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Red Bump or Lump on a Dog? 7 Likely Causes

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dog with a red lump on skin

✔️Article written by a veterinarian & reviewed by Dr. Whittenburg, director, on Dec 15th 2022. View our editorial quality process.

It is a bit alarming to see a new raised red bump appearing on your dog’s skin – sometimes seemingly overnight. However, in my experience as a veterinarian, many red bumps and lumps are benign and nothing to worry about. But that doesn’t mean they can’t also be a sign that something more worrying can be happening with your canine friend (some red lumps can be cancerous). It is therefore important that you take action. In this article, we will review the most frequent red bumps or lumps in dogs – with pictures.

What Does It Mean if My Dog Has a New Red Bump?

A raised red bump on a dog is usually the skin’s way of showing inflammation. That inflammation could be due to a number of different reasons and may be accompanied by different signs, including itching or bleeding.

Red bumps may be small, large, singular, or numerous. Red bumps can be as benign as a wart or as terrifying as a cancerous tumor or lesion. Because of this, it’s important that any new red bumps that show up on your dog be checked by a veterinarian. Let’s look at the most frequent types of red lumps and bumps on dogs.

Seven Most Frequent “Red” Lumps and Bumps in Dogs

vet looking at dog

1. Warts or Skin Tags

Warts and skin tags are very frequent in dogs, especially as they get older. They are caused by an infection with papillomavirus. While they are typically a darker color, they may also appear pink/reddish. Warts and skin tags on dogs are most often benign. Occasionally, warts can become cancerous, so any wart that is a long-term issue or that changes in color/size/look needs to be investigated by a vet. See the image below for an example: wart on a dog

wart at the vet
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Skin tags are another benign growth in dogs that typically occurs as dogs get older. Skin tags are usually fairly small and the color of a dog’s skin. Occasionally, they can grow larger and become irritating for a dog.

skin tag on dog
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Treatment and prognosis: Most warts and skin tags won’t require treatment. Warts will typically go away on their own within a couple of months, and skin tags generally don’t get big enough to become problematic. However, either of these growths can become irritating depending on their size and location. Dogs may lick or chew on them until they bleed and become infected. If this is the case, these bumps may be removed with local anesthetic or cryotherapy. If you notice any change in the size and shape of your dog’s skin tag or wart, or your dog has a wart that’s been there for longer than 2-3 months, have it checked by a vet. Learn more: dog warts and skin tags

WATCH: 3 Important Tips To Care For an Old Dog [VET VIDEO]

2. Squamous Cell Carcinoma

Squamous cell carcinomas in dogs are fairly common, and they vary in their levels of aggressive cancerous behavior in terms or spreading. The red bump pictured below is one example:

squamous cell carcinoma on a dog's leg or paw
Red lump on a dog’s legenlarge

These types of malignant tumors are usually found on areas of skin that are bare, or have little hair, and are more common in dogs with light-colored skin. UV radiation from the sun can contribute to the development of these tumors. Squamous cell tumors in dogs can be raised lumps or nodules, or flatter areas of ulcerated skin. They can sometimes resemble warts.

Treatment and prognosis: The most common treatment for squamous cell carcinomas is surgical removal. It’s important to get all of the cancerous cells during the process to prevent recurrence, which can be difficult because these tumors may grow in areas like toes and legs that make closure hard. If the entire tumor can be removed, the prognosis is good. If not, the tumor may recur.

3. Mast Cell Tumors

Mast cell tumors come in very different shapes and sizes – including red lumps or bumps as pictured below. In healthy dogs, mast cells are a type of white blood cell that releases histamine in response to allergies and other irritants. Mast cell tumors are more often seen in middle-aged and older dogs but can affect younger dogs too.

lump looking like mast cell tumor

These old dog lumps are not always malignant, but it’s impossible to know which ones are and which aren’t without a fine needle aspirate or biopsy.

mast cell tumor on dog

Mast cell tumors can vary a LOT in appearance; usually, they’re a smooth, round growth visible on the skin. Other times they can look like a wart, or resemble a lipoma, and sometimes they are red in color. Some mast cell tumors are slow-growing, and others appear very quickly.

Treatment and prognosis: If caught early on, mast cell tumors have a high success rate with removal. If caught later, these tumors may spread to local lymph nodes and other organs, requiring surgical removal of the tumor as well as chemotherapy to get it under control. If surgery isn’t an option because of the location of the tumor, radiation may be used instead. For tumors located on the legs, there is a medication that can be injected into he tumor that results in its sloughing. Learn more in our article about “Mast Cell Tumors: a Veterinarian’s Guide for the Dog Owner” (including images).

4. Histiocytoma

histiocytoma red lump on dog skin

Histiocytes are cells that work surveillance for the immune system. Occasionally, especially in younger dogs, these cells can over-reproduce and create small, red lumps. This may be spurred on by previous injuries to the area or by insect bites or stings. These bumps are rapid growing but are benign and often actually go away on their own. Sometimes dogs may lick or chew at histiocytomas causing them to ulcerate and become infected.

