Black Fly Bites on Dogs? 6 Ways to Protect Your Dog From Black Flies, Horse Flies, Deer Flies, and Stable Flies

Maria | SYDE Road
10 min readAug 31, 2022

Are you thinking of staying in a yurt, glamping, camping, doing a farm stay, or simply heading to a dog beach for the day? Excluding winter camping, the annoying “Bzz! Bzz!” And “Ouch!” of insect bites are inevitable.

When we think of insect bites and harm, we think of protecting dogs from mosquitoes, tick bites, and heartworms.

But there are some insects we tend to forget — biting flies. If you’ve ever kayaked or canoed on a quiet lake or visited a Provincial Park’s dog beach for a day trip, then you’ll know just how painfully annoying biting flies are!

Today, we’re focusing exclusively on these nonlife-threatening but annoying fly bites on dogs.

You will find the culmination of all my research on fly bites below.

Please note that I am not a veterinarian nor am I an animal health care professional. This blog is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. Always seek the advice of your veterinarian with any questions you may have regarding the condition and/or the safety of your dog.

Which Flies Bite Dogs in Ontario?

In Ontario, the most common flies that bite humans and dogs are:

  1. Black Flies
  2. Deer and Horse Flies
  3. Stable Flies

Here’s an infographic summarizing what each fly looks like, its peak season in Ontario, its peak active time in a day, and where its favourite target areas are on our pooch.

Fly Bites on Dog Infographic. Infographic created by SYDE Road, contains information about the three common types of biting flies in Ontario, their key physical characteristics, a description of how fly bites can appear on a dog.

1. Black Flies

In Ontario, there are 63 different species of black flies (fun fact — there are 1250+ species known worldwide!).

Black flies are small — about 1–5 mm and come in varying shades of black, yellowish-orange, and brownish grey. They are mostly found in moving water.

Peak Biting Season: Adults tend to emerge and female black flies actively bite between mid-May to late June. Black flies are most commonly found near seasonal creeks and other freshwater sources like rivers.

Favourite Biting Time: Black flies tend to be most abundant on hot, humid, days.

Black Fly Bites on Dogs: Bites from a black fly typically appear as red rings or dots on the belly of your dog. Your dog isn’t normally bothered by these bites and the redness typically fades on its own without any treatment.

2. Deer and Horse Flies

These large flies (10–30 mm) are most well known to anyone who has ever ventured outside of urban areas in Ontario.

If you’ve ever been bitten by a fly and it felt like it took a chunk of your skin, then chances are you were bit by these large deer and horse flies.

With their knife-like mouth parts, their bites slash the skin to draw blood. Like the black flies, only the female flies draw blood.

Peak Biting Season: Deer and horse flies are most abundant during the summer months and are most often found around swamps, marshes, or the fringes of woodland areas.

Favourite Biting Time: Most are active during the day. These flies rely on motion to feed.

Deer and Horsefly Bites on Dogs: If deer flies or horseflies swarm your dog, you’ll likely hear them yelp, and see them suddenly twist and snap at the air. These bites hurt! Horsefly bites on your dog can cause small cuts or welts — most notably around the face, ears, and armpits. Some of the cuts may produce visible blood from the bite incisions but will typically clot in a few minutes. Scabs may remain over the next few days.

3. Stable Flies

Closer in size to a house fly (5–8 mm), these annoying stable flies tend to go for the ankle and feet. Even worse — both the males and the females will bite for a meal!

Stable flies, much like their name, tend to hang around livestock stables. Their favourite breeding grounds are rotting hay, grasses, or straws — really anywhere with some degree of decaying matter.

Paddlers and swimmers know these are persistent little buggers! Black flies can fly long distances too so chances are you’ll still see them around in the middle of a lake!

Peak Biting Season: Mid to late summer. Stable flies are found near wet, moist, decaying matter.

Favourite Biting Time: Most are active during the day. These flies rely on motion to feed.

Stable Fly Bites on Dogs: While stable flies tend to feed on larger domesticated animals like cattle and horses, these flies will also take the opportunity to feast on your dog too. Stable flies tend to target dog ears. To get a full meal — these flies will bite 4–5 times to get a full meal. Similar to the deer or horse flies, you may notice small cuts and some visible blood. Scabs may remain over the next few days.

