What to Do If You Get a Horsefly Bite
In general, sand fly bites are painful and may cause red bumps and blisters. These bumps and blisters can become infected or cause skin inflammation, or dermatitis.
Types of Fly Bites, Symptoms, and Treatment
Flies are an annoying yet inevitable part of life. One pesky fly buzzing around your head can throw off an otherwise lovely summer day. Most people have been bitten by a fly at least once in their lifetime. In most cases, it’s nothing more than irritating.
According to the University of California Museum of Paleontology, there are about 120,000 species of fly throughout the world, and many of them bite animals and people for their blood. Some species carry diseases, which they can transmit to humans thorough bites.
Sand flies are about 1/8 of an inch long, and have hairy, brownish-gray wings. They hold their wings above their bodies in a “V” shape and are most active between dusk and dawn. The larvae look like worms.
They’re found mainly in tropical and subtropical climates. They breed in places with a lot of moisture, such as decaying plants, moss, and mud. In the United States they’re mostly found in the southern states.
Sand flies eat nectar and sap, but females also feed on the blood of animals and humans.
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Symptoms
In general, sand fly bites are painful and may cause red bumps and blisters. These bumps and blisters can become infected or cause skin inflammation, or dermatitis.
Sand flies transmit diseases to animals and humans, including a parasitic disease called leishmaniasis. According to the Centers for Disease Control and Prevention (CDC) , leishmaniasis is rare in the United States. You may contract it during travel to a foreign country. There are no vaccinations to prevent leishmaniasis. Symptoms include skin sores weeks or months after the bite. They often clear up without treatment, but can be serious in some cases.
Treatment
You can apply hydrocortisone or calamine lotion directly to the bites to help them heal and reduce itching. Oatmeal baths and aloe vera can also soothe itching. For persistent sores or ulcers, you should see a doctor.
The bloodsucking tsetse fly is about 6 to 15 millimeters long and its mouth points forward. It makes its home in the tropics of Africa, and prefers shady places in wooded areas. It hides in tree trunk holes and between tree roots.
Symptoms
The tsetse fly bite is often painful and can cause red bumps or small red ulcers at the site of the bite. It can also transmit sleeping sickness (trypanosomiasis) to animals and humans.
Trypanosomiasis is generally not found in the United States except in people who have traveled to Africa. Early symptoms include headache, fever, and muscle aches. Later, you may experience mental confusion or coma. Trypanosomiasis causes swelling in the brain and is fatal, if untreated.
Treatment
If you’ve been bitten by a tsetse fly, your doctor can run simple blood tests for sleeping sickness.
Antitrypanosomal medications, such as pentamidine, are highly effective in treating sleeping sickness.
Deer flies are about 1/4 to 1/2 of an inch long, with brownish-black bands on their otherwise transparent wings. They may have gold or green eyes on their small, rounded heads.
They are most active during spring and like to be near lakes, swamps, or other bodies of water. The larvae resemble maggots.
Symptoms
Deer fly bites are painful, and will cause red bumps or welts. They transmit a rare bacterial disease known as rabbit fever (tularemia). Symptoms include skin ulcers, fever, and headache. Tularemia can be successfully treated with antibiotics, but without treatment, it can be fatal.
Treatment
To treat deer fly bites, clean the affected area with soap and water. You can apply ice to the area to treat pain. You can also take allergy medicine like diphenhydramine (Benadryl) to reduce itching, which can prevent secondary infection.
Black flies are small, ranging from 5 to 15 millimeters as adults. They have an arched thoracic region, short antennae, and wings that are large and fan-shaped. They are often found near bodies of water where their larvae grow.
Black flies can be found throughout most of the United States, but their bites do not appear to transmit diseases here. In other regions of the world, including Africa and South America, their bites can transmit a disease called “river blindness.”
Symptoms
Black flies typically bite near the head or face. Their bites leave a small puncture wound, and can result in anything from slight swelling to a swollen bump the size of a golf ball. Other symptoms can include headache, nausea, fever, and swollen lymph nodes. When these symptoms occur, they’re referred to as “black fly fever.”
Treatment
Apply ice to the area for fifteen minute intervals to reduce swelling from a black fly bite. You can apply cortisone or prescription topical steroids to the affected area. Washing the area with soap and water can reduce the risk of infection.
Biting midges are extremely small at only 1 to 3 millimeters in length. The adults can be reddish after they’ve eaten, or gray when they haven’t. The larvae, which are white, can only be seen with a microscope.
Symptoms
Bites from biting midges resemble small red welts. They can be found all over North America. The bites are persistently itchy, and many people with bites feel like something is biting them but they can’t see what.
In other parts of the world, biting midges can transmit filarial worms to humans, which live inside the skin. This can result in dermatitis and skin lesions.
Treatment
Avoid scratching the bites of biting midges. Treatment with cortisone or prescription topical steroids can help. For natural remedies, you can apply aloe vera topically.
Stable flies strongly resemble the standard house fly, but are slightly smaller in size at 5 to 7 millimeters. They have seven circular black spots in a checkerboard pattern on their abdomen.
Stable flies can be found all over the world, and are particularly prevalent around livestock. In the United States in areas like New Jersey, Lake Michigan shorelines, the Tennessee Valley, and the Florida panhandle, the flies are most likely to bite humans.
Symptoms
Stable fly bites often feel like sharp needle pricks, and occur most often on the feet, ankles, behind the knees, and legs. Red rashes and small, raised red bumps are common at the bite mark.
