What Causes Subcutaneous Swelling in Dogs? Causes and Symptoms of Sebaceous Glands, Tumors, and Infections

The Most Common Causes of Subcutaneous Swelling in Dogs

Subcutaneous lumps in dogs can have a wide range of causes, from simple, harmless sebaceous glands to serious tumors. Therefore, not every lump is considered the same. The most important characteristic of subcutaneous lumps is that they manifest differently depending on the dog's immune system, age, breed predispositions, and lifestyle.

One of the most common causes is lipoma , or fatty tissue. Lipomas are more likely to develop in aging dogs and are generally harmless. However, malignant fatty tissue tumors similar to lipomas, such as liposarcoma, can also occur, so each mass should be evaluated individually.

Another common cause is abscess formation. Through bite wounds, stinging objects, trauma, or disruption of skin integrity, bacteria can settle under the skin, causing infection and pus-filled swellings. These swellings can enlarge rapidly and are often painful.

Cysts can also form due to congenital textural abnormalities or blocked hair follicles. Some may remain unchanged for years, while others can grow rapidly.

Tumors are the most common cause of swelling. Mast cell tumors , soft tissue sarcomas, and other malignant tumors can develop as a mass under the skin. While these types of swellings may appear innocent in the early stages, they can become aggressive later on.

In short, subcutaneous lumps can be a symptom of a wide range of conditions. Therefore, every lump requires professional evaluation.

Symptoms and Early Warning Signs of Subcutaneous Swellings

The symptoms of subcutaneous lumps vary depending on the underlying cause. Some lumps are small, soft, and may remain stable for years, while others grow rapidly, cause pain, or affect the dog's overall condition. Therefore, owners should evaluate the lump not only by its size but also by its behavior.

The most common early symptom is a small swelling under the skin . This swelling is usually noticed while petting, combing, or bathing the dog. The hardness, mobility, warmth, and surface adhesion of the swelling are important clues.

Pain and tenderness are the most significant signs of swelling caused by infection or trauma. If the dog reacts to the swelling when touched, this raises the possibility of inflammation or a pus-filled abscess.

Rapid growth is a critical early warning sign, especially in malignant tumors. Any lump that grows significantly over a few weeks, changes shape, or develops redness on its surface requires prompt evaluation.

Symptoms such as color change , increased temperature , discharge , hair loss , the urge to scratch , limping, fatigue , and decreased appetite are also important. Multiple swellings in different parts of the body may indicate a systemic disease.

Any swelling noticed early should be monitored and checked regularly for growth or change.

Fatty Glands (Lipoma): Why Do They Form and How to Identify Them?

Lipomas are the most common type of subcutaneous swelling in dogs. They are more common in older, middle-aged, and overweight individuals. Lipomas are caused by the uncontrolled but benign proliferation of fat cells. Most lipomas are harmless and can remain the same size for years; however, some can grow and restrict a dog's movement.

How to recognize lipoma?

Lipomas typically:

• It has a soft consistency

• It can slide under the skin when gently pushed with fingers.

• It does not cause pain

• It grows slowly

• It can be seen throughout the body, but it occurs most frequently in the abdomen, chest and shoulder areas.

The most common malignant mass often confused with a lipoma is liposarcoma . Liposarcomas resemble lipomas but are more solid, can adhere to a surface, and tend to grow rapidly. Therefore, any lipoma-like mass requires professional evaluation.

Why does lipoma occur?

• Genetic predisposition

• Hormonal factors

• Having a high body fat percentage

• Middle-old age

• Metabolic slowdown

Is lipoma dangerous?

While most lipomas are harmless, deep lipomas or large lipomas that occur around joints can restrict a dog's movement. Very large lipomas may require surgery.

Cysts, Fluid-Filled Masses, and Encapsulated Swellings

Cysts are sacs filled with fluid, semi-fluid, or thick material that form under the skin. Most cysts are painless on their own; however, if fluid buildup within the capsule increases, the swelling can enlarge, rupture, or become infected.

