The best bug spray for no-see-ums uses an active ingredient the CDC lists for mosquito repellents, such as DEET, picaridin, PMD or oil of lemon eucalyptus, applied to every patch of exposed skin before dusk, especially ankles, feet, neck and hairline. Add a fan. Published field studies show DEET, PMD and lemon eucalyptus repellents holding up against biting midges.
The longer answer is about getting your evenings back: the sunset on the dock, the last swim of the day, dinner on a screened porch in Florida or Costa Rica. No-see-ums show up right when the light gets good. Here is how to stay out for all of it.
What are no-see-ums?
No-see-ums are biting midges in the genus Culicoides, part of the family Ceratopogonidae. According to University of Florida entomologists, there are over 4,000 species of biting midges worldwide, over 1,000 of them in Culicoides, and 47 species occur in Florida alone. The adults are gray and less than 1/8 inch long.
That size explains the name. UF/IFAS Extension describes the classic experience: something is clearly biting you, but you cannot see what it is. If you are trying to work out what bit you, our guide to no-see-um bites shows what they look like and how they compare with mosquito and bed bug bites.
Are they sand flies? Many people search for "bug spray for sand flies" when they mean no-see-ums. UF/IFAS notes that biting midges are sometimes incorrectly called sand flies; true sand flies are a different group of insects. In Australia, though, people do call biting midges "sandflies," and we cover that version in our guide to sandfly repellent in Australia.
As a calm aside: UF/IFAS describes the bites as irritating and painful, and for some people they can leave long-lasting sore spots. In the US, biting midges are mainly a nuisance, and the main medical concern is allergic reaction to the bites.
When and where no-see-ums bite
Timing is the single most useful thing to know. UF/IFAS Extension reports that no-see-ums bite people outdoors in the early morning and evening, and even during the day on cloudy days when the wind is calm. Females do the biting (only females need blood), and they feed mainly around dawn and dusk, though some species prefer daytime.
Where they live matters just as much. Their larvae develop in and around salt marsh and mangrove swamps, along the shores of streams and ponds, and in muddy ground. In UF's words, "Coastal areas provide primary habitat for biting midges." Females can fly a mean of 2 kilometers, and they do not set up house inside homes.
Put those together and you get the classic no-see-um moment: a still evening on a beach, a dock or a marsh-side deck. That is why they are such a familiar part of winter trips to the Gulf Coast, the Caribbean, Florida and Costa Rica. The good news: once you know the window, you can plan around it instead of heading inside.
Does regular bug spray work on no-see-ums?
Yes. UF/IFAS Extension notes that repellents containing DEET that are typically used as mosquito repellents are also labeled for use against no-see-ums. University of Arizona Extension puts it plainly: "Repellents effective against mosquitos are effective against biting midges."
The CDC lists these active ingredients for EPA-registered insect repellents, framed for preventing mosquito bites:
- DEET
- Picaridin (KBR 3023, called icaridin outside the US)
- IR3535
- Oil of lemon eucalyptus (OLE), plant-derived
- Para-menthane-diol (PMD)
- 2-undecanone, plant-derived
The CDC list is about mosquitoes, not no-see-ums specifically, but it is the right starting point for choosing a spray. If you are weighing the two most common options, our picaridin vs DEET comparison walks through how they differ. Whatever you pick, follow the label for how much to use and when to reapply.
What the research shows against biting midges
Most "best no-see-um repellent" lists rely on anecdotes. There is actually a small body of published field research on repellents against biting midges, and it is worth knowing. Each study below tested one specific product against one group of midges. None of them tested our spray, and results can vary by species and setting.
| Study | Where and which midge | What was tested | What they found |
|---|---|---|---|
| Trigg, J Am Mosq Control Assoc, 1996 | Scotland, Culicoides impunctatus | A PMD (eucalyptus-based) repellent vs DEET, 0.5 ml on the forearm | Both gave 98% protection 8 hours after applying. In a second trial at 8 to 10 hours: 99.5% for PMD vs 97% for DEET, compared with untreated controls |
| J Am Mosq Control Assoc, 2006 | California Central Valley, Leptoconops midges | Lemon eucalyptus spray and lotion, 10 subjects, 6 hours of continuous exposure, DEET as a positive control | Half of the lemon eucalyptus subjects received no bites |
| J Am Mosq Control Assoc, 1991 | Honduras, mostly Culicoides furens (96.3% of midges caught) | 75% DEET liquid, 33% DEET lotion, the original Avon Skin-So-Soft bath oil | 97.9% protection (DEET liquid), 95.9% (DEET lotion), 71.4% (Skin-So-Soft), vs untreated controls. Both DEET formulas did significantly better |
What this tells you: actives from the CDC list, including PMD and lemon eucalyptus, have published field data against biting midges. It does not tell you any single product will perform the same way on your beach, so good application still does a lot of the work.
Does Avon Skin So Soft work on no-see-ums?
This is one of the most common no-see-um questions, and the answer from the one field study we have is: partly. In the 1991 Honduras test, the original Skin-So-Soft bath oil gave 71.4% protection against biting midges compared with untreated skin. Both DEET formulas in the same test did significantly better, at 97.9% and 95.9%.
That study is about the original bath oil tested in 1991, so it says nothing about other products sold under the Avon name today. If you want the most coverage for a long evening outside, a repellent built on a CDC-listed active is the better bet.
