Swollen Lymph Nodes in Dogs: Symptoms, Causes & Treatment Tips

Early detection and vet-guided care can make all the difference for your furry friend.

By Srija Burman

Created on Aug 29, 2025

Early detection and vet-guided care can make all the difference for your furry friend.

Swollen Lymph Nodes in Dogs: Causes, Symptoms, Diagnosis, and Treatment

Lymph nodes are a critical component of your dog’s immune system, helping to trap and destroy bacteria, viruses, and other harmful substances. Swelling of these nodes, known as lymphadenopathy, often signals that the body is fighting an infection or other immune challenge. This article provides a thorough overview of swollen lymph nodes in dogs, outlining potential causes, related symptoms, diagnostic procedures, treatment options, and important care tips for pet owners.

What Are Lymph Nodes?

Lymph nodes are small, bean-shaped glands scattered throughout a dog’s bodyâprimarily found near major joints and internal organs. They contain white blood cells that defend against disease. The lymphatic system, which includes these nodes, is vital for immune surveillance and plays a role in fluid balance and filtering out harmful substances.

Main Functions of Lymph Nodes in Dogs

Filtering lymph fluid to trap bacteria, viruses, and foreign particles
Producing and housing lymphocytes (white blood cells)
Coordinating the immune response to infection or other diseases

Common Lymph Node Locations in Dogs

Submandibular (beneath the jaw/neck area)
Prescapular (front of the shoulders)
Axillary (armpit area)
Inguinal (groin region)
Popliteal (behind the knees)

What Are Swollen Lymph Nodes (Lymphadenopathy)?

Swollen lymph nodes, or lymphadenopathy, refer to the enlargement of one or more lymph nodes in response to abnormal stimuliâmost often due to inflammation, infection, or cancer. Typically, healthy lymph nodes are not easily noticeable. Swelling often becomes the first obvious sign that something may be wrong and warrants medical attention.

Why Do Lymph Nodes Swell?

Increase in white blood cells responding to infection
Accumulation of inflammatory or cancerous cells
Direct infection, immune-mediated disease, or infiltration by malignant cells

Causes of Swollen Lymph Nodes in Dogs

There are many potential reasons why a dog may develop swollen lymph nodes, and the underlying cause significantly impacts treatment and prognosis.

Common Causes

Infections: Bacterial, viral, fungal, or parasitic infections (including abscesses, skin, dental, respiratory, or systemic infections)
Cancer: Especially lymphoma, a malignancy of the lymphatic system; metastasis from other cancer types is also possible
Immune-mediated disease: Disorders where the immune system attacks the bodyâs own tissues, such as lupus or autoimmune hemolytic anemia
Localized trauma: Physical injury to or near a lymph node may result in temporary swelling
Other causes: Allergic responses, certain medications, or idiopathic (unknown) reasons

Breakdown of Common Infectious Causes:

Bacterial: Abscesses, skin infections, dental disease
Viral: Distemper, parvovirus, adenovirus
Fungal: Histoplasmosis, blastomycosis
Parasitic: Heartworm, tick-borne diseases (e.g., Lyme disease)

What Do Swollen Lymph Nodes Look and Feel Like?

Swollen lymph nodes may become visibly enlarged or palpable (felt as a lump under the skin). They are usually firm or rubbery to the touch and may move easily beneath the skin, though in some cases (especially if malignant), they can be fixed and immobile.

Submandibular nodes: A lump under the jaw, sometimes confused with a swelling from a dental problem
Prescapular and popliteal nodes: Palpable as firm swellings above the shoulder or behind the knee, respectively
Inguinal and axillary nodes: May cause swelling in groin or underarms, occasionally making movement uncomfortable for the dog

In severe cases, nodes can grow dramatically, stretching the skin or becoming visible to the naked eye. In cases of cancer, the skin overlying the node may ulcerate or become discolored.

Symptoms Associated with Swollen Lymph Nodes

While some dogs may exhibit no other symptoms aside from the swelling, others may experience a wide range of clinical signs depending on the underlying cause, the extent of lymph node involvement, and whether the swelling is localized or generalized.

Possible Clinical Signs

Lethargy or listlessness
Fever
Pain or discomfort, especially if nodes are large
Loss of appetite
Weight loss
Visible swelling or lumps
Lameness or difficulty moving, if swelling is near a limb joint
Respiratory symptoms or coughing, if nodes in the chest are involved
Difficulty swallowing, if submandibular nodes are greatly enlarged

How Veterinarians Diagnose Swollen Lymph Nodes

Accurate diagnosis is essential for determining the cause and directing effective treatment. Since swollen lymph nodes can be caused by anything from a mild infection to life-threatening cancer, prompt veterinary evaluation is always recommended.