Types of cysts:

• Sebaceous cyst: Occurs when hair follicles become blocked; it's filled with a thick, cheesy material. When it ruptures, it releases a foul-smelling discharge.

• Dermoid cyst: A congenital textural anomaly; may contain hair, oil and keratin.

• Fluid-filled capsules: May occur due to accumulation of blood or tissue fluid after trauma.

• Ganglion-like cysts: Rarely seen in joint areas.

How to distinguish cysts?

• They are generally round structures with clear boundaries.

• It can be medium hard

• It doesn't grow very fast

• It may feel like a slight ripple when pressed with a finger.

• Pain is mostly absent

• When it bursts, the risk of inflammation increases

Are cysts dangerous?

It is usually harmless, but:

• Ever-growing

• Becoming painful

• Reddening

• Leaky

• Recurrent cysts should be evaluated.

Infection-Related Swellings (Abscesses and Inflammation Foci)

Infections that develop under the skin in dogs are often referred to as abscesses , which are pus-filled swellings. These swellings usually develop rapidly and are characterized by significant pain. Abscess formation begins with bacteria penetrating the skin; this can occur as a result of bite wounds, sharp object punctures, nail scratches, traumatic injuries, or any other factor that disrupts skin integrity.

Typical features of infection-related swellings include:

• Significant growth in a short time

• Warming and redness of the area

• Pain and tenderness

• The dog licks or scratches the area

• Systemic symptoms such as fever, fatigue, and loss of appetite

• Softening of the center of the swelling (pus accumulation)

If left untreated, abscesses can rupture, stretching the skin surface, and discharge can occur. This discharge can be foul-smelling and yellow-green. Rupture does not mean healing; on the contrary, the area becomes an open wound, making it more susceptible to secondary infections.

Treatment usually includes:

• Professional opening and draining of the area

• Antibiotic treatment

• Local antiseptic applications

• It is necessary to address the root cause of the trauma.

Swellings caused by infection are usually a danger sign and are not expected to go away on their own.

Benign Tumors and Their Growth Patterns

A significant portion of subcutaneous lumps are benign tumors . These tumors can appear anywhere in the body and are often slow-growing. Benign tumors do not metastasize, meaning they do not spread to other parts of the body. However, they still require monitoring, as some can grow larger over time and cause mechanical discomfort.

Common types of benign tumors in dogs include:

• Lipoma: The most common benign mass originating from fatty tissue.

• Histiocytoma: A reddish, round, rapidly growing tumor seen in young dogs but usually regressing spontaneously.

• Fibroma: A firm, benign tumor arising from fibrous tissue.

• Papilloma: Viral-induced, cauliflower-shaped formations close to the skin surface.

Benign tumors usually:

• It grows slowly

• It does not cause pain

• Surrounded by clear boundaries

• Moves easily under the skin

However, some benign tumors, such as lipoma, can put pressure on deep tissues, causing limited movement, difficulty walking, or local pain.

Although benign, benign tumors require regular monitoring. If new symptoms such as rapid growth, discoloration, ulceration, or pain appear, the tumor may be considered malignant.

Malignant Tumors (Cancer) and Danger Signs

The most serious category of subcutaneous lumps are malignant tumors . These tumors can grow rapidly, damage surrounding tissues, and metastasize. If not detected early, they can be life-threatening.

The most common malignant subcutaneous tumors in dogs:

• Mast Cell Tumor (MCT)

• Liposarcoma

• Soft Tissue Sarcoma

• Fibrosarcoma

• Hemangiosarcoma

The danger signs of these malignant tumors are quite obvious:

• Rapidly growing swelling

• Rough or irregular surface structure

• A mass that is attached to the skin and does not move

• Change in color (redness, bruising)

• Ulceration (opening of the skin)

• Discharge or foul odor

• The dog feels pain when the swelling is touched

• Significant increase in size in a short time

• Systemic findings such as weakness, loss of appetite, and fatigue

If any of these symptoms are present, the possibility of a malignant tumor should be seriously considered. Early biopsy and imaging significantly increase the chance of cure. Treatment may include surgery, chemotherapy, radiation therapy, or comprehensive monitoring.