Treatment and prognosis: Most histiocytomas will go away on their own within a few months. However, if your dog is bothered by it or has caused ulceration or an infection, surgical removal may be necessary. Antibiotics may also be needed to control the infection.

Important: It is usually not possible to diagnose a lump just by looking at it. The diagnosis of skin lumps and bumps often involves your vet taking samples and analyzing them under a microscope.

5. Melanoma

Melanoma tumors are dark and can be small, or large, flat, or raised. They can be either benign or malignant, so they shouldn’t be ignored.

melanoma growth
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If a dog has malignant melanoma, it’s usually an aggressive cancer that recurs even after removal and may spread throughout the body quickly, so the lesion needs to be surgically removed as quickly as possible. Only a veterinarian can tell the difference between a benign and a malignant melanoma by doing a biopsy. Most malignant melanomas in dogs grow in/around the mouth or in other mucus membranes where there is less hair, but they can also be found in other areas.

Treatment and prognosis: Malignant melanomas are very aggressive and prompt treatment is required for the best outcome. Surgery is required to remove the initial tumor and then radiation may be necessary to deal with any spread. Chemotherapy generally isn’t very successful.

6. Skin Rashes

Dogs may also develop red bumps due to allergies or other irritants. They may pop up with many small bumps or just a few larger bumps. The inciting cause may be an allergy to fleas, pollens, or chemicals in the environment. Red bumps can also be a sign of mites. The bumps may also be itchy, which may cause bleeding, oozing, and secondary infections.

flea allergic reaction

Treatment and prognosis: Most skin rashes in dogs are treated by dealing with the underlying cause. For allergies, removing that allergen from the environment or treating with antihistamines or anti-inflammatories is usually helpful. Mites will need treatment with an antiparasiticide. Secondary infection may require antibiotics. Learn more about red skin rashes in dogs.

7. Foreign Object

Any dog that’s out and about may come in contact with things that are sharp and prickly. Sometimes those things can become lodged in a dog’s skin, where they will become inflamed and develop a red bump. Grass seeds, thistle stickers, and slivers are common culprits. Dogs may lick at these bumps, causing them to become raw and ooze. They may grow very quickly and be quite alarming.

red bump on a dog's paw
Red lump on a dog’s pawenlarge

Treatment and prognosis: Removing the foreign object is usually all it takes to get rid of this kind of red bump. Sometimes those objects can be too small to see, so soaking in Epsom salts may be necessary. Antibiotics may be needed to control any secondary infection.

How Do You Know When a Red Bump or Lump Is Cancerous?

Cancer is the abnormal and rapid growth of previously healthy cells. Therefore, lesions or lumps that are growing rapidly or changing in appearance quickly on your dog’s skin may indicate a more sinister underlying cause.

A red color, as well as ulceration and a firm texture, are all common properties of a cancerous bump. The red bump on the picture below looks like a cancerous mass because of the red raw mass (however, it could also be a benign growth).

This does not mean that all red lumps and bumps are cancerous. It is usually not possible to tell if a red bump or lump is cancerous just by looking at it. However, below are some clues that can help raise suspicions:

  • Rate of growth: Cancerous bumps tend to grow more rapidly than those that are benign. They will grow into the surrounding healthy tissue, causing damage and inflammation. If a bump doubles in size over the course of a few weeks, then it’s best to schedule an appointment with your veterinarian as soon as possible.
  • Texture: Cancerous lumps are often firmer to the touch.
  • Shape: Due to their rapid and erratic growth, cancerous lumps tend to appear more irregular in shape.
  • Color: Red, black, or just generally ‘unhealthy’ looking lesions may be more malignant in origin.
  • Discharge: Oozing or discharge from the lesion may occur due to damage and death of the tissue in surrounding areas. While any lump can develop a secondary infection, sinister lumps are more prone to producing pus and bleeding.

Cancerous, or malignant, skin bumps can be small or large. They can itch or cause discomfort but may also not do either – and your dog may continue to act normal. This is why it is important to always consult with your veterinarian.

How Your Veterinarian Will Figure It Out

The diagnosis of skin lumps and bumps often involves your vet taking samples and having them analyzed by a veterinary pathologist. This process is known as histopathology. Exactly the same as in human medicine, histopathology is a very specialized discipline, so the samples will be sent to an external laboratory for analysis. Different sampling techniques can be performed including:

Fine needle aspirate – a needle with a syringe attached is inserted into the lesion, and a sample is taken by pulling back on the plunger of the syringe.

Biopsy –  a biopsy is a wedge of tissue that is taken from the lesion and then sent for analysis. This is performed under a general anesthetic and is the gold standard for getting a diagnosis of a skin lesion.

Related posts:

Images of Skin Problems in Dogs

Common Lumps and Bumps on Dogs


  • Dr Chyrle Bonk, Veterinarian

    Dr. Chyrle Bonk received her Master in Animal Science from the University of Idaho and her Doctorate of Veterinary Medicine (DVM) from Oregon State University in 2010. She has over 10 years of experience in small animal veterinary practice, working for a veterinary clinic in Idaho.

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