real target is the larvae living in the top inch or two of potting mix.
Reduce Soil Moisture
Fungus gnat larvae need consistently damp soil to survive. Letting the top layer of soil dry out between waterings is the simplest first step and often enough to break the breeding cycle on its own. Switching to bottom-watering (placing pots in a tray of water and letting the soil absorb moisture from below) keeps the surface drier while still hydrating roots.
Biological Soil Treatments
For a heavier infestation, parasitic nematodes are one of the most effective biological controls. The species Steinernema feltiae targets fungus gnat larvae specifically. These microscopic roundworms are mixed with water and poured into the soil, where they enter the larvae through natural body openings and release bacteria that kill them within three to four days. You can buy nematodes online and apply them at home.
Bacillus thuringiensis israelensis (Bti), the same bacterium used in mosquito dunks, also kills fungus gnat larvae when applied as a soil drench. However, formulations designed specifically for fungus gnats are mostly sold for commercial greenhouse use and can be hard to find at retail stores. Mosquito dunks containing Bti can be crumbled into watering cans as a workaround, though this is an off-label use.
Contact Sprays and Sticky Traps
Sprays containing pyrethrins, insecticidal soap, neem oil, or horticultural oils can kill adult fungus gnats on contact, but they don’t persist long enough to provide real control. You’d need to reapply every couple of days, which gets tedious and still doesn’t address the larvae in the soil. Yellow sticky traps placed near plants catch adults and help you monitor how bad the infestation is, but they won’t eliminate it alone. Think of traps as a useful supplement to soil treatments, not a standalone solution.
Using Repellents Safely on Children
The American Academy of Pediatrics recommends against using any insect repellent on children younger than two months old. For babies that young, clothing and mosquito netting are the only safe options. For children older than two months, DEET-based products are considered safe, but the AAP recommends keeping concentrations at 30% or below.
Product labels sometimes list a minimum age for use. If no age restriction appears on the label, it means the EPA hasn’t placed one, not necessarily that it’s appropriate for all ages. A few practical precautions make a real difference with kids: don’t let them handle or apply the product themselves, avoid spraying near their eyes and mouth, and skip their hands entirely since children tend to put their fingers in their mouths. Spray the repellent on your own hands first, then rub it lightly onto their face and ears. Wash treated skin off as soon as they come inside.
Other Ways to Reduce Gnat Exposure
Repellents work best as part of a broader strategy. For outdoor biting gnats, timing matters. Black flies are most active during the day in late spring, while no-see-ums tend to peak around dawn and dusk. Avoiding outdoor activity during peak times reduces exposure significantly.
Wearing light-colored, long-sleeved clothing helps because dark colors attract many biting fly species. Permethrin-treated clothing adds another layer of protection. Unlike skin-applied repellents that wear off, permethrin binds to fabric fibers and remains effective through multiple washes. You can buy pre-treated clothing or spray your own gear with permethrin products designed for textiles.
Fans are underrated. Gnats are weak fliers, and even a moderate breeze makes it difficult for them to land. A box fan or oscillating fan on a porch or patio can create a gnat-free zone more reliably than candles or area repellent devices.