Puppy Jack Russel Terrier is sitting in veterinarian examination room with stethoscope around it's neck

Treating Black Fly Bites on Dogs and Other Fly Bites

While most fly bites are irritating, and painful when they do happen, few have lasting detrimental effects that require a trip to the veterinarian.

Bright red spots from black fly bites, while distressing for most pet owners to see, tend to fade on their own without much treatment.

Now, you might be wondering, how long do black fly bites last on dogs? These bright red marks typically fade away after 48 to 72 hours.

Treating Horse Fly and Deer Fly Bites on Dogs

Bite wounds that draw blood from deer flies, horse flies, or stable flies, should generally receive basic wound care first aid — wash with clean water and mild soap to keep them infection free.

While the wounds are still open, it’s best to keep your dog indoors. If you’re planning on spending more time outside, or if your dog is going to go swimming with open wounds, you can protect the open wounds with a thin coat of petroleum jelly.

Much like our cuts too — be sure to regularly wash off the petroleum jelly and keep the open wounds clean to prevent infections.

When to See the Veterinarian if Your Dog Was Bitten by a Fly

In most cases, you don’t need to see a veterinarian for fly bites — injuries or red welts will typically heal on their own.

However, there are rare cases where, some dogs may experience allergic reactions, infections or other complications, so if you notice signs of:

  • Excessive itching
  • Oozing wounds
  • Vomiting
  • Seizures
  • Swelling
  • Wheezing or trouble breathing
  • Excessive drooling
  • Weakness
  • Diarrhea

Or if you’re just feeling extra precautious (or you aren’t sure if it’s a fly bite, a tick bite, or any other type of reaction) — don’t hesitate and book a trip to your vet!

Limone, a red and white corgi is held in mid-air by Maria - wearing a blue cap and red sweater. Limone's belly is showing. Limone and Maria are in a field near Peterborough, Ontario.

6 Ways to Protect Your Dog From Biting Flies

Since some flies rely on visual cues more than scent, and others rely on scent more than visual cues, some methods may be more effective than others depending on the type of biting fly you encounter.

If you’re heading somewhere where you think you’ll encounter both, chances are you’ll need to utilize a combination of methods below to protect your pet from these pesky biting flies.

1. Fly Repellent or Fly Sprays for Dogs

If you’re mostly concerned about protecting your dog from the common black fly and mosquitos, then consider purchasing a fly repellent or fly spray made specifically for dogs, horses, or ponies.

Most fly repellent sprays are made up of a combination of animal-safe essential oils and use scents to repel smaller biting insects.

From what I’ve searched, you won’t find fly repellent sprays in local pet shops like Petsmart, Ren’s Pets, or Pet Valu, but you’ll certainly have some luck sourcing some from horse supply shops!

Pleasant Ridge and Natural Pet Foods are two Ontario stores that I found that sell fly repellent products for dogs/horses. The popular: Absorbine Ultrashield Green Natural Fly Repellent is cheaper on both these sites than on Amazon too!


  1. Don’t expect to spray this only once during the day to protect your dog. You’ll need to thoroughly cover their bodies and fur AND apply it multiple times a day to keep the insects away.
  2. Ironically these fly repellents aren’t effective against stable flies, horse flies, or deer flies (biting flies that rely on visual cues more than scent).
  3. If your dog is already suffering from open wounds, has sensitive skin, or is suffering from other health issues — use caution and always ask your veterinarian ahead of time before applying anything on your dog.
  4. Most repellents are not recommended around your dog’s eyes, nose, or mouth area as they can irritate. You’ll also need to keep a watchful eye to prevent your dog from licking or grooming themselves after application

2. Dragonfly Clip / Dragonfly Wingman

100% the absolute cutest, most adorable option on this list! If you’re looking to scare or deter horse flies or deer flies, then consider clipping on one of their natural predators on yourself and your dog to keep them away!

Designed in Canada, and tested in Ontario cottage countries, this clip-on fake dragonfly mimics a real dragonfly to fool the horse and deer flies away (remember these types of flies are visual hunters, so a dragonfly visual is certainly a great deterrent!)