Swellings Developing After Trauma, Impact and Injuries

A significant portion of subcutaneous swelling in dogs is caused by trauma . Localized edema or a hematoma (blood accumulation) may occur under the skin as a result of hitting a hard object during play, falling, a play fight with another dog, or being stabbed by a sharp object.

Characteristics of post-traumatic swelling:

• It usually occurs suddenly

• The area may feel warm, tender, or painful when touched.

• Bruising, redness or fluid accumulation under the skin may occur.

• The dog may lick the area, increasing the irritation.

• Some hematomas may be hard, while others may be soft, giving the feeling of fluid fluctuation.

Swelling caused by trauma is usually harmless, but in some cases, serious internal tissue damage can occur. Ear hematomas, in particular, cause the ear flap to swell like a bubble due to internal bleeding, which may require surgery.

Symptoms to be considered during post-traumatic observation:

• The swelling grows over several days

• Increased pain

• Gait disturbance

• Bleeding, discharge, or sores

• Change in the dog's normal behavior

Veterinary evaluation is essential when these symptoms are present. Post-traumatic swelling can sometimes be simple edema, or it can be a sign of deep tissue damage.

Allergic Reactions, Insect Bites, and Sudden Swellings in Dogs

Allergic reactions and insect bites are among the most common causes of sudden swelling under the skin in dogs. In some dogs, the immune system can overreact to even a harmless insect bite. Bites from bees, wasps, spiders, flies, ants, ticks, and fleas, as well as even contact with certain plants, can cause significant swelling in a short time.

Typical features of allergic swellings are as follows:

• Swelling occurs very quickly

• Redness of the area

• Itching or burning sensation

• The dog's tendency to constantly lick the area

• Swelling usually occurs on the face, lips, around the eyes or on the paws.

• Sometimes blisters or hives-like rash appear all over the body

The most critical symptoms of allergic reactions are sudden facial swelling and difficulty breathing . Anaphylaxis is a risk, especially in cases of bee stings or severe sensitization. This condition can be life-threatening.

Bugs caused by insect bites usually enlarge within a few hours and then slowly begin to shrink. However, if an infection is present, the swelling can progress and become painful.

Common triggers in the home environment:

• Mosquito bites

• flea allergy

• Plant pollen

• Chemical substances (bleach, detergent residues)

• Dust mites

Allergic swellings can be dangerous, so professional help should be sought without delay, especially for rapidly growing swellings in the facial area.

In Which Situations Do Subcutaneous Swellings Require Emergency Intervention?

Not every subcutaneous lump is an emergency, but certain symptoms indicate the severity of your dog's condition. In these cases, veterinarian attention should be sought immediately.

Emergency warning signs include:

• Rapidly growing swelling (significant increase within hours)

• Pain, tenderness and increased temperature

• Swelling in the face, lips or throat area

• Difficulty breathing, wheezing or coughing

• The dog becomes lethargic, wants to lie down, tremors

• Bruising, discoloration, or bleeding from the swelling

• Open wounds, inflammation, or foul-smelling discharge

• The dog does not let the swelling touch it and becomes aggressive.

• A single swelling turns into multiple swellings in a short time

• Your dog is vomiting, has diarrhea, or has a loss of appetite

These symptoms usually include:

• Mast cell tumors

• severe allergic reaction

• Abscess formation

• Traumatic tissue damage

• Bleeding foci

• It indicates situations that require urgent evaluation, such as systemic spread of infection.

Dog owners should not take the "let me watch for a while" approach, as some malignant tumors or allergic reactions can become critical within hours.

Diagnostic Process: Examination, Ultrasound, Biopsy and Other Methods

A correct diagnosis of subcutaneous lumps cannot be made solely by physical examination. A combination of diagnostic methods is often used to definitively determine the mass's structure, origin, and whether it is benign or malignant.

