Decoding Canine Skin: Understanding Bumps and Lumps on Your Dog’s Skin

Last updated:
November 20, 2023
a black dog directly making eye contact with the camera lens in an outdoor

Understanding your dog's skin is essential for every pet parent. Just like humans, dogs can experience various skin issues, and sometimes it can be a bit confusing to distinguish what's normal from what might need attention. In this post, we'll explore the fascinating differences between canine and human skin and shed light on the different types of bumps and lumps that your beloved furry friend may develop.

Basics of dog’s skin

Your dog’s skin works differently than human skin—in more ways than just having fur that covers their whole body. 

The skin of your dog’s body has a lot of jobs to do. For one, it’s the main barrier that protects their insides from things on the outside. It creates a protective barrier against the environment, regulates your dog’s temperature, and gives them a sense of touch. Your dog’s skin is a huge and important factor of how their body operates, and makes up 12-24% of your dog’s body weight.2 

The epidermis is the outermost layer of the skin; it is composed of multiple different types of cells that have multiple different purposes. 

Keratinocytes are skin cells that create the protective layer of skin that is constantly being renewed in a process called keratinization, this is when the top layer of dead skin cells are shed and replaced continuously by new cells from lower layers.2 The turnover rate of these cells is different depending on many different factors—nutrition, hormones, immune cells, genetics, etc.—but on average the canine turnover takes about 20 days, compared to a human’s rate of 28 days.2,1 Melanocytes are located at the bottom of the epidermis and are the cells that produce the skin and hair coloring pigment called melanin. Langerhans are skin cells that are parts of the immune system, and they are an important part of the skin’s response to foreign substances that create rashes when exposed to irritating materials. Markel cells are the cells in the skin that give your dog a sense of touch. 

In addition to the cells that make up the epidermis, there are also skin appendages that work alongside the epidermis cells and cover tasks that the skin can’t maintain on its own. Skin appendages include nails/claws, hair follicles, and oil glands. 

It's widely understood that a dog's hair growth operates quite differently from that of humans. Unlike human hair, which grows as individual strands and continues to grow indefinitely, a dog's hair grows in cycles, forming bundles. When a dog's hair reaches a specific length dictated by its genetic makeup, it ceases to grow and eventually sheds. Dogs with continuously growing fur, like poodles, have fur more like human hair which is why they do not shed as much as other breeds. Now, when it comes to maintaining that shiny and healthy coat, oil glands—also known as sebaceous glands—play a significant role. These glands are distributed generously near a dog's paws, the back of their neck, rump, chin, and tail region. They produce an oily substance called sebum, composed of fatty acids. This sebum is crucial for keeping the skin soft, moisturized, and flexible, giving the dog's coat a lustrous sheen, and providing some natural antibacterial protection.

A dog's coat serves as the outermost protection for their body. This coat not only keeps their skin supple and lustrous but also has essential antibiotic properties, providing a vital shield against various environmental threats

Common non-cancerous bumps on skin

Just like we humans get freckles and moles, our furry pals can also develop their version of 'blemishes,' which are often non-cancerous bumps on their skin. 


A hematoma is a bit like a raised bruise you might get when you bump your leg. For your furry friend, it can be painful to the touch, and it usually occurs after some sort of direct injury to that part of their body. Although hematomas themselves aren't typically a major worry for your dog's well-being, they could be a sign that something more serious is happening beneath the surface. There might be an unseen problem, like a hidden bone fracture, under that swollen area. To be on the safe side, it's a good idea to have a veterinarian examine it and ensure there are no underlying issues. This way, you can be sure that your dog is in the best possible health.3


Papillomas, commonly known as warts, are benign growths found on a dog's skin, often resembling cauliflower. These growths are typically caused by a contact virus passed from one dog to another, making them more prevalent in dogs that engage in playgroups, frequent dog parks, or spend time in daycare. They tend to appear on the lips, inside the mouth, and around the eyes. While some papillomas can cause difficulties with eating, most of these infections resolve on their own within a few weeks, although some may persist for months. If a papilloma is causing significant discomfort or eating issues for your dog, your veterinarian might recommend surgical removal.3,4

Warts, or papillomas, can result from various factors, including viral infections, vaccination sites, and aging. Younger dogs often have developing immune systems that can naturally heal warts, whereas older dogs may require removal by a vet. In addition, it's essential to keep your dog away from other dogs if they have a papilloma to prevent the spread of this viral infection during playtime.


