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black fly bites on a dog stomach

don't panic! they look way worse than they actually are

 The essentials

  • Black or horse fly bites are mostly harmless — The stings from these pesky insects aren’t as bad as they look. But even mild symptoms like itching can make your dog uncomfortable. If bites look worse after a few days or won’t stop scratching, talk to your vet.
  • 🚨 It’s rare, but allergic reactions can be serious — Hives or swelling in areas other than the bite is a major sign of anaphylaxis. If you notice this, call your vet immediately.
  • Seasons don’t matter — Bug bites and stings can happen at any time of the year, so year-round prevention is important.
  • Don’t use human bug sprays — Protect your pup from annoying fly, flea, tick, and mosquito bites with a dog bug spray.

Black flies — also referred to as gnats or buffalo gnats – are known to swarm in large groups. That sounds bad, but unlike diseases that may come along with tick and mosquito bites, black fly bites are mostly harmless and heal without medical attention — even though they look scary.

How to identify a black fly bite

🔍 What to look for: A flat, red splotch that may or may not be outlined. It’s often called a ‘bullseye’ due to the outline, but the entire splotch may sometimes be a completely dark red lump. Black flies tend to bite exposed areas of your pup’s skin like their belly or ears.

Different types of fly bites

Small flies, like yellow flies and no-see-ums, leave a smaller mark. Larger flies, like black and horse flies, primarily buzz around large farm animals and can sometimes draw blood.

Adults are small (1/16 inch), have a stout, dark-colored, rounded back, broad wings, and short legs. They have few hairs on their bodies.

buffalo gnat biting someone

📸 by D. Sikes

Clusters of small, red bumps (often with halos around them) on your dog’s belly, folds of skin, or paws are often caused by fleas. Small, black pepper-like spots also indicate that fleas are the likely culprit. Your dog may also be licking or scratching a lot and may even have lost some hair or fur in the bite area. You can treat these naturally or with a vet-recommended medication.

A tick bite will be small and red like the one you might get from a mosquito. It may also be encircled by a red ring. If you think your dog has been bitten by a tick, check to make sure it’s not still on your dog. Removal of the entire tick as soon as possible is imperative.

👉 See our bug bite guide for tips on the treatment of tick bites. 

Black flies 101

Black flies live around flowing water like streams and rivers. Here they lay eggs and the larvae attach to rocks before emerging as flying adults.

They’re also commonly found on and near farms or in wooded areas and lowlands. If your dog has been near any of these environments, the greater the likelihood the bite that you’re looking at came from a black fly.

They tend to be most active in humid, wooded regions during the summer months. But can be found year-round in semi-tropical regions.

How to soothe and treat fly bites on your dog’s skin at home

Even if a fly bite isn’t life-threatening, it can still bug your dog. Scratching and licking irritated, itchy skin will add to the misery.  Here’s how to treat these bites:

First, you’ll want to start by carefully cleaning the area with warm, soapy water. Be gentle, as this area may be sensitive for your dog. If the wound has scabbed over, you may need to lightly press a warm compress on the scab to soften it before cleaning. Then, apply an ointment or even a paw balm on the wound for healing. Keep your dog indoors for a bit to ensure it doesn’t get dirty or the ointment doesn’t rub off. 

  • Oatmeal baths
  • Ice the bite with a cold pack
  • Hydrocortisone
  • Epsom salt
  • Applying a baking soda paste

🚨 Avoid using calamine lotion on your dog, as zinc is toxic to dogs.

When to call your vet

If the bites don’t improve or look worse in a few days or your dog won’t stop itching them, call your vet for treatment advice.

Additionally, there are four types of common allergic reactions that your dog could have after an insect bite or sting. Only two are life-threatening.

  • Hives (Urticaria). These are annoying and itchy, but they’re not life-threatening.
  • Allergic dermatitis. Your dog will have itchy, flaky skin.
  • Edema. You’ll notice significant swelling in the face or throat. It’s easily treatable with an antihistamine injection. It’s fatal when the swelling impairs your pup’s ability to breathe.
  • Anaphylaxis. The most severe type of allergic reaction can be fatal without treatment. Symptoms can reach a life-threatening stage in as little as 20 minutes.

Signs and symptoms of a life-threatening allergic reaction

If you see any combination of the following symptoms, consult a veterinarian right away:

  • Hives or swelling in areas other than the bite mark is a major sign of anaphylaxis
  • Vomiting
  • Diarrhea
  • Dizziness or disorientation
  • Seizures
  • Wheezing or trouble breathing
  • Weakness
  • Excessive drooling

How to keep flies off your dog

Since flies are widespread geographically and very active during certain times of the year in some places, it’s not always possible to avoid them. Here are some tricks to keep their bite count to a minimum.

  • Keep your dog’s coat and skin clean — It’s good for general health maintenance, too.
  • Clean pet waste in your yard — This includes any uneaten food scraps and rawhides.
  • Don’t overfill trash cans — This goes for recycling containers, too.
  • Cover any compost bins — This keeps flies from accessing organic matter that they’re attracted to.
  • Avoid walking at dusk, dawn, and during hot mid-day hours — These times are when black flies are most active.
  • Stay away from shady, densely vegetated areas — Forests are prime habitat for black flies and other insects.
  • Cover your dog’s ears with a light-colored, folded bandana — This creates a barrier to a sensitive area on your dog that black flies are attracted to. You can even spray the bandana with one of the safe insect-sprays listed below beforehand.

Cash wearing his fly bandana 😍

Don’t use human bug sprays on your dog

Before you reach for a repellent, consider that products containing Deet and other insecticides carry risks. These chemicals are absorbed through your dog’s skin and can be ingested when your pup licks their fur.

Essential oil sprays may pose similar problems and some — like cinnamon and citrus — are poisonous to dogs and cats. There’s also not much scientific evidence about the potential impacts essential oils may have on your dog.

Here are some of our most favorite low-toxicity, dog-safe bug sprays that get a thumbs-up from vets: