5 Types of Fly Bites You Might Get —And How To Treat Them

Here's everything you need to know about itchy, sometimes-painful fly bites.

Wild garden small flying insect

Flies dive-bomb your face, march across your food, and can bite. Annoying? Sure. Painful? Sometimes.

Flies are carriers and transmitters of numerous diseases due to breeding and feeding on animal waste, garbage, and human foods. They can carry bacteria and viruses that cause symptoms such as diarrhea and eye infections, among others.

But are fly bites dangerous? Rarely. However, their bites can hurt, and some people have more serious allergic reactions to their saliva.

Here are five common U.S. flies and what their bites can–and can't–do to you.

Horse Fly Bites

Horse flies received their common name because they are notorious pests of horses and other mammals.

While horse flies are not known to be vectors of disease, they give painful bites that can cause allergic reactions.

Horse flies are persistent and will continue to bite their host until they either succeed in procuring their blood meal or are killed. Female horseflies are even known to chase their intended targets for short periods. It's best to wear light-colored clothing and insect repellant to help prevent bites from these unwanted visitors.

Sand Fly Bites

Sand flies are tiny (about 1/4 the size of a mosquito), hairy insects with large black eyes, and are distinguished by their hairy wings.

Sand fly bites can cause small red bumps and blisters that may itch and swell. Antiseptic and soothing lotions will help ease itching and prevent infections from developing.

According to the Centers for Disease Control and Prevention (CDC), in some cases, sand flies can transmit a parasitic disease called leishmaniasis. There are several different forms of leishmaniasis in people. The most common forms are cutaneous leishmaniasis, which causes skin sores that can change in size and appearance over time. They may start as bumps or lumps and end up as ulcers. The sores can be painful.

Almost all cases of leishmaniasis diagnosed in the U.S. have been in people who became infected while traveling or living in other countries, though occasional cases of cutaneous leishmaniasis have been acquired in Texas and Oklahoma.

U.S. troops in the Middle East often have trouble dealing with sand flies, said James Diaz, MD, professor and director of the environmental and occupational health sciences program at Louisiana State University School of Public Health.

Deer Fly Bites

Larger than a house fly but smaller than a horse fly, deer flies are aggressive, and their bites (described as skin slashing) can be pretty painful. The deer fly has a mouth with razor-sharp "lips," which it uses to slice the skin open, so it can feed on the blood. In addition, some people experience an allergic reaction to the salivary secretions released by the insects as they feed.

According to the United States Department of Agriculture (USDA), deer flies are the "premier daylight bloodsucker during the summer." You can expect them from June into August and they prefer sunny places, pretty much disappearing in the shaded forest.

Antihistamines, along with antiseptic and soothing lotions, are usually enough to tame their bites. But deer flies occasionally transmit tularemia, or "rabbit fever," a bacterial infection usually treated with antibiotics.

Common in the U.S., deer flies are found near sunny lake edges, trails, and fields. They only feed during the day, biting any exposed skin but prefer the head, so cover your skin and wear a hat.

Black Fly Bites

Black flies are small, hump-backed, and dark-colored. They slash the skin to feed on blood. They will bite any exposed skin and are especially good at getting under clothes. You might not notice a bite until you have a small scab, but some people will get a large, itchy welt that will last for days.

These flies are sometimes called buffalo gnats and are very common in the United States. Although they bite, they don't transmit diseases, at least not in America.

Reactions to the bites can be a small puncture wound or a swelling as big as a golf ball. Some people react to a fly bite with a collection of symptoms known as "black fly fever," which can involve headache, nausea, fever, and swollen lymph nodes.

Black flies are only around during the day and they appear in the late spring (April) to early summer (July), especially along creeks and rivers.

Biting Midges or Gnat Bites

Biting midges are small, gray, two-winged insects, less than 1/8" long. Often, you'll feel the bite (they hurt) without ever seeing the culprit—hence their "no-see-ums" nickname.

Midge or gnat bites look a lot like mosquito bites: small, red, itchy lumps and sometimes a red welt or blister. It's the female who bites, taking blood using an elongated jaw with small cutting teeth. Biting midges tend to deliver their trademark burning sting at dusk and dawn, though biting may continue throughout the night.

Biting midges are a known transmitter of Mansonella ozzardi, a human nematode parasite. Although the majority of people don't have symptoms, some people have experienced fever, body aches, headaches, edema, and other symptoms.

These pesky insects are a nuisance, particularly in hot and humid areas. Biting midges are found throughout the United States but favor coastal areas, near farms, or in wet mud, mangrove swamps, and salt marshes.

Stable Fly Bites

Stable flies look similar to house flies but have a painful bite, thus the common name "biting house fly". They are global pests of livestock (cattle and horses), domestic pets, and people.

Stable flies typically bite in the early morning or late afternoon; they are most abundant in late summer and fall. They often attack the ankles, inflicting a sharp, stabbing pain. Unlike many other blood-feeding insect bites on humans, the bite site does not appear to get irritated, and bites rarely result in allergic reactions.

Stable flies are known for attacking people in certain regions of the U.S.—coastal New Jersey, Lake Superior and Lake Michigan shorelines, Tennessee Valley, and along the Florida panhandle to Louisiana.

Fly Bite Treatment

Fly bites, like most bug bites, can be safely treated at home with topical medication, such as hydrocortisone cream or ointment, or an oral antihistamine to reduce the itch.

However, sometimes a bug bite or sting could turn into something serious—especially if you are allergic to the saliva or venom or if the bug is carrying a disease. Talk with your healthcare provider if you experience fever, swelling, or increasing pain following an insect bite.

You should go to the emergency room immediately if you experience any of the following symptoms after a bug bite or sting:

  • Difficulty breathing
  • A sensation that your throat is closing
  • Swollen lips, tongue, or face
  • Chest pain
  • A racing heartbeat that lasts more than a few minutes
  • Dizziness
  • Vomiting
  • Headache

A Quick Review

Fly bites, no matter which type of fly, are annoying but usually resolve with time, topical medication, or antihistamines. For some people a stronger reaction or allergic reaction can occur, which may require a visit to your healthcare provider or in rare cases, a trip to the emergency room.

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  3. European Centre for Disease Prevention and Control. Plebotomine sand flies - Factsheet for experts.

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  5. U.S. Department of Agriculture. Biting bugs and plants to avoid.

  6. MITMedical. Oh, deer [fly].

  7. Centers for Disease Control and Prevention. Tularemia.

  8. Purdue University Entomology Department. Black flies: Biology and public health risk.

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  11. Department of Entomology and Nematology, University of Florida. Featured creatures.

  12. American Academy of Dermatology Association. Bug bites and stings: When to see a dermatologist.

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