Swollen Lymph Nodes in Dogs: Common Causes and Treatment

Lymphadenopathy refers to swollen lymph nodes, which are found in different parts of a dog’s body. Swollen lymph nodes in dogs can happen for several reasons, ranging from mild to severe health concerns.

Taking your pet to the veterinarian is the best way to get a diagnosis and figure out next steps if you think your dog’s lymph nodes are swollen.

What Are Swollen Lymph Nodes in Dogs?

Lymph nodes are small, firm structures that are just underneath a dog’s skin. They are made up of lymphocytes, a type of white blood cell that helps fight infections.

Lymph nodes can become enlarged because of inflammation or various diseases, including cancer or infections.

It’s typically hard for a pet parent to find these tiny lymph nodes when they are of normal size.

However, as lymph nodes become swollen, pet parents may feel a noticeable bulge in the skin when playing with or petting their dogs.

Swollen lymph nodes in dogs can be found underneath the chin, in front of the shoulders, in the groin, or behind the knees. One or many lymph nodes in the body can be enlarged, depending on what is causing them to swell.

When dogs have swollen lymph nodes, they may show no other symptoms or they may be noticeably ill, depending on the underlying cause.

Swollen lymph nodes can be painful or cause discomfort if they have grown to be very large.

If you think one or more of your dog’s lymph nodes has become enlarged, it is best to schedule a veterinary appointment to get the right diagnosis.

Causes of Swollen Lymph Nodes in Dogs

Swollen in lymph nodes in dogs can occur for a variety of reasons, including:

• Cancer: Middle-aged and older dogs are more likely to develop cancer, but in rare instances, young dogs may be affected. Cancer can cause lymphadenopathy either through metastasis (spreading from other parts of the body) or by primary disease (it starts in the lymphatic system). Lymphoma is an example of a cancer that causes swollen lymph nodes.

• Infections: Bacteria, viruses, and fungi can cause infection in a dog and lead to swollen lymph nodes. Blastomycosis is an example of a fungal infection that may lead to lymphadenopathy.

• Tick-borne disease: Ticks can spread various illness to dogs that may cause swollen lymph nodes. Examples include Rocky Mountain spotted fever and Lyme disease.

• Autoimmune disease: When dogs have an overactive immune system, lymph nodes can become enlarged. An example of this type of disease is rheumatoid arthritis.

• Allergies: Dogs can have allergic reactions to environmental factors, such as pollen or grass, or to their diet. Allergies can cause inflammation within the body, which causes lymph nodes to swell.

• Parasites: If a dog is infected with a parasite, such as fleas, his lymph nodes can become swollen. This is especially true for chronic or severe infections.

• Dental disease: Dogs with severe dental disease often have enlarged lymph nodes underneath their chins. This can be the result of gum infections or tooth root abscesses.

• Abscess: If a dog has trauma or injury, bacteria can enter the skin wound and lead to swelling within nearby lymph nodes.

Are Swollen Lymph Nodes in Dogs an Emergency?

Swollen lymph nodes by themselves are not considered a medical emergency; however, many of the symptoms that can happen with lymphadenopathy are.

For example, dogs with swollen lymph nodes due to an underlying infection may also have reduced appetite, dehydration, and pale gums. These symptoms should be addressed right away by a veterinarian.

If you notice swollen lymph nodes in your dog, call a veterinarian to discuss your pet’s behaviors and decide on the next steps.

When To Call Your Vet

Pet parents should call their vet for guidance if they notice any type of firm swelling when petting their dog. The veterinarian will most likely ask to see the pet for an exam so that she can make an accurate diagnosis. 

If a dog has swollen lymph nodes and is extremely lethargic (no energy), has pale gums, or is vomiting, he should be brought to an emergency veterinarian immediately for diagnosis and treatment.

How Veterinarians Diagnose Swollen Lymph Nodes in Dogs

To diagnose the cause of swollen lymph nodes in dogs, a veterinarian will perform a physical exam.

If a veterinarian finds a swollen lymph node, he will do a test called a fine needle aspirate (FNA).

During this test, the veterinarian gently puts a needle into the lymph node to collect a sample of cells. This sample is put on a glass slide, stained, and viewed under a microscope to determine if there are any abnormalities. If needed, a vet will send this sample to a pathologist for a second opinion.

This test is helpful for finding infections, inflammation, or cancer.

Blood work and urinalysis can be done to check the dog’s overall health and look for signs of infection, inflammation, or other disease.

More testing, such as special lab tests or imaging, may be recommended by the veterinarian if needed.

Treatment of Swollen Lymph Nodes in Dogs

Swollen lymph nodes in dogs are treated depending on the underlying cause.

Possible treatment options include:

• Corticosteroids, such as prednisone

• Anti-inflammatories, such as firocoxib

• Antibiotics, such as doxycycline

• Chemotherapy, such as doxorubicin

• Antihistamines, such as hydroxyzine

• Antifungals, such as itraconazole

• Antiparasitics, such as fluralaner

• Professional dental cleaning (may include tooth removal)

• Abscess drainage and supportive care

Some dogs who are critically ill need hospitalization and supportive care to help them recover.

Recovery and Management of Swollen Lymph Nodes in Dogs

Dogs with swollen lymph nodes due to an infection or inflammation recover once treatment has been completed. Lymph nodes generally return to their normal size within two to four weeks following completed treatment.

However, dogs with lymphoma generally die of the disease within a year of diagnosis. Even during treatment with chemotherapy, swollen lymph nodes may not return to normal size.

Prevention of Swollen Lymph Nodes in Dogs

Many cases of swollen lymph nodes in dogs are not preventable. Even mild stimuli, like allergens, can cause lymph nodes to become larger than normal.

Making sure your dog gets regular preventative care is important so that a veterinarian can find any health concerns, such as dental disease or external parasites, that can result in swollen lymph nodes early on.

Likewise, keeping your dog on year-round flea and tick preventatives can protect him against parasites that carry diseases that can lead to swollen lymph nodes.