Swollen Lymph Nodes in Dogs

Swollen lymph nodes in dogs are called lymphadenopathy. Lymph nodes are small immune-system structures that help filter fluid and respond to infection, inflammation, and abnormal cells. In many dogs, the easiest nodes to feel are under the jaw, in front of the shoulders, in the armpits, and behind the knees. When they enlarge, they may feel like firm or rubbery lumps under the skin.

This symptom matters because it can happen with a wide range of problems. Some are localized and treatable, like dental disease, a skin infection, or an abscess near the draining area. Others are body-wide illnesses, including tick-borne infections, immune-mediated disease, fungal disease, or cancer such as lymphoma. A swollen node may be painful with infection, but cancerous nodes can be painless, so comfort level alone does not tell you the cause.

Pet parents sometimes notice only one enlarged node, while others find several at once. Generalized enlargement of multiple lymph nodes raises more concern for a systemic problem. Your vet will look at the pattern, how quickly the swelling appeared, whether the nodes are painful, and whether your dog also has fever, weight loss, low appetite, coughing, lameness, vomiting, diarrhea, or skin changes.

Because swollen lymph nodes are a sign rather than a disease, the next step is finding the reason behind them. Early evaluation helps your vet sort out whether this is a short-term inflammatory issue, an infection that needs treatment, or a more serious condition that needs a broader plan.

One common cause is infection near the affected node. Dogs with dental disease, oral infections, tonsil problems, skin wounds, ear disease, or abscesses may develop enlargement of nearby lymph nodes as the immune system reacts. Tick-borne and other infectious diseases can also cause lymphadenopathy, sometimes along with fever, lethargy, poor appetite, or shifting leg lameness. In some regions, fungal and bacterial infections are also part of the workup.

Inflammation without a clear infection is another possibility. Allergic skin disease, immune-mediated conditions, and some inflammatory disorders can make lymph nodes enlarge. These cases may come with itchy skin, joint pain, recurrent fevers, or other body-wide signs. Your vet may need bloodwork and targeted testing to separate inflammatory disease from infection or cancer.

Cancer is an important cause to rule out, especially when multiple peripheral nodes are enlarged, firm, and not painful. Lymphoma is one of the best-known causes, but metastatic cancer from another site can also spread to regional lymph nodes. Dogs with lymphoma may have enlarged nodes in the neck, shoulders, groin, or behind the knees, and some also develop weight loss, low appetite, increased thirst, or breathing changes if internal organs are involved.

Less common causes include brucellosis in certain breeding dogs, leptospirosis in sick dogs with kidney or liver signs, and other systemic illnesses. The exact cause depends on your dog’s age, vaccination status, travel history, parasite exposure, reproductive status, and the pattern of lymph node enlargement.

See your vet immediately if your dog has swollen lymph nodes plus trouble breathing, collapse, marked weakness, pale gums, severe vomiting, severe diarrhea, or a very swollen face or neck. Emergency care is also important if the swelling appeared quickly after a bite, sting, trauma, or exposure to a toxin, or if your dog seems painful and cannot rest comfortably.

For dogs who otherwise seem stable, schedule a prompt visit within 24 to 72 hours if you notice a new lump where a lymph node sits, especially if more than one node feels enlarged. A node that keeps growing, feels firm and fixed, or does not improve after a few days should not be watched at home for long. Painless swelling still needs attention because lymphoma and some other cancers may not hurt early on.

You should also call your vet sooner if your dog has fever, low appetite, weight loss, bad breath, dental pain, skin wounds, limping, coughing, or recent tick exposure. These clues can help narrow the cause and may change how urgently your dog should be seen.

If your dog has a possible zoonotic infection, such as leptospirosis, use good hygiene until your vet advises otherwise. Wear gloves when cleaning urine or accidents, wash hands well, and keep other pets and people away from contaminated areas.

Your vet will start with a hands-on exam and a history. They will note which lymph nodes are enlarged, whether the swelling is localized or generalized, and whether the nodes are painful, soft, firm, or freely movable. They will also check the mouth, skin, ears, chest, abdomen, and temperature, because the source may be a nearby infection or a body-wide illness.

A fine-needle aspirate is often the first diagnostic step. This test uses a small needle to collect cells from the enlarged node and is commonly done during the visit. It can help distinguish reactive inflammation from lymphoma, metastatic cancer, or infection. Depending on the sample, your vet may review the slide in-house or send it to a pathologist. If results are unclear, a biopsy, flow cytometry, or other advanced testing may be recommended.

Bloodwork is commonly added, including a complete blood count and chemistry panel. These tests can look for inflammation, anemia, platelet changes, kidney or liver involvement, and clues pointing toward infection or cancer. Infectious disease testing may be recommended based on region and risk, such as tick-borne disease panels, leptospirosis testing, or brucellosis testing in appropriate cases.

Imaging may also be part of the plan. Chest radiographs and abdominal ultrasound can help your vet look for internal lymph node enlargement, organ involvement, masses, or other complications. The exact workup depends on your dog’s exam findings, how sick they are, and what level of information is needed to guide treatment decisions.

Do not try to treat swollen lymph nodes at home without veterinary advice. Human pain medicines, leftover antibiotics, and steroids can all create problems. Steroids are especially important to avoid unless your vet directs them, because they can interfere with diagnosing lymphoma and may temporarily shrink nodes without treating the real cause.

At home, focus on observation and comfort. Check whether the swelling is under the jaw, in front of the shoulders, in the armpits, or behind the knees, and note whether one or several nodes feel enlarged. Watch your dog’s appetite, energy, breathing, drinking, urination, stool quality, and comfort when chewing or swallowing. If your dog has skin wounds, keep them clean and prevent licking until your vet examines them.

It helps to keep a simple log with dates, photos, and notes about node size or new symptoms. This can be very useful if the swelling changes quickly or if your dog is being monitored after treatment. If your vet has started medication, give it exactly as directed and finish the full course unless your vet tells you to stop.

Call your vet sooner if the nodes enlarge rapidly, your dog stops eating, develops fever, starts coughing, seems painful, or has vomiting, diarrhea, or weakness. Home monitoring supports care, but it does not replace a diagnostic plan when lymph nodes are enlarged.