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How a Dog's Carnassial Tooth May Cause Swelling Under the Eye

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Learn more about the carnassial tooth and how it can cause swelling beneath a dog's eye.

Learn more about the carnassial tooth and how it can cause swelling beneath a dog's eye.

What Causes Swelling Under a Dog's Eye?

If your dog develops swelling under his eye, you may chalk it up to being some sort of temporary eye problem, or perhaps you may assume it's just an insect bite. Yet, a day later, and the day after that, the swelling is still there, and you now also notice some drainage. What gives?

It's very common for dog owners to be fooled when they see this type of swelling. Whether there is a draining pustule under the dog's eye, a lump or an actual abscess, dog owners are often perplexed by it. It's especially perplexing when the area seals over and the swelling is gone for a bit, only to come back after a while, explains veterinarian Ron Hines on his website. Some dog owners ignore the problem since their dogs continue to act happy and healthy, so they wait to mention it when they bring their dog to the vet for some other problem.

The Problem May Be an Infected Tooth

So what may be going on with these dogs? Is that facial swelling just below the dog's eye some medical mystery? If it's not an eye problem or an insect bite, what is going on? Respected veterinarian Dr. Ronald Hines has a possible explanation: an infection that has spread from an infected tooth.

The owners often doubt me when I tell them that the actual problem is in the dog’s mouth. What has happened is that an infection has spread from an infected fourth upper premolar tooth."

— Dr. Ronald Hines

The dog's upper carnassial tooth is the largest tooth and has 3 roots. All rights reserved.

The dog's upper carnassial tooth is the largest tooth and has 3 roots. All rights reserved.

Understanding a Dog's Carnassial Teeth

Have you ever watched your dog carefully when they chew a bone? If so, you may have noticed how, at some point, they'll turn their head and use their back teeth to cut through the meat or crush the bone. When they do that, they are using their carnassial teeth.

Function of the Carnassial Teeth

What are a dog's carnassial teeth? If you take a look at the word carnassial, it comes from the French word "carnassier" which stands for carnivorous. Carnassial teeth are commonly found in meat-eating animals. Also known as shearing teeth, their main function is to allow the dog to crack bones and shear through the flesh, tendons and muscles of their prey.

Your dog may not need these teeth as much as they might have in their past as a hunter, but you'll still see them put them to good use when they're gnawing on a bone, chew toy or raw meat if they're on a raw meat diet.

Location of These Teeth

Where are the carnassial teeth exactly located? Well, consider that adult dogs have 42 teeth, consisting of 6 incisors, 2 canines, 8 pre-molars and 4 molars in the top jaw, and 6 incisors, 2 canines, 8 pre-molars and 6 molars in the bottom one. Carnassial teeth consist of teeth pairs that work together to provide that strong shearing action carnivorous predators are known for. They comprise the dog's fourth upper premolar and the first lower molar.

These teeth are known for having self-sharpening edges that work together when the dog is chewing. Basically, when the dog chews laterally with his head tilted sideways, the inside of the dog's fourth upper premolar aligns with the outer surface of the first lower molar, providing potent shearing action. Yes, just like shearing blades!

This dog is using its carnassial teeth to chew on this log.

This dog is using its carnassial teeth to chew on this log.

How Infections Develop in Carnassial Teeth

When things go well, the dog's teeth shear through meat, muscles, and tendons; they even crack bones with no problem. However, sometimes things don't go as planned. As dogs age, their teeth may weaken and putting tremendous force on them with strong shearing action, may predispose them to fractures. All it takes is for the dog to chew on something that is harder than the actual tooth.

Things dogs chew that may be culprits for a fractured carnassial tooth include bones (raw or cooked), cow hooves, nylon toys, rocks and the bars of cages, explains Daniel T. Carmichael, a veterinarian specializing in veterinary dentistry. However, things may also go awry when a dog sustains injury to the teeth through a vehicle accident, being kicked by an animal or even catching a flying object roughly with the mouth.

What Happens When a Tooth Gets Fractured

When the upper fourth premolar gets fractured, bacteria may enter through the gap and move its way along the carnassial tooth's long roots and then create an infection pocket that may generate an abscess in the dog's facial area, right under the dog's eye.

How Do Veterinarians Treat Carnassial Teeth Infections?

Taking antibiotics for this type of abscess may sound like a good idea, but it's only a temporary measure. Since the problem tooth is still in the mouth, the problem is likely to recur sooner than later. The only way to fix the problem is to extract the problem tooth, or if you are lucky to have a vet specializing in veterinary dentistry, there may be chances the tooth can be restored through a restorative procedure such as a root canal.

Other Possible Causes of Swelling

Of course, swelling under a dog's eye may also be due to other conditions. An insect bite, a severe allergic reaction, an animal bite and tumors may be other culprits. If your dog has developed swelling under his eye, see your vet for proper diagnosis and treatment.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

Question: My 12 year old pom just started getting swelling under the right eye about 4 hours ago with a little bit of puss coming out of the eye. It's possible that it is being caused by an issue with the carnassial tooth, but the video never says anything about the breath. My dog's breath is so bad that I really think something is rotting in his mouth and has been this way for about a year. But the swelling just started. Can that still all be related?

Answer: A carnassial tooth infection is just that: an infection that gets progressively worse. Therefore, it's normal for the breath to have a bad, rotten smell. There may be also other concomitant rotting teeth in the mouth which may give off the smell, considering that your dog is a Pomeranian and small breed dogs have small mouths with overcrowding teeth which predispose them to tartar accumulation and periodontal disease. An abscess is an infection that has progressed to invade interior areas of the body, hence the hallmark swelling under the eye.

Question: Does an abscessed tooth hurt? My dog doesn’t act like he’s in pain.

Answer: An abscessed tooth is painful whether in humans or animals. Dogs though do not always communicate their pain in obvious ways because it shows weakness and weakness in the the wild could have meant becoming prey. Your dog may be showing pain in subtle ways that are not recognized. This may include licking paws, lip smacking, drooling, panting, breathing faster or just not chewing on that side or dropping kibble.


Sheena999 on June 15, 2020:

My 16 year old chihuahua has a rotten fang tooth. Vet gave antibiotics but said she can’t give them all the time. She was a apprehensive to take it out. I’ve been putting coconut oil on it twice a day now for 6 months and it kept it at bay but now she has a swelling under her eye? I’m sure by reading your comments now that this is due to her tooth. But my problem is. I’m scared of putting her under an anaesthetic at her age? Can someone please advise? My poor girl

Sunni Porter on March 14, 2018:

Thx u very much for this info. It was really helpful. It’s nice to see that u are trying to help people fix the main problem instead of putting a band aid over it.

Adrienne Farricelli (author) on March 26, 2016:

Thanks AliciaC and Suhail and my dog for stopping by. Hopefully, it will be helpful for many dog owners!

Suhail Zubaid aka Clark Kent from Mississauga, ON on March 26, 2016:

This is going to be a great resource hub for any contingency relating to my dog. I think you have done a wonderful job in writing and putting together all the information in a way that is easy to read and remember.


Linda Crampton from British Columbia, Canada on March 25, 2016:

Thanks for sharing this useful information. I'll keep it in mind in case my dogs develop the problem that you describe.

Adrienne Farricelli (author) on March 24, 2016:

Thanks DDE, my friend had a husky with this swelling under the eye problem and we saw several dogs with this at the vet so thought to write about this to spread awareness.

Devika Primić from Dubrovnik, Croatia on March 24, 2016:

Dogs are amazing pets and need proper care. Your helpful hubs are interesting and have useful tips.