When dogs suddenly have a lump under the skin, it is often a bulge, an abscess, or a lipoma. In some cases, hives and various tumors can also be behind it, which should be treated immediately.
For laypeople, these knots are usually difficult to distinguish from one another. For this reason, I recommend always consulting a veterinarian to be on the safe side with such complaints.
Below you will learn about the 9 most common causes and how to recognize them. You will also find out which breeds are primarily affected.
1. Grit Bag
A sac is a cyst that develops due to a blocked sebum gland. Doctors also speak of an “atheroma” here.
This lump under the skin can sometimes be as big as a chicken egg. It’s just a buildup of sebum, dead skin cells, and fat.
From the outside, the blocked sebaceous gland can usually be recognized by a black dot. Other classic symptoms of this are:
- Usually occurs on very hairy areas
- No sensitivity to touch as it is painless
- Size between a pea and a chicken egg
- Slowly increasing over days and weeks
- Plump, elastic, and can be moved
As dangerous and scary as this knot may look, it is usually harmless. It only becomes a problem when it becomes infected due to bacteria.
From a certain size, the groats bag can also restrict the dog’s movements. In such a case, it is usually surgically removed by the veterinarian.
When a sac forms in dogs due to a clogged sebum gland, this is usually recognizable by a lump under the skin. This knot is usually painless, relatively elastic, grows slowly and usually occurs in very hairy areas.
2. Abscess
When pus accumulates in the tissue in an encapsulated form, doctors also speak of an “abscess”. It is also colloquially known as “boil”.
In most cases, it is caused by a bacterial infection. This is especially true after bites from other animals, allowing pests to get in.
What is striking here is that the lump under the skin develops very quickly and causes pain. The most common signs include:
- Redness around the spot
- Light fever
- The dog keeps licking the spot
- Touch sensitivity
- Slight bleeding around the site
- Loss of appetite
For treatment, the lump is usually squeezed out by the vet and cleaned or surgically removed. The wound is cleaned and antibiotics are prescribed.
Depending on the cause and severity, further measures may also be necessary. However, such a boil does not have long-term consequences.
When dogs get a bacterial infection and pus collects under the skin, it usually shows as a reddish lump. Such abscesses are usually harmless but painful. Affected dogs also often get a fever.
3. Lipoma
If there is a benign skin growth in the fatty tissue, doctors speak of a “lipoma”. It is one of the most common types of tumors.
In principle, this fatty tumor can occur anywhere. The cause of this is still unclear. What is striking, however, is that the tumor can be moved easily and is soft.
However, it can sometimes feel hard if it spreads under a muscle. Other typical symptoms are:
- Sometimes several lumps under the skin
- No pain or tenderness to touch
- No redness or swelling
Bitches and overweight dogs are most commonly affected. Labrador Retrievers, Weimaraners, and Dobermans are also said to be at increased risk.
The only effective treatment here is to surgically remove the lump. The smaller it is, the easier it is to remove. This is where you should seek medical help.
A benign growth of fatty tissue in dogs can be known as a lump under the skin. Typically, lipomas are relatively soft, and painless, and are more common in overweight bitches. Sometimes there are even several of them.
4. Mast Cell Tumor
Mast cells are the body’s own cells that help fight off pathogens and allergens. If a tumor forms there, it is usually malignant.
Unfortunately, mast cell tumors are also one of the most common skin tumors in dogs. The cause of this is still unclear. However, the following breeds are more affected:
- German boxer
- Bernese Mountain Dog
- Boston terrier
- Labrador Retrievers
- Bull terrier
- Beagle
- Schnauzer
A mast cell tumor usually appears as a round lump under the skin and has a diameter of between 1-3 cm. Other typical signs are:
- Slight redness
- Resizing
- Hair loss at the site
- Surrounding swelling
The treatment depends on the degree of severity. In most cases, the tumor is surgically removed. After spreading, chemotherapy and radiotherapy can also be carried out.
Dogs with a mast cell tumor usually get a reddish lump under the skin that is between 1-3 cm in size. What is striking here is that the knot is rounded and can vary in size. The earlier this is diagnosed, the better the chances of recovery.
5. Histiocytoma
Histiocytes are cells responsible for immune defense. However, if these multiply abnormally, doctors also speak of a “histiocytoma”.
