Horsefly Bites: Pictures, Treatment, Complications, and More

Medically Reviewed By Avi Varma, MD, MPH, AAHIVS, FAAFP
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Horseflies are a type of large flying insect that lives in the United States and other countries worldwide. They can cause particularly painful bites. In some cases, horsefly bites can lead to complications, such as allergic reactions or infection. Horseflies bite humans in order to feed on blood, also known as taking a blood meal.

This can cause pain and swelling at the site of the bite wound. In fact, due to the way horseflies bite, their bites may be particularly painful and take longer to heal, according to the Illinois Department of Public Health (IDPH).

As a result, identifying horsefly bites and caring for them properly is important.

This article will discuss the symptoms of a horsefly bite, how to identify bites, and when to see a doctor. It will also explain the complications, treatment, and outlook for horsefly bites, as well as discuss ways to prevent bites.

What is a horsefly bite like?

A person stands in a field and strokes the head of a horse.
Steven Ritzer/EyeEm/Getty Images

Bites from a horsefly can be very painful. This is because horseflies cut into the skin with their jaws, rather than just piercing it, as the National Health Service (NHS) Scotland notes. Not only can this cause pain, but the bites can also take a longer time to heal, which may increase the risk of infection.

Horsefly bites can also cause symptoms such as:

  • a raised wheal that is red, flushed, or discolored
  • a visible cut or puncture in the wheal
  • papules, or raised lumps of skin less than 1 centimeter (cm)
  • a large rash or hives
  • dizziness
  • weakness
  • wheezing
  • swelling or puffiness in part of the body, including around the eyes or lips
  • lesions that take a while to heal or show signs of infection, such as:
    • pus
    • increasing pain
    • redness or discoloration
    • swelling

What does a horsefly bite look like?

In addition to other symptoms, certain characteristics of horsefly bites may help you better determine whether a horsefly bit you.

How to identify a bite

If you observe a horsefly biting you, you may notice the mechanism it uses to puncture the skin. Horseflies have serrated mandibles, or jawbones, that cut the skin rather than piercing it and suck up the remaining blood.

You may also be able to identify a horsefly by its size, appearance, and behavior. Yet with more than 350 different species of horseflies and related deerflies in North America, their appearance may vary.

According to the IDPH, some characteristics of horseflies include:

  • a black, light brown, or colorful body
  • two wings
  • solid or patterned eyes, such as rainbow-colored or striped
  • large eyes that may be shiny and green
  • a large body
  • frequent presence around animals and livestock, as well as bodies of water

View more about bug bite pictures and learn more about identifying different bites.

Horsefly bite pictures

Below are some examples of what a horsefly bite might look like, as well as some pictures of horseflies to help you identify them.

A horsefly bite can cause a raised red or flushed wheal on the skin where the horsefly has torn the skin.

A horsefly bite can cause a raised red or flushed wheal on the skin where the horsefly has torn the skin.

Liz Tracy Photography/Shutterstock

Horsefly bites can cause swelling and raised skin around the bite wound.

Horsefly bites can cause swelling and raised skin around the bite wound.


Horseflies can be light brown in color and have large, patterned eyes. They use serrated mandibles to cut the skin.

Horseflies range in color from black to brown, with black or colored and patterned eyes.

Horseflies range in color from black to brown, with black or colored and patterned eyes.


Are there any potential complications of a horsefly bite?

Horsefly bites are susceptible to infection because they can take a long time to heal, according to the NHS.

Other complications of a horsefly bite include:

  • mild to severe allergic reactions and anaphylaxis
  • myiasis infestation of larvae
  • cellulitis due to infection

Sometimes horseflies can transmit a disease called tularemia. Other insects and animals also carry tularemia.

Symptoms of tularemia from an insect bite may include:

  • a skin ulcer at the site of the bite
  • swollen lymph glands, typically in the armpit or groin
  • fever

While tularemia can be life threatening, the Centers for Disease Control and Prevention (CDC) note that most cases are treatable with antibiotics.

When should I see a doctor for a bite?

Seek advice from a doctor if you have a bite that is not improving with at-home care or is causing worsening symptoms.

It is also important to seek medical advice as soon as you notice signs of infection in a bite.

Call 911 for symptoms of severe allergic reaction or infection

Sometimes, horsefly bites can cause severe allergic reactions, anaphylaxis, or cellulitis, according to 2022 research. These conditions are emergency medical situations.

Seek emergency medical care or call 911 for the following symptoms after a bite:

  • lightheadedness or faintness, or collapsing or weakness
  • difficulty breathing, such as fast or shallow breathing, or wheezing
  • rapid heartbeat
  • confusion or anxiety
  • loss or changes in consciousness
  • raised rash or hives that may be itchy
  • nausea, vomiting, or stomach pain
  • fever
  • swelling
  • skin that feels painful, hot, and swollen
  • red, purple, or discolored streaks that spread from the bite site
  • swollen lymph nodes that are sensitive to pressure

How do you treat a horsefly bite?

Treatment for a horsefly bite may depend on your symptoms and whether you experience any complications.

Most bites that do not have complications are manageable with self-care and wound cleaning, per 2022 research.

These self-care methods can include:

  • keeping the bite clean by washing the bite wound with soap and water
  • applying a cold compress to the bite for at least 10 minutes
  • elevating the affected body part, if possible
  • avoiding any other remedies, such as vinegar and baking soda
  • avoiding scratching the bite or breaking the skin further
  • keeping your fingernails short and clean

It is important to avoid scratching, catching, or making any other unnecessary contact with the bite to reduce the risk of infection. If children have a bite, it may help to keep their fingernails short or use mittens to prevent scratching.

It can also help to ask a pharmacist about over-the-counter care options. These can include mild pain relief medications, antihistamines, or anti-itch creams.

If your bite is not improving with at-home care, contact your doctor for advice. If you experience complications, such as infection, they may prescribe additional treatment.

What is the outlook for a horsefly bite?

Most bites will improve within a matter of days and can be treatable at home, the NHS says.

Recovery and healing may take longer if you experience complications from a horsefly bite. The exact time frame and recovery process will depend on what symptoms and conditions you experience with a complicated bite.

For a more individual outlook on what you can expect from your condition, contact your doctor.

How do you prevent horsefly bites?

You can take many steps to avoid horsefly bites and other insects. These prevention methods can include:

  • covering exposed skin with clothing
  • wearing light-colored clothing
  • applying insect repellent that contains at least 50% diethyltoluamide (DEET)
  • avoiding the use of strongly scented products, such as perfume or deodorant
  • limiting time spent by bodies of water, such as ponds or swamps
  • keeping food and drink covered while eating outside
  • fixing window and door screens
  • cleaning up or avoiding piles of discarded items or waste, such as vegetation, that may attract flies


Horsefly bites can be painful and cause other uncomfortable symptoms of swelling, such as wheals or rash. This is because horseflies bite using serrated mandibles that cut the skin. This can also add to your healing time and present a risk of infection.

Self-care and wound cleaning can help horsefly bites heal without further medical care. But complications can occur from horsefly bites. Seek immediate advice from a doctor for symptoms of infection and emergency medical care for symptoms of severe allergic reaction or cellulitis.

You may be able to prevent bites by covering the skin and avoiding things and places that attract flies.

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Medical Reviewer: Avi Varma, MD, MPH, AAHIVS, FAAFP
Last Review Date: 2022 Sep 29
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