Gnat Repellent: What "Gnats" Actually Are and How to Pick One
The biting "gnats" that swarm your yard are usually biting midges, which Illinois DPH says are also called punkies, no-see-ums or simply gnats. IL DPH names DEET and picaridin as the actives to look for, and the CDC adds two force multipliers: 20x20 mesh screens and an outdoor fan.
"Gnat" is not a species. It is the word people reach for when something small and infuriating is orbiting their head, and it covers several different insects. Which one you have determines what works, so start there.
What are the gnats that are biting me?
If they bite, they are most likely biting midges. The Illinois Department of Public Health puts it plainly: biting midges "are also known as 'punkies,' 'no-see-ums' or simply 'gnats,'" and they are so small, no more than 1/32 of an inch, that "their tiny size allows them to penetrate window and door screens." They are serious pests along the shores of oceans, lakes, ponds and rivers, and will bite during the day or at night.
The other biter that carries the name: black flies, which Illinois DPH notes are also called "buffalo gnats." They are bigger, up to 1/8 inch with a humpbacked look, and they live near creeks and rivers. If your gnats appeared in late spring near running water and the bites bleed, read our black fly guide instead; this page is for the tiny shoreline swarmers.
What repellent works on biting gnats?
Two answers, one from each agency lane.
On actives, Illinois DPH: repellents "containing the active ingredient DEET (N,N-diethyl-meta-toluamide) or picaridin are best," with the honest caveat that repellents, while effective against mosquitoes, "have been found to be less effective against some types of biting flies," so they should be supplemented with other measures: avoiding the areas the flies inhabit, avoiding peak biting times, and wearing heavy-duty, light-colored clothing with long sleeves, long pants and hats.
On labels, the CDC's guidance for biting midges: "Look for EPA-registered repellents labeled for flies, biting flies, or Culicoides (biting midges, punkies, granny nippers, and no-see-ums)." The CDC also notes that when used as directed, EPA-registered insect repellents are proven safe and effective. A midge claim is registered pest by pest, so the product's own federal label is where the answer lives, and EPA's rule applies: always read the product label before using the product.
We read those labels so you do not have to squint at 631 of them. The Repellent Index holds every EPA-registered skin-applied repellent with the pest claims on each product's federal label: 111 of the 631 carry a stated gnat protection time, and 47 a no-see-um time. The statistics and dataset are free.
One more reading tip for the shelf: the phrasing on labels varies. The CDC's list of words to look for runs from the plain (flies, biting flies) to the taxonomic (Culicoides) to the regional nicknames (biting midges, punkies, granny nippers, no-see-ums). Any of those on a federal label is the claim you are looking for. None of them is implied by the word "mosquitoes."
How do you apply it so it holds up?
EPA's application rules, short version: read and follow the label directions and understand how much to apply; apply only to exposed skin and/or clothing, never under clothing. Gnat swarms go for any skin you left bare, so coverage of exposed skin matters more than a thick coat in one spot.
What clears gnats out of a yard or porch?
Two cheap physical tools, both agency-backed:
- A fan. The CDC recommends using fans outdoors to help blow biting midges away, and Illinois DPH agrees: fans can keep small areas free of flies, "especially smaller flies whose flight is affected by air currents." Gnats are weak fliers. A box fan on the porch beats most gadgets sold for this job.
- Finer screens. The CDC notes that many commonly used window and door screens do not have holes small enough to stop biting midges, and recommends looking for mesh screens measuring 20x20. If gnats show up inside a screened porch, the screen is the reason.
Add the Illinois DPH basics, and the picture is complete: avoid the shoreline hours when the swarm is thickest, and put fabric between them and you. The department's clothing prescription for biting flies generally is heavy-duty and light-colored, long sleeves, long pants and hats, and it applies here for the simplest reason: skin that is covered does not need defending.
What does not earn a place in the plan: anything that promises to clear a whole yard of gnats from a single point. The insects breeding along a shoreline are a population, not a visitor, and the agency guidance above never mentions a zapper or a sonic device. Moving air, finer mesh, covered skin and a labeled repellent are the tools with public health guidance behind them.
Longsleeve is an EPA-registered picaridin lotion (EPA Reg. No. 101457-1). It repels mosquitoes and ticks for up to 14 hours, and its accepted federal label carries the claim "Repels biting flies, stable flies, black flies, gnats, chiggers, sand flies and Scottish biting midges (no see-ums) for up to 8 hours." It is fragrance-free, with nine disclosed ingredients.
Short answers
What is the best gnat repellent?
No agency ranks products. Illinois DPH names DEET and picaridin as the actives to look for against biting flies, and the CDC says to pick an EPA-registered repellent whose label lists flies, biting flies, or Culicoides. 111 of the 631 registered skin repellents carry a stated gnat protection time on their federal label.
Why do gnats get through my window screens?
Illinois DPH: their tiny size, no more than 1/32 of an inch, lets them penetrate window and door screens. The CDC's fix is 20x20 mesh.
Does a fan really keep gnats away?
Yes, and it is the cheapest tool on this page. The CDC recommends fans outdoors to blow biting midges away; Illinois DPH notes fans keep small areas free of smaller flies because their flight is affected by air currents.
Do gnats bite during the day?
Biting midges will bite during the day or at night, per Illinois DPH, and they are at their worst along shorelines. Timing your porch hours around them is harder than it is for dusk-biting mosquitoes, which is why the fan and the screens do so much of the work.
Are gnats and no-see-ums the same thing?
Often, yes. Illinois DPH lists punkies, no-see-ums and gnats as names for the same biting midges. The exception is "buffalo gnats," which are black flies, a different insect with different habits.
Sources
- Illinois Department of Public Health, Biting Flies. https://dph.illinois.gov/topics-services/environmental-health-protection/structural-pest-control/biting-flies.html
- CDC, Preventing Oropouche. https://www.cdc.gov/oropouche/prevention/index.html
- EPA, Using Insect Repellents Safely and Effectively. https://www.epa.gov/insect-repellents/using-insect-repellents-safely-and-effectively
Last reviewed 2026-08-26 · every claim on this page is sourced above