Deer flies are notoriously difficult to repel. Unlike mosquitoes, which can be kept at bay with a good spray-on repellent, deer flies don’t respond well to chemical repellents, including DEET. That means keeping them away requires a combination of physical barriers, visual tricks, and smart timing rather than relying on a single product.
Why Standard Repellents Don’t Work
If your first instinct is to reach for bug spray, you’re not alone, but it won’t help much here. The University of New Hampshire Extension notes plainly that no repellents really work on deer flies, horse flies, or greenheads. DEET, picaridin, and other active ingredients that reliably deter mosquitoes and ticks have minimal effect on these biting flies.
The reason comes down to how deer flies find you. Mosquitoes locate hosts primarily through carbon dioxide and body odor, which repellents can mask. Deer flies rely heavily on vision. They’re attracted to movement, shiny surfaces, warmth, and carbon dioxide. A chemical coating on your skin does little to counter the visual and thermal cues that draw them in. This is also why deer flies can be relentless around swimming pools: the shiny water surface and movement of swimmers pull them in from a distance.
Physical Barriers That Actually Help
Because you can’t repel deer flies chemically, blocking them physically is your most reliable option. Long sleeves, long pants, and a hat with a head net dramatically reduce the number of bites you’ll get. Deer flies tend to target the head, neck, and shoulders, so head protection matters more than you might expect. Mesh head nets designed for beekeeping or outdoor work are inexpensive and highly effective.
Clothing color matters too. Deer flies are drawn to dark colors and high-contrast movement. Wearing light-colored clothing, particularly light blue, white, or tan, makes you less visible to them. Avoid dark shirts and hats when you’re in deer fly territory during peak season.
The Sticky Hat Trick
One of the most effective and surprisingly simple deer fly strategies is a sticky trap worn on your hat. You attach adhesive patches (the same kind used in commercial fly traps) to the back of a light-colored baseball cap. As you walk, deer flies circle your head and land on the hat, where they get stuck.
This works because of a consistent behavior pattern: deer flies approach from behind and circle the head before biting. A sticky patch on the back of a cap intercepts them at exactly the right moment. Some outdoor workers and hikers report catching dozens of flies on a single walk. You can buy purpose-made adhesive strips for this, or use any outdoor fly tape cut to size. It looks a little odd, but it works far better than any spray.
Reducing Deer Flies Around Your Yard
Deer flies breed in moist soil and decaying vegetation near water. If your property borders a pond, stream, marsh, or consistently wet area, that’s likely where they’re coming from. You can’t eliminate them entirely from a landscape, but reducing standing water, draining boggy patches, and keeping vegetation trimmed around wet areas can lower their numbers over time.
Hanging visual traps in your yard can also help. Commercial deer fly traps use a dark, moving target (often a black ball or dark-colored panel) coated with adhesive. The dark object mimics the silhouette of a large animal, drawing flies in. These traps work best when placed in sunny areas between the breeding habitat and the spaces where you spend time, like a patio or garden path. They won’t eliminate every fly, but they can meaningfully reduce the population in a small area.
Timing and Location Strategies
Deer flies are daytime biters, most active on warm, sunny, calm days from late spring through midsummer. They’re far less active on overcast days, in windy conditions, and during early morning or evening hours. If you have flexibility in when you do outdoor activities, shifting to early morning, late evening, or breezy days can make a noticeable difference.
They also tend to patrol edges: the boundary between a wooded area and a clearing, the perimeter of a pond, or the tree line along a trail. If you’re hiking or working outside, staying in open, breezy areas rather than lingering at wooded edges reduces your exposure. Moving steadily also helps. Deer flies are persistent followers but tend to give up if you keep a brisk pace through their territory rather than stopping in one spot.
What Happens When You Do Get Bitten
Deer fly bites hurt. Unlike mosquitoes, which pierce the skin with a thin needle-like mouthpart, deer flies slash the skin and feed on the pooling blood. The result is a sharper initial pain, more bleeding, and often a larger, more swollen welt.
If you’re bitten, wash the area with soap and water right away. Apply an ice pack wrapped in cloth for at least 20 minutes to bring down swelling. Keep the area elevated if possible. An over-the-counter antihistamine can help with itching, and a standard anti-inflammatory painkiller can handle soreness. The most important thing is to avoid scratching, which increases the risk of infection.
Most deer fly bites heal on their own within a few days. Watch for signs of a skin infection: increasing redness or red streaks spreading from the bite, unusual warmth, swelling that gets worse instead of better, pus or drainage, fever, or swollen lymph nodes near the bite. These symptoms indicate a bacterial infection that needs medical treatment.
Disease Risk From Deer Fly Bites
Deer flies can transmit a bacterial infection called tularemia, sometimes known as “deer fly fever” or “rabbit fever.” It’s caused by the bacterium Francisella tularensis and can cause fever, skin ulcers, and swollen lymph nodes. The good news is that tularemia is rare. Fewer than 200 cases were reported across the entire United States in 2023. The risk from any single bite is very low, but it’s worth knowing the possibility exists, especially if you develop an unexplained fever or a slow-healing sore at a bite site within a couple of weeks of being bitten.