What to Know About Black Flies (Buffalo Gnats)

Medically Reviewed by Stephanie S. Gardner, MD on February 21, 2024
3 min read

Black flies (buffalo gnats) are small dark flies that come out during early summer and late spring. These flies belong to the Simuliidae family and are called buffalo gnats because they have a humpback appearance. 

They suck blood as a necessary part of their reproduction process. The female black fly has to suck blood from an animal and human prey to complete the reproduction cycle. 

Typically, black flies bite domestic animals and mammals, including humans. Buffalo gnat bites can cause itchiness and pain for many days.

Black flies bite humans and animals, causing nuisance, pain, discomfort, or even livestock death. They often bite people around their necks and heads. 

If a massive swarm of black flies attacks birds, they can kill them too. They can also enter the livestock's ears and noses, clogging their respiratory tracts. Incidents of this happening in chickens have been reported, and the animals died of suffocation. 

When black flies bite, they also release saliva, which causes toxic shock syndrome, killing the animal. Some black fly species also carry serious diseases, such as leucocytozoonosis, a condition found in chickens, ducks, geese, and turkeys. 

There are six species of black flies in North America that feed on humans. Some other species may be attracted to humans, too. Although they do not bite, they can enter the eyes, nose, mouth, and ears, causing a nuisance to people playing or working outside. 

Black fly bites on humans look similar to a mosquito bite. They cause swollen bumps on the skin that are small and red in appearance. These bumps are also very painful and itchy, becoming fluid-filled blisters in some cases. 

Black fly bites on humans can have different reactions, such as a tiny puncture wound or a huge swelling on the skin. They can also cause: 

If you are experiencing only minor black fly bite symptoms, here are some ways to treat them: 

Soap and water. Wash the area with mild soap and water. This cleans the area and lowers the irritation. Do not use a towel roughly on the area after washing it so you avoid making your symptoms worse. 

Cold compress. A cold compress reduces swelling and irritation following a black fly bite. Put the cold compress on your skin for 10 minutes a few times a day. Do not put ice directly on your skin. Instead, make a cold compress out of ice in a plastic bag or a cloth soaked in icy water. 

Antihistamines. If you have irritation and itchiness at the site of the bite, you can use antihistamines to treat the allergic reactions. These medications are available over-the-counter (OTC). Follow the instructions correctly when using OTC medications. 

Anti-itch creams. You can also apply an anti-itch cream to the area to relieve itchiness and redness. These creams may contain corticosteroids. This black fly treatment is helpful if you've had symptoms for a couple of days and they are causing you discomfort. 

Sometimes, black fly bites need medical attention. You should consult a doctor if: 

  • A black fly bit you near your eyes or mouth. 
  • Symptoms have not gone away even after 14 days. 
  • You have serious symptoms, like pus, on your skin. 

The doctor may prescribe a cream to treat the infection. 

It is not always possible to control the reproduction and spread of the black fly population. Instead, you can try to avoid a black fly bite. Here are a few ways: 

  • Avoid infested areas, especially in the dusk and early morning during summer and spring, since black flies are most active at these times. 
  • Gnats are weak fliers, so using fans can keep them away. 
  • Cover your skin properly. Wear long-sleeved shirts and long pants. 
  • Wear shirts with zippers rather than buttons since buttoned shirts have spaces that allow black flies to enter. 
  • Wear light-colored clothes, since black flies are attracted to dark colors. 
  • Wear a head net when going to an area with a large population of black flies.