Diagnostic Steps

Medical History & Physical Exam: Gathering information about your dogâs symptoms and performing a thorough examination, including checking all the palpable lymph nodes
Fine Needle Aspiration (FNA): Inserting a thin needle into the swollen lymph node to withdraw a small sample of cells for examination under a microscope; this helps differentiate between reactive/infectious and malignant causes
Biopsy: Surgically removing a piece or entirety of the node for detailed analysis, often used when FNA is inconclusive or lymphoma is suspected
Blood Tests: Checking for evidence of systemic infection, immune-mediated disorders, or blood cell abnormalities
Imaging (X-rays, Ultrasound, CT scan): Assessing internal lymph nodes and ruling out metastasis or underlying disease
Additional Tests: Such as urinalysis, specific infectious disease panels, or flow cytometry for cancer analysis

Treatment of Swollen Lymph Nodes in Dogs

Treatment varies depending on the underlying cause. After diagnosis, a veterinarian will select the most appropriate therapy:

Common Treatments

Antibiotics or Antifungals: For bacterial/fungal infections causing lymphadenopathy
Parasiticides: For parasitic infestations (e.g., heartworm or tick-borne disease)
Chemotherapy: For cancer, particularly lymphoma
Immunosuppressive or Anti-inflammatory drugs: For immune-mediated conditions
Pain management and supportive care: May include NSAIDs, fluids, appetite stimulants, or sedatives as appropriate

Prognosis

The prognosis depends on the underlying cause, how early it is detected, and how well the dog responds to treatment. Infections caught early and treated appropriately carry a better outlook. Immune-mediated or cancerous disease may involve longer, more complex treatment protocols.

Home Care and Management

Always follow your veterinarian’s treatment plan and instructions precisely
Never attempt to treat swollen lymph nodes at home without veterinary advice
Monitor your dogâs condition, appetite, energy levels, and the size/appearance of the swelling
Keep scheduled recheck appointments; early follow-up can make a crucial difference, especially if the condition worsens or fails to improve
Provide a comfortable, stress-free environment and easy access to food and water

Can Swollen Lymph Nodes in Dogs Be Prevented?

Because there are many causes, not all cases of lymphadenopathy can be prevented. However, general wellness practices can significantly reduce your dog’s risk of infectious or immune-mediated diseases:

Maintain up-to-date vaccinations and routine parasite prevention
Practice good dental hygiene
Keep your dog away from known toxins or infectious environments
Schedule regular veterinary checkups for early detection

When to Call the Vet

Swollen lymph nodes are always a medical concern, even if your dog otherwise seems well. Contact your veterinarian promptly if you notice:

New, persistent, or rapidly enlarging lumps or swellings
Swelling associated with pain, fever, lethargy, or appetite loss
Changes in your dogâs breathing, mobility, or swallowing
No improvement or worsening of symptoms after starting treatment

Frequently Asked Questions (FAQs)

Q: Are swollen lymph nodes in dogs always a sign of cancer?

A: No. Although cancer (especially lymphoma) is a major cause, infections, immune-mediated diseases, or localized inflammation are also common reasons for lymph node swelling.

Q: How can I tell if my dog’s lymph nodes are swollen?

A: You may feel or see non-painful swellings in the areas under the jaw, in front of the shoulders, behind the knees, or in the groin. In some cases, only your veterinarian will be able to detect the enlargement during a physical exam.

Q: Is lymphadenopathy in dogs painful?

A: Swollen nodes themselves are not usually painful, unless the swelling is substantial or due to infection/inflammation. Dogs may, however, be uncomfortable or have difficulty moving if a large node compresses nearby tissues.

Q: Can I treat my dog’s swollen lymph nodes at home?

A: No. Determining the cause of swollen lymph nodes requires veterinary evaluation. Proper diagnosis and specific therapy are essential, and attempting home remedies can delay careâsometimes with serious consequences for your pet’s health.

Q: What is the prognosis for dogs with swollen lymph nodes?

A: This depends entirely on the underlying problem. Many infections resolve quickly with treatment, while lymph node cancer may require intensive care and has a variable outlook depending on staging and response to therapy.

Summary Table: At-a-Glance Reference

Aspect	Description
Normal Lymph Node Size	Usually not visible or easily felt
Common Causes of Enlargement	Infections, cancer, immune-mediated disease, trauma
Common Locations for Swelling	Submandibular, prescapular, axillary, inguinal, popliteal
Key Symptoms	Swelling/lump, lethargy, fever, appetite loss, weight loss
Diagnosis	Physical exam, FNA, biopsy, bloodwork, imaging
Main Treatments	Cause-specific: antibiotics, immunosuppressants, chemotherapy

Conclusion

Swollen lymph nodes in dogs are a common clinical sign of underlying disease. Early veterinary evaluation is vital for accurate diagnosis and effective treatment. By knowing what to look for and acting quickly, pet owners can give their dogs the best chance at a full recovery, regardless of the cause of lymphadenopathy. Regular health checkups and preventive care are the best tools for keeping your companion healthy and detecting potential issues before they become serious.

References

Author

Srija Burman

Srija holds an MA in English Literature from the University of Calcutta and a PG diploma in Editing and Publishing from Jadavpur University. Her interest in writing and editing ranges across niches, including academics, sports, and human psychology.

Read full bio of Srija Burman