When dogs suddenly have a lump under their skin, it is often a sac, an abscess or a lipoma. In some cases, it can also be caused by hives and various tumors, which should be treated immediately.
For laypeople, these knots are usually difficult to distinguish from one another. For this reason, I recommend that you always consult a veterinarian as a precaution in the event of such problems.
Below you will learn about the 9 most common causes and how you can recognize them. You will also find out which breeds are primarily affected by this.
Are you worried or unsure? Then click here to start a live chat with a veterinarian.
#1 Grit bag
A sac is a cyst that occurs due to a blocked sebaceous gland. Doctors also refer to this as an “atheroma”.
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 in heavily 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 [1]
As dangerous and frightening as this knot may look, it is usually harmless. It only becomes a problem if it becomes inflamed due to bacteria.
From a certain size, the groats bag can also restrict the dog's movements. In such a case, it is usually removed surgically by the vet. [2]
If a sebaceous sac forms in dogs due to a blocked sebaceous gland, this can usually be recognized by a lump under the skin. This lump is usually painless, relatively elastic, grows slowly and usually occurs in very hairy areas.
#2 Abscess
If pus accumulates in the tissue in an encapsulated form, then doctors speak of an “abscess”. It is also colloquially known as a “sulcer”.
In most cases it is caused by a bacterial infection. This is especially true after bite wounds from other animals, which allowed pests to enter.
What is noticeable here is that the lump under the skin develops very quickly and causes pain. The most common signs include:
- Redness around the area
- Mild fever
- Dog keeps licking the area
- Touch sensitivity
- Slight bleeding around the area
- Loss of appetite [3]
For treatment, the lump is usually squeezed out by the veterinarian and cleaned or removed surgically. The wound is also cleaned and antibiotics are prescribed.
Depending on the cause and severity, further measures may also be necessary. However, such an ulcer does not have any long-term consequences. [4]
When a bacterial infection occurs in dogs and pus accumulates under the skin, it is usually recognizable as a reddish lump. Such abscesses are usually harmless but painful. Affected dogs also often get a fever.
#3 Lipoma
If a benign skin growth occurs in the fatty tissue, doctors speak of a “lipoma”. This is one of the most common types of tumors.
Basically, this fatty tumor can occur anywhere. The cause of this is still unclear. What is noticeable, however, is that the tumor can be easily moved and is soft.
However, it may also feel hard if it spreads under a muscle. Other typical symptoms of this are:
- Sometimes several lumps under the skin
- No pain or sensitivity to touch
- No redness or swelling [5]
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. Here you should seek medical attention. [6]
A benign growth of fatty tissue can appear as a lump under the skin in dogs. Typically, lipomas are relatively soft, painless and occur more often in overweight dogs. Sometimes there are even several of them.
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#4 Mast cell tumor
Mast cells are the body's own cells that help defend against pathogens and allergens. If a tumor forms there, it is usually malignant. [7]
Unfortunately, mast cell tumors in dogs are also one of the most common skin tumors. The cause of this is still unclear. However, the following breeds are increasingly affected:
- German boxer
- Bernese Mountain Dog
- Boston terriers
- Labrador retrievers
- Bull Terrier
- beagle
- schnauzer [8]
As a rule, a mast cell tumor appears as a rounded lump under the skin and has a diameter of between 1-3 cm. Other typical signs are:
- Slight redness
- Changing size
- Hair loss at the site
- Surrounding swelling [9]
Treatment depends on the degree of severity. The tumor is usually removed via surgery. Chemotherapy and radiation therapy can also be carried out after spreading.
Dogs with a mast cell tumor usually develop a reddish lump under the skin that is between 1-3 cm in size. What is noticeable here is that the knot is rounded and can vary in size. The earlier it is diagnosed, the better the chances of recovery.
#5 Histiocytoma
Histiocytes are cells that are responsible for immune defense. However, if these multiply abnormally, doctors also speak of a “histiocytoma”.
It is a benign tumor of the skin. The cause of this is still unclear, but young dogs and the following breeds are said to be more likely to be affected:
- Bull Terrier
- German boxer
- Boston terriers
- American Pit Bull Terrier
- Labrador retrievers
- Shar Pei [10]
In most cases, a histiocytoma can be recognized by a red lump under or on the skin. Other typical symptoms are:
- Hairless bun
- Under 2.5cm diameter
- Bright red bubble
- Mostly on the head or ears
- Sudden appearance [11]
Typically, this tumor resolves 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 goes away on its own within a few weeks.
#6 Fibrosarcoma
A fibrosarcoma is a malignant tumor consisting of connective tissue cells. In most cases, it develops on the dog's legs or torso.
It also sometimes occurs in the nasal cavity and mouth. The underlying cause is still unknown. However, the following breeds are said to be affected more frequently:
- Irish wolfhound
- Golden retrievers
- Doberman
- Epagneul Breton
- Gordon Setter [12]
But other large breeds of older age are also said to be more common here. To a trained eye it can usually be recognized by the following features:
- Tight knot
- Lumps under the skin
- Slow growth
- May open and bleed
- Difficulty getting up
- Social distancing
- Sometimes several lumps
- Loss of appetite [13]
For treatment, the tumor is usually removed via surgery. Depending on the location and characteristics, this is often only possible to a limited extent. In such cases, radiation therapy can help.
If a lump forms under the skin in the mouth or on the legs of large breeds at an advanced age, it is often a fibrosarcoma. This malignant tumor usually grows very slowly and also affects the dog's behavior.
#7 Black skin cancer
Unfortunately, black skin cancer is one of the most common skin diseases in dogs. Doctors also refer to this as a “melanoma”.
This most commonly occurs in the mouth 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 possible [14]
Unfortunately, this type of tumor is very aggressive and spreads quickly. It is therefore not uncommon for the lump under the skin to quickly increase in size.
The earlier the tumor is diagnosed, the better the chances of treatment and cure. If you suspect this, you should consult the vet immediately. [15]
Depending on the location and severity, black skin cancer in dogs 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 suddenly appears and sometimes itches.
#8 Hives
Hives is a non-contagious skin disease that is usually triggered by an allergic reaction. Other typical causes are:
- Insect bites
- Toxic plants
- Vaccinations
- Chemicals
- Allergens in food
- Insecticides [16]
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 in the face
- Dog drools profusely
- Usually 1-3 cm tall
- Partial redness [17]
Since allergies are usually responsible for this, antihistamines are increasingly being used for treatment. An allergy test is also useful for prevention.
Although these types of knots are annoying, they are usually nothing to worry about. They can only be dangerous if they make it difficult for the dog to breathe.
If dogs get several round lumps under their skin, it is often hives. It is usually triggered by allergens. It is also typical that there is severe itching and sometimes redness.
#9 Squamous cell carcinoma
Squamous cell carcinoma is a malignant tumor of the skin and mucous membranes. Basically it can occur anywhere. The following breeds are more commonly affected:
- Labrador retrievers
- Basset Hound
- Pekingese
- German boxer
- Norwegian Elkhound
- Golden retrievers
- poodle [18]
Older dogs over the age of 6 are usually affected. Large four-legged friends with short fur and dark skin who are in the sun a lot are more likely to suffer from this.
At first, this lump under the skin often looks like a wart, but then becomes progressively redder. Other typical features are:
- Inflammation possible
- Severe redness
- Crusty skin
- Sudden bleeding
- Severe itching
- Partial pain [19]
In most…