1. Physical Examination

Veterinary audience:

• Dimension

• Hardness

• Mobility

• Adhesion to the surface

• It evaluates according to criteria such as temperature and pain status.

2. Fine Needle Aspiration Biopsy (FNAB)

A thin needle is inserted into the swelling and a cell sample is taken. This method:

• Lipomas

• Tumor types

• Infection foci

• It is the most effective diagnostic test to quickly differentiate the contents of cystic structures.

3. Ultrasound

It determines whether the underlying tissue is liquid or solid. It also indicates the depth of the swelling, the presence of a capsule, and tissue relationships.

4. X-ray

It is used to find out whether the mass has metastasized to the bone or chest cavity.

5. Excisional Biopsy

The entire mass is surgically removed and sent for pathology. This is the gold standard, especially for mast cell tumors and sarcomas.

6. Blood Tests

It is valuable if systemic infection, inflammation or cancer is suspected.

An accurate diagnosis is the foundation of a treatment plan. Only through this process can we determine whether the swelling is innocent or not.

Treatment Options: Medication, Surgery, and Follow-up Protocols

The treatment approach is determined entirely by the cause of the swelling, the rate of growth, the dog's age and systemic condition.

1. Lipoma Treatment

Most lipomas do not require treatment. However:

• If it grows too much

• If it affects walking/sitting movements

• If it puts pressure on deep tissues, surgical removal is preferred.

2. Cyst Treatment

Cysts are usually monitored. Ruptured cysts can become infected, in which case:

• Antibiotic

• Antiseptic care

• If necessary, surgical removal is performed.

3. Infection / Abscess Treatment

• Draining the abscess

• Antibiotic treatment

• Local dressing

• The underlying trauma needs to be treated.

4. Benign Tumor Treatment

Small, stable tumors can only be monitored. Those that are growing are surgically removed.

5. Malignant Tumor Treatment

Treatment must be aggressive and multifaceted:

• Extensive surgery

• Chemotherapy protocols

• Radiotherapy when necessary

• Close monitoring

6. Treatment of Allergy-Related Swelling

In case of allergy:

• Antihistamine

• Corticosteroids

• Cold compress

• Allergen control is applied.

7. Treatment of Trauma-Related Swelling

• Ice application

• Painkillers

• If necessary, hematoma drainage is applied.

Regular check-ups, re-examinations, and growth monitoring play a critical role in the success of treatment.

Safe Observations and Supportive Methods That Can Be Done at Home

When you notice a subcutaneous lump in your dog, some safe observations you can make at home can help understand the swelling's behavior and prepare for a veterinary visit. However, these methods are not a substitute for treatment; they simply make it easier to assess the situation.

First, the size , firmness , adherence to the surface , and mobility of the swelling should be carefully assessed. Gentle pressure with the fingertips can help better palpate the mass. Soft, slippery, and easily movable masses under the skin are generally suggestive of benign conditions such as lipomas. Firm, irregular-surfaced, and immobile masses should be monitored more carefully.

The rate of swelling growth is one of the most critical monitoring parameters. A simple method can be used for this:

• The area around the swelling can be lightly marked with a pencil.

• Size changes can be monitored by taking photos weekly.

If there are signs such as increased heat , redness , pain , discharge , foul odor , or the dog licking the area, the suspicion of infection increases and home monitoring will not be sufficient.

Supportive measures include cold compresses (for trauma-related swelling), keeping the area clean, avoiding hot towels, and preventing the dog from touching the swelling excessively. However, under no circumstances should you attempt to squeeze, pop, or needle the mass; these attempts significantly increase the risk of infection.

Using natural remedies or random creams at home is not recommended. Applying products without knowing the nature of the swelling can both delay diagnosis and worsen the condition. Home observation is only a preliminary step before professional evaluation.

Care and Control Recommendations to Prevent Recurrence of Swelling

Even if some subcutaneous lumps are treated, they tend to recur. Therefore, long-term care and regular checkups can help detect new lumps early and reduce risk factors.