Treatment
You can take medications like Benadryl to reduce itching and swelling and apply ice to the bite mark to reduce pain. Benadryl can also reduce hives caused from the bite.
Preventing fly bites is much easier and less painful than having to treat them. You can’t avoid flies entirely, but you can make your yard less inviting by keeping grass and plants well-trimmed.
Talk to your doctor if you plan on visiting a foreign country. You may need vaccines or medication prior to your trip. Also see your doctor if you experience fever, swelling, or increasing pain following an insect bite.
Last medically reviewed on March 17, 2017
How we reviewed this article:
Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
- Biting Flies. (n.d.)
idph.state.il.us/envhealth/pcbitingflies.htm - Diptera. (n.d.)
ucmp.berkeley.edu/arthropoda/uniramia/diptera.html - Leishmaniasis FAQs. (2013, January 10). Retrieved from
cdc.gov/parasites/leishmaniasis/gen_info/faqs.html - Mann, R.S., Kaufmann, P.E., & Butler, J.F. (2013, January). Featured Creatures. Sand Fly
entnemdept.ufl.edu/creatures/misc/flies/Lutzomyia_shannoni.htm - Sleeping sickness. (2014, December 7). Retrieved from
nlm.nih.gov/medlineplus/ency/article/001362.htm - Symptoms of insect bites and stings. (2017, January 7)
nhs.uk/Conditions/Bites-insect/Pages/Symptoms.aspx - Tsetse flies. (n.d.)
who.int/water_sanitation_health/resources/vector178to192.pdf - Mayo Clinic Staff. (2015, July 8). Tularemia: Symptoms. Retrieved from
mayoclinic.com/health/tularemia/DS00714/DSECTION=symptoms
What to Do If You Get a Horsefly Bite
If you’re bitten by a horsefly, disinfect the wound and apply antiseptic cream. Most bites will heal on their own but watch for signs of infection. If you have difficulty breathing, a rash, or worsening pain, see a doctor immediately.
Chances are you’ve been bitten by a horsefly on more than one occasion.
If you’re not immediately familiar with this pesky insect, it’s a large, dark fly. You can generally recognize it by its size. A horsefly can be as long as 1 inch (2.54 centimeters), making it much larger than the average fly.
Read on to find out what you should do if a horsefly bites you.
If you’ve ever been bitten by a horsefly, you know that it hurts.
The fly’s mandible is what makes these bites so painful. The mandible is essentially the insect’s jaw. It’s shaped like scissors and can cut right into the skin.
The mandible is also equipped with small hooks to help the horsefly lock in to feed better. Once the horsefly is locked in, it eats the blood from the skin.
This bite can cause:
- a sharp, burning sensation
- itchiness
- inflammation
- swelling around the bite area
- a bruise, in some cases
Aside from the momentary pain they cause, horsefly bites are not generally harmful to humans. These bites are usually only a problem for horses.
This is because horseflies carry equine infectious anemia, also known as swamp fever. When they bite an equine animal, they can transmit this life threatening disease.
If infected, a horse may experience a fever, hemorrhaging, and general illness. Some horses do not experience any symptoms, but they may still transmit the disease to other equine animals.
Horseflies are found throughout North America. They are highly concentrated in hot, humid states, such as Florida. In some regions, horseflies are pretty much unavoidable, especially in the summer months.
Horseflies are most active during the daylight hours, particularly in the summer. They attack large mammals, such as humans, dogs, and, of course, horses.
They’re most attracted to moving objects and dark objects. They’re also attracted to carbon dioxide. This may explain why all of those outdoor summer activities that get you sweating and breathing heavy seem to bring out the horseflies.
If you’ve ever thought that a horsefly was out for vengeance, you may be right. Pest World states that female horseflies in particular are very persistent. They’ve been known to chase their victims for a short time if their first bite does not get them the satisfying meal they were hoping for.
Horseflies can be distinguished by their color.
The upper part of a horsefly is white and typically marked by a few vertical black lines. The lower segment of the fly is solid black.
Cleanse the bite and apply over-the-counter antiseptic spray or ointment to help keep the wound clean and decrease irritation and itchiness. In most cases, a horsefly bite can heal on its own in a few days.
Be sure to watch the area for signs of an infection, such as excessive pus or a foul odor. If you have any unusual symptoms, consult a doctor.
Certain insect bites can cause more serious reactions. If you have difficulty breathing, a rash that spreads, or worsening pain, seek medical attention.
If you’ve been bitten by a horsefly, the bite will generally heal in a matter of days. You typically will not experience any adverse side effects.
If your bite has not healed within 1 week, or if you’re experiencing unusual symptoms such as dizziness or worsening pain, consult a doctor. They can assess your bite and determine any next steps.
To prevent future horsefly bites, apply insect repellent before going outdoors. If possible, stick to light-colored clothing. Horseflies are attracted to darker colors, so this may help keep them away.
Last medically reviewed on December 31, 2021
How we reviewed this article:
Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
- Cordes T, et al. (2020). Equine infectious anemia.
aaep.org/horsehealth/equine-infectious-anemia - Horse and deer flies. (n.d.).
mdc.mo.gov/discover-nature/field-guide/horse-deer-flies - Horse flies. (n.d.).
pestworld.org/pest-guide/flies/horse-flies - Insect bites and stings. (2019).
nhs.uk/conditions/insect-bites-and-stings
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