It is a benign skin tumor. The cause of this is still unclear, but young dogs and the following breeds are said to be more affected:
- Bull terrier
- German boxer
- Boston terrier
- American Pit Bull Terriers
- Labrador Retrievers
- Shar Pei
In most cases, a histiocytoma can be recognized by a red bump under or on the skin. Other typical symptoms are:
- Hairless Knot
- Under 2.5cm in diameter
- Bright Red Bubble
- Usually on the head or ears
- Sudden appearance
Typically, this tumor regresses on its own within 2-3 months. Surgical removal is only necessary if this does not happen or if it becomes too large.
When a histiocytoma forms in dogs, it is usually recognizable by a reddish and hairless lump under the skin. It is also noticeable that it develops relatively quickly and usually resolves itself within a few weeks.
6. Fibrosarcoma
A fibrosarcoma is a malignant tumor made up of connective tissue cells. In most cases, it develops on the dog’s legs or trunk.
Sometimes it also occurs in the nasal cavity and mouth. The underlying cause is still unknown here. However, the following breeds are said to be affected more frequently:
- Irish wolfhound
- Golden retriever
- Doberman
- Epagneul Breton
- Gordon Setters
But other large breeds of advanced age should also be found here more often. To a trained eye, it can usually be recognized by the following characteristics:
- Solid knot
- Bumps under the skin
- Slow growth
- May open and bleed
- Difficulty getting up
- Social distancing
- Sometimes several knobs
- Loss of appetite
For treatment, the tumor is usually surgically removed. Depending on the location and characteristics, however, this often only succeeds to a limited extent. In such cases, radiation therapy can help.
When a lump forms under the skin in the mouth or on the legs of large breeds of advanced age, it is often a fibrosarcoma. This malignant tumor usually grows very slowly and also affects the behavior of the dog.
7. Black Skin Cancer
Unfortunately, black skin cancer is one of the most common skin diseases in dogs. Doctors also talk about “melanoma” here.
Most often this occurs in the oral cavity or on the paws. The cause of this type of cancer is also unknown. It can usually be recognized by the following symptoms:
- Occasional pain
- Itching possible
- Mostly black
- Constant licking
- Weight loss
- Forms suddenly
- Inflammation is possible
Unfortunately, this type of tumor is very aggressive and spreads quickly. It is therefore not uncommon for the lump under the skin to increase in size quickly.
The earlier the tumor is diagnosed, the better the chances of treatment and recovery. If you suspect this, you should contact the vet immediately.
Black skin cancer in dogs, depending on the location and severity, usually causes a blackish lump to form under the skin. Under certain circumstances, it can also be skin-colored. It is also noticeable that it is suddenly there and sometimes itches.
8. Hives
Hives are a non-contagious skin disease that is usually caused by an allergic reaction. Other typical causes are:
- Insect bites
- Toxic plants
- Vaccinations
- Chemicals
- Allergens in the feed
- Insecticides
Typically, there is not just a lump under the skin, but numerous lumps at a close distance. Common signs of this are:
- Constant scratching
- Swelling of the face
- Dog drools profusely
- Usually 1-3 cm tall
- Partial redness
Since allergies are usually responsible for this, antihistamines are increasingly being used for treatment. An allergy test is also useful for prevention.
While these types of knots are annoying, they are usually not a cause for concern. They can only become dangerous if they make it difficult for the dog to breathe.
If dogs get several round lumps under the skin, then it is often hives. It is usually triggered by allergens. It is also typical that there is severe itching and sometimes reddening.
9. Squamous Cell Carcinoma
Squamous cell carcinoma is a malignant tumor of the skin and mucous membranes. In principle, it can occur anywhere. The following breeds are more likely to be affected:
- Labrador Retrievers
- Basset Hound
- Pekingese
- German boxer
- Norwegian Elkhound
- Golden retriever
- Poodle
Older dogs from the age of 6 are usually affected. Large, short-haired, dark-skinned four-legged friends who spend a lot of time in the sun are more likely to suffer from it.
At first, this bump under the skin often looks like a wart, but then it becomes progressively redder. Other typical features are:
- Ignition possible
- Severe redness
- Crusty skin
- Sudden bleeding
- Severe itching
- Partial pain
In most cases, surgical excision is recommended for therapy here. As a rule, this is also done very generously in order to completely remove all residues.
Dogs with squamous cell carcinoma usually develop a reddish bump under the skin, which can sometimes be painful. Large dog breeds of advanced age are particularly affected. In this case, you need to seek medical help.
Rarer causes
- Sebaceous adenoma
- Hemangioma
- Chondrosarcoma
- Skin tag
- Granuloma
- Breast cancer
- Osteosarcoma