First and foremost, it's important for your dog to be within their ideal weight range . Increased fat tissue can trigger lipoma formation, so proper nutrition and daily exercise can reduce the risk of recurrence.

Regular coat and skin care helps maintain healthy skin. Blocked hair follicles can increase the risk of cysts and abscesses. Therefore, regular brushing, proper drying after bathing, and quality care products are crucial.

The cleanliness of your dog's living space is also an important factor in preventing recurrence. Dirty floors, bacteria, and parasites can trigger infection. Furthermore, regular antiparasitic treatments should be maintained to protect against external parasites.

Veterinary checkups should be performed not only during periods of illness, but also at least once a year, with a full-body examination. These checkups are especially crucial, as the incidence of subcutaneous lumps increases in aging dogs.

More frequent checkups are recommended for breeds prone to subcutaneous lumps (such as Boxers, Labradors, Golden Retrievers, and Mastiffs). Masses detected early are easier and more successful to treat.

Finally, preventing traumatic injuries and keeping the dog moving in safe areas also prevents hematomas and swelling due to trauma.

FAQ - Subcutaneous Swellings in Dogs

What is the most common cause of swelling under the skin in dogs?

The most common cause of subcutaneous swellings in dogs is fatty glands called lipomas. They are common in older, middle-aged, and overweight dogs. However, this doesn't mean all swellings are innocent. Cysts, infections, abscesses, benign tumors, and malignant tumors can also occur under the skin in similar ways.

My dog has a soft mass under his skin, is it dangerous?

Soft, movable, and painless swellings are often benign, such as lipomas; however, this is not a guarantee. Some malignant tumors can also start out soft and harden over time. The growth rate and shape of the swelling, as well as changes in the dog's behavior, provide important clues.

What does it mean if there is a hard and immovable lump under the skin?

Swellings that are firm, have irregular surfaces, and feel adherent to the skin surface should be evaluated more carefully. These structures are particularly characteristic of malignant tumors. Mast cell tumors, sarcomas, and liposarcomas can have such a firm structure. In these cases, early biopsy is crucial.

What causes sudden swelling in dogs?

Sudden swelling often occurs due to allergic reactions, insect stings, bee or wasp contact, trauma, or rapidly developing abscesses. Rapid growth of the swelling, redness, or itching in the dog increase the likelihood of an insect bite or allergy. Sudden facial swelling requires immediate attention.

How to distinguish between lipoma and malignant tumor?

Lipomas are generally soft, slippery, and painless. They grow slowly and are not attached to surrounding tissues. In contrast, malignant tumors are generally harder, have irregular surfaces, and grow rapidly. However, definitive diagnosis is only possible with a fine-needle aspiration biopsy or pathological examination.

How to recognize an abscess in dogs?

An abscess is a pus-filled, infection-filled area that is usually painful. The swelling is warm, red, tender, and rapidly enlarging. The dog will constantly lick the area. In advanced stages, the abscess may rupture spontaneously, producing a foul-smelling discharge. This requires immediate veterinary attention.

Are cysts dangerous in dogs?

Cysts are usually harmless, but they can cause discomfort or become infected when they grow. The risk of infection increases, especially when sebaceous cysts rupture. If a cyst grows rapidly, causes pain, or changes color, it should be evaluated.

My dog's lump hurts when I touch it. Why?

Pain is most common in swellings caused by infection, abscess, trauma, or inflammation. In infected swellings, the tissue becomes tender to the touch due to stretching. Bleeding sites or deep hematomas may also be sensitive to the touch.

How to recognize mast cell tumors in dogs?

Mast cell tumors vary greatly in appearance. They may appear as a small, innocuous bump, but they typically exhibit rapid growth, surface redness, an urge to scratch, ulceration (opening of the skin), and discoloration.

My dog's lump has gotten bigger over the past few weeks, is this dangerous?

Yes. Rapid growth is one of the most important warning signs of malignant tumors. Benign tumors like lipomas typically grow over months, while any mass that grows significantly within weeks requires urgent evaluation.

Is post-traumatic swelling normal in dogs?

