Rugal Folds Are the Cool Feature Every Dog Has (But You've Never Heard Of)

Have you ever had a look inside your dog’s mouth? I mean, had a really good look? If you have, you may have spotted small, bumpy ridges running all along the edge of your dog’s lower lip. It can be quite a surprise the first time you notice them, but before you panic thinking they’ve grown extra teeth, let us assure you that these bumps are totally normal. They’re called rugal folds, and we‘re going to take a look at exactly what they are and when we need to pay extra attention to them.

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What are rugal folds? 

These bumpy ridges along the lips are called rugal folds, rugae or lip fimbriae. Rugae are found in various places in dogs, including the lips, the hard palate on the roof of their mouth and their stomachs. They are perfectly normal and can come in a variety of sizes, shapes and colours, all individual to your particular dog. The rugal folds on the lips are made of the same non-keratinised epithelial cells as the surrounding lip, just with extra rounded peaks that look like teeth or a blunt serrated knife.

Why do dogs have rugal folds? 

Rugal folds have slightly different roles depending on where they are in the body, but generally, they give a greater surface area for whatever function that organ provides. For the lips, they provide extra grip for holding food when eating, acting much like a conveyor belt as the lip muscles contract, pulling the food in, very handy! These ridges also help protect the gum by providing a cushion between the upper teeth and the lower gum. On the hard palate, the rugal folds also aid with eating and drinking water. Whereas the rugal folds in the stomach help by creating more surface area, allowing the stomach to stretch and enlarge, and give a greater surface area for the absorption of nutrients.

Are rugal folds normal? 

Rugal folds are completely normal, even if they look weird at first. As all individuals are different, your dog’s lip rugal folds may not look the same as other dogs. They can have a variety of shapes and sizes, but usually, if your dog is bigger, then the rugal folds are bigger as well. Some dogs have big floppy grins, where the rugal folds are more obvious as they curl out away from the mouth. Some smaller dogs have only the slightest of small bumps as their rugae. The skin around dogs’ lips can be a variety of colours depending on the surrounding local area. The rugal folds are typically the same colour as the surrounding lip tissue, so they can appear pink through to black or consist of patches of either.

Rugal folds vs concerning lip bumps 

While lip rugal folds can vary in size from dog to dog, they should be uniform along the lip, starting as larger on the outer edge and tapering down to a smooth lip. It’s important to know what is normal for your own pup so you can spot any changes if they occur.

You should get your vet to check your pup out if you spot any changes in size, colour or texture of individual bumps. This could mean your pup has some inflammation or infection, as dogs can bite their lips just the same as we can. They can also cause trauma to their lips by chewing on sticks and other similar items. Any colour changes or growths that pop up along the rugal folds should be checked by your vets as both benign and sinister lesions can occur here.

A common lump seen along the lips are viral oral papilloma warts in younger dogs. These are benign, cauliflower-like lumps that are typically found around the head and lips and even inside the mouth. Immune-mediated diseases, skin conditions and cancers can also cause lip changes, so if you notice anything abnormal, it is best to make an appointment with your vet for a full examination.

Breed variations in rugal folds

Since dogs come in a variety of shapes and sizes, so do rugal folds. In particular, the rugal folds that cover the surface of the hard palate can be problematic for brachycephalic breeds such as boxers and bulldogs. In these breeds the folds are sometimes much deeper and cause inflammation called palatitis, which is caused by the entrapment of plaque and food debris. Signs your dog may have this inflammation include stinky dog breath, changes in eating behaviour or pawing at their mouths.

Larger dog breeds such as St Bernards or Great Danes can proudly show some fabulous lip rugal folds, as they flop out to the sides. All the better to spread that drool from!

Caring for your dog‘s lips and rugal folds

Rugal folds on the lip usually just require monitoring for any signs of injury or changes. But if you have a dog who is prone to skin conditions or lip fold dermatitis near the rugae, they may need extra attention. Keep the area clean and free of matted fur, as this could hide signs of irritation and trap bacteria. Only use dog cleansers that are safe to consume (many cleansers contain ingredients which can be toxic when consumed), or plain, cooled-down boiled water to wash the area if needed. And if you spot anything abnormal, let your vet know so your pup can be checked and you can talk through what’s causing it and next steps.

Resources

Margarita, Adriana, and Loïc Legendre. “Anatomy of the Brachycephalic Canine Hard Palate and Treatment of Acquired Palatitis Using CO2Laser.” Journal of Veterinary Dentistry, vol. 36, no. 3, SAGE Publishing, Sept. 2019, pp. 186–97.

Munday, John S., et al. “Papillomaviruses in Dogs and Cats.” The Veterinary Journal, vol. 225, Elsevier BV, May 2017, pp. 23–31.

Sa, Guoliang, et al. “Histological Features of Oral Epithelium in Seven Animal Species: As a Reference for Selecting Animal Models.” European Journal of Pharmaceutical Sciences, vol. 81, Elsevier BV, Oct. 2015, pp. 10–17. 

Saverino, Kelly M., and Alexander M. Reiter. “Clinical Presentation, Causes, Treatment, and Outcome of Lip Avulsion Injuries in Dogs and Cats: 24 Cases (2001–2017).” Frontiers in Veterinary Science, vol. 5, Frontiers Media, July 2018.