While I haven’t tested this myself, I have lingered in several Facebook groups and seen this proposed as an effective option from fellow dog owners!

I’d recommend checking out Canadian Tire to purchase a 2-pack (one for yourself and one for your dog!) — it’s the cheapest purchase online when compared to Lee Valley, Amazon, and strangely enough — even from the original makers Get Your Bug. You can get a single one for a cheaper price, but cost-wise per dragonfly clip — the two-pack from Canadian Tire really can’t be beaten!


  1. Not all dogs love having an attachment clip added to them — some additional training may be needed before
  2. It doesn’t protect from all bites — only helps to reduce. If you’re travelling in areas where there are a LOT of deer and horse flies, other users have reported that it doesn’t help much

3. Grease Vulnerable Areas

According to Northern Ontario Travel, oily skin makes it difficult for bugs to land and bite you, and bear grease was regularly used by indigenous people and early settlers as a form of bug repellent. Now while bear grease might not be easily accessible, other dog owners have found that rubbing a good amount of petroleum jelly or coconut oil on their dog’s vulnerable spots (think ears, muzzle, and near the eyes) significantly helped reduce the number of painful fly bites.


  1. It isn’t recommended to apply this when your dog already has open wounds as it can trap dirt and bacteria close to the wounds and cause infections
  2. Because you’re spreading something thick on your dog it’s a slightly messy affair

4. Apple Cider Vinegar Bug Repellent

If where you’re heading to is mostly filled with mosquitoes and black flies (and not stable, horse, or deer flies!) then you might be able to get away with using an apple cider vinegar spray to repel some insects. Apply the vinegar to your pup’s neck, collar, torso, tail, belly, or overall coat.

Drawbacks: You’ll need to regularly spray your pup with the vinegar spray to keep it effective meaning you and your pup will be smelling that strong vinegar scent too. For some, this scent might be off-putting enough to avoid this method.

5. Cover Up Your Pup

Physical protection against bites can help protect your dog from fly bites and other insect bites.

During my research, I found an interesting hood by Outfox. While this mesh hood was designed to protect canines against barbed grass seed penetration, it looks like a promising option to protect a dog’s head against fly bites too!

In addition, pups can wear insecticide clothing to provide physical protection against insect bites. Brands like Insect Shield create protective dog clothing pre-treated with dog-safe insecticide to repel and kill bugs before they bite. If you’re looking to reduce as many bites as possible looking for insect repellent dog gear can be incredibly helpful too!

6. Bring a Bug Tent

If you’re planning on hanging around outdoors and an onslaught of insects are barraging your poor pup, consider purchasing a portable, lightweight pop-up mosquito net. These tents are less than 3 pounds and offer a breathable open, bug-free respite for your pet to rest while relaxing on campgrounds.

Fly Bites on Dogs at Home? How to Prevent and Reduce Fly Bites

Is your dog getting bit by flies while at home or at the cottage? Ultimately, while you can do your utmost best to protect your dog from biting insects, the best way to keep you and your dog protected is to prevent flies from coming near your home.

Here are some tactics that can help reduce the number of biting flies (and therefore protect your pup from bites) that reach your pet and your home:

  1. Clear densely wooded and forested areas and/or avoid walking in these areas around your neighbourhood
  2. Keep your pet clean and well groomed. Flies can be attracted to the scent of dirty fur and be attracted to any poop hanging around their bum if they’re not a clean pooper!
  3. Remove nearby food sources and attractive breeding ground spaces (damp / decaying material like decaying leaves, rotting wood near the waterfront, fecal matter, or stagnant pools of water are popular locations)

Additional Reading

Hopefully, this post has helped you learn more about fly bites on dogs.

Here are some of the websites I referenced to learn more about fly bites on dogs if you’d like to learn more.

Happy reading!

More on the Blog

Like what you read? Here are some additional blog posts you may also want to read:

  1. Dog Owner’s Guide to Coyotes — Are Coyotes Dangerous to Dogs?
  2. Ouch! How Hot is Too Hot for a Dog This Summer?

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Maria | SYDE Road

A *mostly* dog-friendly content creator based in Toronto, Ontario Canada. Look forward to reviews, dog mom stories, and travel anecdotes.