Swelling or hematomas may occur in areas exposed to impact during play. These swellings should begin to diminish within a few days. However, if they enlarge, become bruised, or if the dog avoids the pain, a professional evaluation is necessary.

What does it mean if the swelling is hot?

A localized temperature increase is often a sign of inflammation or infection. A temperature increase is expected in abscesses, abscessed wounds, and trauma-related hematomas. Monitoring is important in these cases, as the risk of infection increases.

The lump on my dog has burst, what should I do?

The rupture of the swelling doesn't mean it's healed. On the contrary, the open wound is more susceptible to infection. It's essential to clean the area with sterile water and seek professional treatment. Self-squeezing is very dangerous.

Why is facial swelling dangerous in dogs?

Sudden facial swelling is often caused by allergies or insect bites. This condition can progress rapidly and affect the respiratory tract. Swelling of the lips, eyelids, or throat requires immediate attention.

What does it indicate if a dog has multiple swellings?

Multiple lumps can be seen in benign tumors such as lipomas. However, some types of cancer (mast cell tumors, lymphomas) or systemic diseases can also present with multiple lumps. In these cases, a detailed examination is necessary.

Can swelling disappear on its own?

Some small swellings caused by allergies or trauma may shrink on their own. However, cysts, lipomas, tumors, and most infectious swellings do not disappear on their own. Even swelling that resolves on its own can recur.

Can I reduce swelling with natural methods at home?

No. Applying natural mixtures, oils, or heating products without knowing the tumor site can worsen the condition. Some tumors do not tolerate manipulation and can accelerate growth. The only safe home remedies are cold compresses and cleansing.

How can I tell at home whether the lump is a lipoma?

It's impossible to make a definitive diagnosis at home. Lipomas are usually soft and move freely; however, malignant tumors such as liposarcoma can begin with similar symptoms. A definitive diagnosis is made with a fine-needle aspiration biopsy.

Are subcutaneous lumps in dogs more common in older dogs?

Yes. The incidence of swelling increases with age due to changes in the immune system, increased fatty tissue, decreased skin elasticity, and a slower cell turnover rate. In older dogs, any new swelling should be carefully evaluated.

How do I know if a lump on my dog is cancerous?

It's impossible to diagnose a tumor based on a single external symptom. However, rapid growth, hardness, irregular surface, adhesion to the skin, discoloration, and ulceration are all suggestive of malignant tumors. However, definitive diagnosis is only possible with a biopsy.

Why do infection-related swellings in dogs smell bad?

Bacteria multiply rapidly in infected swellings, and the dissolved tissue produces a foul-smelling discharge. This is often seen in ruptured abscesses and requires immediate treatment.

What happens if subcutaneous lumps in dogs are not treated?

Untreated swelling:

• It can grow

• It may become infected

• It can pierce the skin surface and cause discharge.

• If it is a tumor, it can progress and metastasize.

• May restrict the dog's movement

• May cause pain and serious reduction in quality of life

Therefore, every swelling should be followed seriously.

My dog's swelling is small but it hasn't gone away for a long time, what should I do?

Small, long-lasting lumps are generally benign; however, it's not safe to assume they're completely harmless. Regular measurements, photo monitoring, and veterinary follow-up are necessary. A definitive diagnosis cannot be made without a biopsy.

Can subcutaneous swellings recur?

Yes. Lipomas can recur, cysts can refill, and abscesses can recur in the same area. Furthermore, some tumors can regrow after removal. Therefore, regular checkups are important.

Is it possible to completely prevent subcutaneous swelling in dogs?

It is not possible to prevent it completely; however, regular care, maintaining ideal weight, healthy nutrition, preventing trauma and annual veterinary check-ups greatly reduce the risks.

Sources

• Cat Fanciers' Association (CFA)

• The International Cat Association (TICA)

• American Veterinary Medical Association (AVMA)

• Mersin Vetlife Veterinary Clinic – Open on Map: https://share.google/XPP6L1V6c1EnGP3Oc