Papules are tiny bumps that usually pop up near a hair follicle and can happen because of an allergy or a small infection. Usually, once you get rid of whatever caused the allergy, they'll disappear by themselves. But if you're not sure if those bumps are papules, it's a good idea to visit the vet. They can examine your dog and might even do an allergy test to figure out what's causing those bumps to appear.3

Histiocytoma/Button Tumors

Histiocytoma is a kind of non-cancerous tumor that forms on the skin within certain immune cells called histiocytes, which aid in fighting infections. These tumors often disappear by themselves within a few weeks, but in some cases, your vet might suggest removing them if they cause discomfort for your dog. They are often nicknamed "button tumors" and are more common in young dogs under 2 years old. Some dog breeds, like English bulldogs, Scottish terriers, greyhounds, boxers, Boston terriers, and Shar Peis, are more likely to develop histiocytomas.3,4

Nipples on male dogs

Male dogs indeed have nipples, just like their female counterparts. These little bumps are not a cause for concern; they're a natural part of a dog's anatomy. Nipples develop during a dog's early embryonic stages, and their number can vary. Male dogs typically have fewer nipples than females. While nipples can sometimes become more noticeable in older dogs or due to weight gain, they're not a sign of any skin problem or health issue. It's essential to understand that these nipples are entirely normal. So, if you happen to spot them, rest assured that there is nothing to worry about.5

Skin tags and dog acne

Dogs can develop skin tags and even acne at times, much like humans. These common occurrences are generally nothing to worry about. Skin tags are small, soft growths that usually hang from the skin.6 Acne, on the other hand, can lead to pimple-like bumps often around your dog’s muzzle area.7 In most cases, these are benign and won't cause any harm to your furry friend. However, it's essential to keep an eye on them. If you notice any significant growth in size or any unusual changes in color, shape, or texture, it's a good idea to get in touch with your vet. While these issues are often harmless, it's always better to consult a professional if you have concerns. Your vet can provide guidance and ensure your dog's skin remains healthy and comfortable.

Cancerous bumps on a dog’s skin 

Discovering a concerning bump on your furry companion's skin can be a cause for worry, and it's essential to recognize the signs of potentially cancerous growths. In this section, we'll delve into the different types of skin bumps in dogs that might be cause for a closer look. 


Melanoma is a type of cancerous tumor that originates from cells called melanocytes, which are one of the main types of skin cells in a dog's epidermis. These cells are responsible for producing pigment. Melanomas can vary in color, appearing pink or non-pigmented, or they might be dark, depending on the dog's skin tone beneath their fur. The most frequent locations for melanomas to develop in dogs include the mouth, eyes, nail beds, and other areas on the skin. Oral melanoma, which occurs in the mouth, is the most common type and tends to be aggressive with a high likelihood of spreading. To treat melanoma, a combination of approaches is often used, including surgery, chemotherapy, radiation therapy, and immunotherapy.

You can read more about Melanoma here. 


Hemangiosarcoma is a type of cancer that arises from the cells lining blood vessels. These tumors can occur in various parts of the body, with the most frequent locations being the dog's heart, spleen, and skin. Regrettably, visceral (internal organ) hemangiosarcoma is typically detected only after it ruptures, leading to an emergency situation involving severe internal bleeding that can quickly become life-threatening if not promptly treated. The typical approach to treatment involves addressing the internal bleeding, performing surgical removal of the affected spleen, and then administering chemotherapy to manage the cancer's spread.

But hemangiosarcoma of the skin is very different. These are small, round, spots on dogs’ skin generally secondary to sun exposure. These red spots most often occur on the abdomen where there is less fur. These tumors can appear like blood blisters and may bleed. Surgery is generally curative unless the lesion is extending deep into other tissues like the muscle or if there are too many lesions to surgically remove.

You can read more about hemangiosarcoma here. 

Mast Cell tumors

Mast cell tumors stand as the most prevalent type of skin cancer in dogs, displaying a wide range of appearances depending on their location, development, and timing. These tumors can emerge both on the surface of your dog's skin, visible through their fur, or beneath it, concealed by the fur. They typically possess a solid, firm texture and rounded bumps. Mast cell tumors are called the great pretenders because they can look like anything from a classic hairless, firm, round lump to a soft, ill-defined swelling under the skin.

Since mast cell tumors are a form of skin cancer, professional intervention is crucial. Your veterinarian will likely suggest the surgical removal of the affected tissue, along with a small margin of normal surrounding tissue to ensure the complete removal of all cancerous cells. When detected early, this approach is highly effective, allowing your furry companion to recover swiftly and resume their usual activities.

You can read more about mast cell tumors here.

What to do if you find a bump on your dog’s skin 

When you notice a bump on your dog's skin, the vet may perform different tests to determine its nature and severity. One common test is Fine Needle Aspiration (FNA), where a small needle is used—similar to those used to collect blood— to extract cell samples from the bump. These cells are examined under a microscope to identify any cancerous properties and determine the type of lump.

If FNA doesn't yield a clear diagnosis, your vet might opt for a biopsy, which requires a small surgery. The biopsy involved the removal and close examination of a portion or the entire lump in a laboratory. If the bump contains fluid, the vet will extract the fluid and analyze it molecularly.

Once the test results are in, your vet will develop a suitable plan of action, which may range from observation and monitoring changes in the lump's size to recommending antibiotics or surgical removal for more serious cases.

While not all lumps are cause for immediate concern, it's always wise to consult your vet. Even if you believe the bump will resolve on its own, don't hesitate to reach out to your vet. Many vet clinics provide an associate email address, allowing you to inquire about your pet's condition and even share photos. If the lump is potentially problematic, the clinic will guide you on whether a physical appointment is necessary. Your dog's health is a top priority, and vigilance is key in ensuring their well-being.

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