HomeHealth articleshorsefly biteWhat Does a Horsefly Bite Look Like?

Horsefly Bite - Symptoms, Treatment, and Prevention

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A horsefly bite is a small red hive caused by the female horsefly, a blood-sucking insect. Read the article below to know more.

Medically reviewed by

Dr. Nagaraj

Published At November 21, 2022
Reviewed AtNovember 21, 2022


A buzzing fly could be the most annoying thing to anybody unless it bites too. Although most flies do not bite, few flies do, for example, horseflies. Horseflies are insects that look similar to house flies. They are also called green-headed monsters and belong to the Tabanidae family of insects. They are black and brown with stripes on their chests and 0.75 to 1.25 inches long in size. They are large flies and have large compound eyes. The female horsefly is a blood-sucking insect, as it requires specific proteins in the blood to produce eggs. They usually feed on large dark-colored animals like horses but may feed on humans too.

What Does a Horsefly Bite Look Like?

Horseflies have a distinct mouthpart that tears through the flesh in scissor-like action rather than making a puncture hole. They then lock into the skin using small hooks to suck better. The saliva that gets injected causes a sharp burning sensation. The bite is more painful than a mosquito bite, as the horseflies do not inject mild anesthetic like the mosquitos. As a result, the skin turns red, itchy, and swollen. Raised rashes (known as hives or urticaria) may also be experienced, depending on the bite.

When Do Horseflies Bite?

Horseflies are common in damp areas and warm climates. They are common in pasturelands near creeks, long grasses, and woodlands during summer. The peak season for horseflies is between May and September, the time when they mate and reproduce.

Are Horseflies Dangerous?

Horseflies are generally not harmful to humans except for painful bites. Horseflies usually feed on nectar from flowers, but during the mating season, female horseflies feed on blood. Female horseflies require specific proteins in the blood for their reproduction. Horseflies track their host by size, color, and smell. Hence, they prefer dark and big animals and follow the source of carbon dioxide that the animal exhales. The flies mate during the summer when people like to go out too. The more the sources for blood, the more hungry the horsefly gets and the more aggressive they become. Hence the horseflies appear to have an aggressive nature.

However, horseflies could cause problems for horses, as they can carry equine infectious anemia. The condition is a life-threatening disease, and horseflies can transmit this infection. Infected horses may have a fever, hemorrhaging, and weakness; some may have no symptoms but transmit the disease.

What Are the Symptoms of a Horsefly Bite?

Horsefly bite causes pain, redness, and a hive around the site.

The symptoms usually go away. Allergic symptoms include:

  • Intense itching sensation around the bite area.

  • Wheezing.

  • Dizziness.

  • Swelling in the body, including the eyes.

Severe anaphylactic reaction to a horsefly bite symptoms include:

  • Swollen tongue.

  • Swelling of the throat.

  • Swelling of the face, lips, hands, and feet.

  • Breathlessness.

  • Nausea and vomiting.

Immediate medical attention is required if anaphylactic symptoms appear.

What Is the Treatment for a Horsefly Bite?

The treatment for a horsefly bite is like any other insect bite. The main concern would be the occurrence of infection. Since horseflies tear the skin rather than making small puncture holes like other insects, there are chances of infection. If the bite gets infected, consult a doctor immediately.

If a horsefly bites:

  • Avoid scratching the area. Scratching could increase the risk of infection.

  • Clean the bite area properly with soap and warm water.

  • Place a cold compress for ten minutes over the bite to help ease the pain and reduce the swelling.

  • If necessary, take an antihistamine to relieve the itching.

When to Consult a Doctor?

Horsefly bites are usually harmless unless there is a secondary infection or an allergic reaction.

Seek medical help immediately in case of the following symptoms:

  • Spreading redness.

  • Swelling.

  • Excessive pus discharge.

  • Foul smell.

  • Wheezing.

  • Increased heart rate.

  • Nausea and vomiting.

  • Loss of consciousness.

  • Swollen lips, throat, and face.

  • Difficulty in swallowing.

  • Dizziness.

  • Swollen glands.

  • Fever.

How to Get Rid of Horseflies?

It is difficult to get rid of horseflies, especially in summer, as their habitat is widespread. However, certain simple practices can help reduce the chances of a horsefly bite:

  • Avoid going to places where the flies are active, like damp areas during summer.

  • Insect repellents can help prevent horsefly bites, but this might not be as effective as it is for mosquitoes. Repellents with 50% DEET (diethyltoluamide) are the most effective.

  • Wear full-sleeved light-colored clothing and shoes. Horseflies are attracted to large dark-colored objects. Hence, wearing a light-colored outfit could help be unattractive to horseflies.

  • Using bright-colored body paints could help hide from the attention of horseflies due to their preference for dark colors.

  • Horsefly traps are another method to keep horseflies away from cattle. For example, hanging a sticky black ball that moves with the wind could trap horseflies. A malaise trap is a large net that catches flies; by being their flight path.

  • Clean the bushes or woods around the house and drain damp areas to avoid horsefly breeding.

  • Clean the lawns and yards from piles of rubbish, leaves, and other vegetation that could attract flies.

  • Do not walk in tall grass.

  • Avoid using perfumed cosmetics, as the smell may attract flies.

  • Install net screens for windows and doors of the house to prevent the entry of horseflies.

What Is the Outlook of a Horsefly Bite?

The horsefly bite generally heals on its own within a few days. If the horsefly bite does not heal within one week or shows unusual symptoms consult a healthcare professional.


Horseflies, also known as green-headed monsters, are harmless insects except for their painful bites. They have distinct mouthparts that can scissor through the skin and tear the flesh. They are attracted to large dark-colored animals and follow them tracking the carbon dioxide exhaled. Generally, horsefly bites feed on flowers for nectar, but during the mating season, female horseflies feed on warm-blooded animals for blood. This is because female horseflies require specific blood proteins for reproduction.

The mating season for the horseflies is usually in the summer months; it is also the time when people like to go out, thus making the horse flies aggressive toward their prey. Horseflies do not usually transmit pathogens to their host, but their bites are painful and itchy and may result in a secondary infection from scratching. Horsefly bites are prevented by wearing full-sleeved light-colored clothing and not going to breeding sites. Although horsefly bites are not dangerous, in case of any allergic or anaphylactic reaction, seek medical help immediately. Usually, the horsefly bites heal on their own within a few days without any treatment.

Dr. Nagaraj
Dr. Nagaraj



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