GUELPH -- Some dog owners in the Waterloo Region have been spotting bulls-eye-shaped bite marks on their pets, which could be caused by black flies.

But while they might look unsightly, black fly bites are mostly harmless for dogs, experts say.

Guelph resident Ryan Mueller found red bite marks on his dog Packer's stomach. His vet told him they were likely from black flies.

"It was a total freak out. I'm stressing, I'm worried," Mueller said. "Full-blown dog parent mode, what do I do, my kid is in trouble."

The Royal Ontario Museum's senior entomologist said we're right in the peak of black fly season, adding the bugs are more common in northern Ontario but can also be found in the south near running streams of water.

"Black flies are actually ambiguous, you can even find them in certain streams in Toronto," said Douglas Currie.

Lately, Guelph's Highway 24 Veterinarian Clinic has been getting an influx of calls from dog owners who have found similar bites – but not necessarily from black flies.

"They are harmless," said Dr. Dana Dolinsek at Highway 24. "They are a little bruise, they're from the bite of a fly."

Dogs may also get bite marks from small flies in tall grass.

The spots are sometimes shaped like a bullseye, so to the untrained eye, they can be mistaken for tick bites.

But black fly bites are not a health risk.

"They really don't cause much discomfort to the dog and they typically will just heal up in a little bit of time," Dolinsek said.

Dolinsek said it's important for dog owners to use flea and tick medication during the warmer months, which significantly decreases the risk that any bites will impact their health.

For Mueller, he's just glad his best friend Packer has since recovered.

"The last thing you want is somebody that you care and you love like your puppy to have to go that route," he said.