How to apply repellent so no-see-ums cannot find a gap
No-see-ums are tiny, which means any patch of skin you miss is fair game. The spray matters, but coverage matters just as much.
- Go low first. Ankles, feet and the tops of your toes are the easiest spots to forget, especially in sandals.
- Then go high. Cover your neck, the back of your ears and along your hairline.
- Apply before the light changes. Put it on before dusk, not after the first bite, since dawn and dusk are the main feeding windows.
- Follow the label. Use the amount it directs, and reapply on the schedule it gives, including after time in the water if the label calls for it.
- Check the gaps between clothes and skin. Wrists and the strip between shorts and socks are common misses.
A spray is great for broad coverage on legs and arms. Wipes are handy for faces, hairlines and travel days. Our wipes vs spray guide breaks down when each one makes sense.
Fans, screens and clothing
Repellent is your first layer. These three habits, drawn from UF/IFAS and University of Arizona Extension guidance, make up a simple no-see-um evening plan so you can stay for the whole sunset.
Turn the fans on high
UF/IFAS notes that no-see-ums are small and weak fliers, so ceiling and window fans on high speed can keep them out of small areas. On a porch or patio, a fan pointed across your seating area is one of the easiest upgrades you can make. Calm air is when they bite, so moving air works in your favor.
Check your screen mesh
Here is the surprise for most people. UF/IFAS reports that most biting midges can pass through 16-mesh insect wire screen and netting, so a smaller mesh is needed. University of Arizona Extension adds that standard 16x16 or 18x16 screens let them through and suggests 30x30 mesh where possible. The tradeoff, per UF, is that finer mesh limits airflow, which is one more reason to pair it with a fan.
Dress for the evening
University of Arizona Extension recommends light-colored long sleeves and hats with fine mesh netting to protect the face and neck. A loose, light layer means less skin for the repellent to defend.
Skip spraying the yard
UF/IFAS explains that spraying for adult midges is not efficient, because new ones keep arriving from their breeding sites. Your time is better spent on personal repellent, fans and screens.
The no-see-um evening plan, in one list:
- Head out with repellent already on, ankles to hairline.
- Pick a seat in moving air, or bring the fan.
- Wear a light long-sleeve layer for the dusk hour.
- Choose a breezy spot over a sheltered corner near the marsh.
- Reapply as the label directs and stay for the sunset.
Our pick for beach and dock evenings
We made Bloc Off Mosquito Repellent Spray for exactly these evenings. Its active is 8% plant-based PMD (para-menthane-3,8-diol) derived from lemon eucalyptus, which is one of the actives on the CDC list. On our product page, the spray is lab-tested for 6+ hours of protection against mosquitoes, ticks and other biting insects. To be clear, we have not tested it on no-see-ums specifically, so the studies above are about PMD and lemon eucalyptus products in general, not our formula.
My co-founder and formulator Cassidy Huang and I spent two years with a Taiwan-based chemist developing it. The formula is DEET-free, alcohol-free and water-based, with aloe vera and chamomile, so it is comfortable to apply generously to ankles and feet, which is exactly what no-see-ums demand. There is also shiso (perilla) in the blend, which keeps it gentle on skin and gives it a clean herbal scent. The protection comes from the PMD. Each bottle is 4 oz (118 ml) and costs $15.00.
For travel days, Bloc Off Wipes come as 10 individually wrapped wipes for $13.00. They are easy to tuck in a beach bag and handy for faces and hairlines where a spray is awkward in the breeze.
FAQ
What keeps no-see-ums from biting you?
A repellent with an active the CDC lists, such as DEET, picaridin, PMD or oil of lemon eucalyptus, applied to all exposed skin and used as the label directs. UF/IFAS also notes that fans on high speed can keep these weak fliers out of small areas, and finer screen mesh helps at home.
Does bug spray work on no-see-ums?
Yes. UF/IFAS Extension says DEET repellents typically used for mosquitoes are also labeled for no-see-ums, and University of Arizona Extension says repellents effective against mosquitoes are effective against biting midges. Check your label and follow its directions.
Does Avon Skin So Soft work on no-see-ums?
In a 1991 field test in Honduras, the original Skin-So-Soft bath oil gave 71.4% protection against biting midges. Two DEET formulas in the same test gave 97.9% and 95.9%, which was significantly better.
Can no-see-ums get through window screens?
Often, yes. UF/IFAS reports that most biting midges can pass through 16-mesh screen. University of Arizona Extension suggests 30x30 mesh where possible. Finer mesh limits airflow, so pair it with a fan.
Are no-see-ums the same as sand flies?
Not in the US. UF/IFAS says biting midges are sometimes incorrectly called sand flies, and true sand flies are a different group. In Australia, biting midges are commonly called sandflies, which we cover in our Australian sandfly guide.
Written by Tanya Lee, Co-Founder of The Superbloc. Sources: CDC, Preventing Mosquito Bites (cdc.gov/mosquitoes/prevention); UF/IFAS Extension EENY 349, Biting midges, no-see-ums Culicoides spp. (C. Roxanne Connelly, revised 2013); University of Arizona Extension, Something's Biting Me but I Can't See It; Trigg, J Am Mosq Control Assoc 1996 (PMID 8827615); J Am Mosq Control Assoc 2006 (PMID 17067050); J Am Mosq Control Assoc 1991 (PMID 2045813). Always read and follow the product label.