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Ask a Vet: Why Do Dogs Have Bumps on Their Lips–Is It Normal?

Dear Doctor,

I noticed a couple of days ago my dog has some funny looking bumps on her lip. She has an appointment with the vet next week but I’m so worried now! What do you think it could be?

–Sarah 

Hi Sarah,

Thanks for sending in this question. I wish I had a straight answer for you, but dog lip bumps can come from lots of different things. Some are completely innocent and others need focused veterinary treatment. 

The main causes of dog lip bumps include allergy, virus, bacteria, fungus, parasites, chronic abrasion, benign tumors and cancerous tumors. 

Dog’s lips take a lot of abuse. They come into contact with some very unsavory substances and they’re constantly being rubbed and soaked with saliva. They also have plenty of immune-system cells since they are likely to come into contact with infectious agents before any other part of the body. 

Let’s talk about some of the specific causes of bumps on a dog’s lips and mouth. 

Why Do Dogs Have Bumps on Their Lips? 

There is one type of bump on a dog’s lip that is 100% normal. 

On the edge of a dog’s lower lip, you’ll find about 15 little projections or bumps that are only about a ⅛-¼ inch tall. (2) These are called macroscopic papillae or lip fimbriae. They look like a serrated knife but the lip nubbins are soft and hairless. 

No one knows for sure if there is a purpose for these lip bumps. You’ll notice lip fimbriae more on dogs with droopy lips like Bulldogs, Mastiffs and Cocker Spaniels. 

Why do dogs have bumps on their lips?
Normal bumps on a dog’s lower lip

Abnormal Bumps on a Dog’s Lips

Lumps and bumps on dog lips are pretty common considering they love to chew and aren’t exactly the most hygienic creatures to walk the earth. Their teeth also rub on their lips, causing thickened areas to form which sometimes become very prominent.. 

It is often very difficult to tell a benign lip bump from a malignant one. Your vet will most likely want to do a biopsy of the affected area before making a diagnosis.

The following are some of the more common causes of abnormal lumps and bumps on a dog’s lips and perioral tissue…

Chin Acne

Did you know dogs can get acne? The more technical term is muzzle folliculitis and furunculosis. It looks like red bumps on the chin and lips. 

Dog chin acne is most common in young, short-haired dogs. I’ve seen it in various bulldog breeds as well as Mastiff-type dogs most frequently. The short hairs of these types of dogs seem to irritate the skin of the chin and lips when the dog rubs the area during normal activity. 

Chin acne can overlap with the next dog lip malady, cheilitis…

Lip Fold Dermatitis

The medical term for lip fold dermatitis is cheilitis. The typical lesions are hair loss, crusting, oozing, swelling and sometimes pain or itchiness. Many dogs with cheilitis also seem to have increased bad odor around their mouth from the sores. 

The cause of cheilitis in dogs often involves hypersensitivity or allergies (environmental or food) (1), chronic trauma from teeth, and chronic moisture due to heavy/floppy lip anatomy allowing saliva to leak onto the skin. 

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Parasitic and Fungal Infection

There are a few parasites that can cause lesions on a dog’s lips. 

Demodicosis is caused by a microscopic skin mite. Some people call the disease “red mange.” It causes hair loss, bumps and sores in affected dogs. Sometimes these lesions show up as bumps on a dog’s lips that look similar to those found in other diseases. 

A single-celled protozoan organism in the Leishmania family causes Leishmaniasis in dogs and is most common in Mediterranean countries. The infection often causes sores around the mouth area but can affect other parts of a dog’s body including the heart, lungs and stomach. 

Ringworm is a skin disease caused not by a worm but by a fungus. It’s not uncommon for dogs to get ringworm infection on their muzzle since the fungal spores are found in soil dogs like to root in. A classic ringworm lesion looks like a hairless, slightly raised red bump and can show up on a dog’s upper or lower lip, or any part of their body. 

All of these parasites need to first be diagnosed by a vet and then treated with an effective protocol of medication.

dog oral papilloma
A viral papilloma on a young dog’s upper lip.

Canine Oral Papillomas

Canine oral papillomas are more common in young dogs under the age of 2 years but can affect dogs of any age. The virus is contagious between dogs and most of my patients seem to pick it up when they play closely with other dogs in a dog park, doggy daycare or boarding. 

These dog warts frequently grow on the muzzle, lips and mouth of an affected dog. Usually, they’re 2-5 mm in diameter and are attached to the skin by a narrow base. If you look closely, you’ll notice a warty bumpy surface to them, kind of like the surface of a head of cauliflower. 

Although the papilloma virus is contagious to other dogs, most clear the infection with no treatment within a few weeks to months. 

Oral Cancer and Benign Tumors

Now we come to the more serious section of this discussion: oral cancer and benign tumors. 

Dogs can get skin cancer on their lips as well as various sorts of tumors on their gums adjacent to the lip. It can be very difficult to tell if a tumor or growth is cancerous or non-cancerous without a biopsy. 

Some of the more common tumors seen in a dog’s mouth or on their lip include

  • Malignant melanoma 
  • Squamous cell carcinoma 
  • Fibrosarcoma
  • Cutaneous lymphoma
  • Mast cell tumors
  • Benign histiocytoma
  • Epulis 

As soon as you notice anything that looks like a bump in your pup’s mouth, have your vet check it right away. Quick action may save her life. 

Summary

There are normal and abnormal bumps on dog lips. And even among the abnormal bumps, only some of them are very dangerous. 

The bottom line is that every bump on your dog’s lips or mouth should be taken seriously. Ask your vet to examine your dog right away and be ready to follow up with diagnostic testing. 

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References

  1. Doelle, M., Loeffler, A., Wolf, K., Kostka, V., & Linek, M. (2016). Clinical features, cytology and bacterial culture results in dogs with and without cheilitis and comparison of three sampling techniques. Veterinary Dermatology, 27(3), 140-e37.
  2. Evans, H. E., & De Lahunta, A. (2013). Miller’s anatomy of the dog-E-Book. Elsevier health sciences.

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