My Dog’s Lymph Nodes Are Swollen

Finding a new lump on your dog can make your stomach drop. I get it. As a veterinary assistant, I have seen how quickly worry spirals when someone notices swelling under the jaw, in front of the shoulders, or behind the knees. The good news is that swollen lymph nodes are not a diagnosis. They are a clue. And with a calm, step-by-step approach, you and your veterinarian can usually figure out what is going on.

This article will help you understand what swollen lymph nodes can mean, where to check, what else can mimic a lymph node, when to seek urgent care, and what your vet may recommend next.

What lymph nodes do (and why they swell)

Lymph nodes are small, bean-shaped structures that act like “filter stations” for the immune system. They help trap and process things the body wants to respond to, such as bacteria, viruses, inflammatory debris, and abnormal cells.

When lymph nodes swell, it often means one of these is happening:

• Reactive swelling: The node is doing its job because of an infection, inflammation, allergies, or dental disease nearby.
• Infection inside the node: Less common, but possible. This is called lymphadenitis and can happen with certain bacterial infections and, in some regions, some fungal infections.
• Cancer: Some cancers can start in lymph nodes (like lymphoma) or spread to them.

Swelling can be localized (one region) or generalized (multiple lymph nodes throughout the body). That pattern matters and helps guide what your veterinarian looks for.

Where to look

Dogs have lymph nodes throughout the body, but these are the ones you are most likely to feel:

• Mandibular: Under the jawline, near the throat area.
• Prescapular: In front of the shoulders.
• Axillary: In the “armpit” area (harder to feel in many dogs).
• Inguinal: In the groin (can be confused with mammary tissue in females).
• Popliteal: Behind the knees, along the back of the hind legs.

A normal lymph node is often small and can feel like a soft pea or bean, depending on your dog’s size. When enlarged, they can feel more obvious, firmer, and sometimes warm or tender.

One important note: there are also normal salivary glands under the jaw that can feel like firm, smooth lumps. Many owners mistake these for swollen lymph nodes. A veterinarian can usually tell the difference quickly on exam.

Also, if your dog is overweight or has a thick coat, some nodes may be difficult to find even when they are normal.

What can mimic a swollen lymph node?

Not every lump is a lymph node. Some common look-alikes include:

• Salivary glands: Often felt under the jaw and commonly mistaken for lymph nodes.
• Cysts, abscesses, and infected wounds: These may feel warm, tender, or squishy, and sometimes come with redness.
• Fatty masses (lipomas): Usually soft and movable, often not painful.
• Benign skin growths: Such as warts or skin tags.
• Mammary tissue or mammary tumors: Can be felt near the groin, especially in females.
• Neck masses: Thyroid area masses are less common, but they can be mistaken for “a swollen node” by location alone.

This is another reason it helps to get hands on with your vet early. Location is useful, but it is not a diagnosis by itself.

Common causes

1) Dental disease or mouth infections

Swelling under the jaw is commonly linked to gum disease, infected teeth, oral wounds, or foreign material stuck in the mouth. Bad breath, drooling, pawing at the mouth, or chewing differently than usual are common clues.

2) Skin infections, wounds, or allergies

If your dog has a hot spot, ear infection, itchy allergic skin, or an abscess, nearby lymph nodes may enlarge. For example, an ear infection may go along with swelling under the jaw.

3) Tick-borne illness and other infections

Depending on where you live and what your dog is exposed to, infections such as ehrlichiosis or anaplasmosis (and other regional diseases) can cause generalized lymph node enlargement, fever, and low energy. That said, signs vary, and lymph node swelling is not always present.

4) Vaccine response

Occasionally, lymph nodes near a vaccination site may swell briefly as the immune system responds. This is typically mild and short-lived, often improving over several days to about 1 to 2 weeks. Any swelling that lasts longer, grows, or worries you should be checked.

5) Immune-mediated inflammation

Some immune system conditions can cause lymph nodes to enlarge as part of a broader inflammatory process. Your veterinarian will look at the full picture, not just the lump.

6) Cancer (including lymphoma)

This is the possibility everyone worries about. Lymphoma often causes multiple lymph nodes to become enlarged, sometimes quickly, and often on both sides of the body. Many dogs still eat and act fairly normal at first, so it is worth taking new swelling seriously even if your dog seems “fine.”

When it is an emergency

Some situations need same-day veterinary care or an emergency visit. Seek help quickly if you notice:

• Difficulty breathing, noisy breathing, or blue-tinged gums
• Trouble swallowing or excessive drooling with distress
• Rapidly enlarging swelling of the neck or face
• Fever, collapse, extreme weakness, or pale gums
• Significant pain when touched
• Swelling plus vomiting or diarrhea, especially if severe, persistent, or your dog seems dehydrated

If you are unsure, call your veterinarian or an emergency clinic. It is always okay to ask, “Does this sound urgent?”

What you can do at home

1) Do a gentle lump check and take notes

Before the vet visit, you can gather helpful details without poking too much. Write down:

• Location: under jaw, in front of shoulder, behind knee, etc.
• Size: compare to a pea, grape, walnut
• Number: one lump or several
• Firmness: soft, rubbery, firm
• Movement: does it move under the skin or feel fixed
• Timeline: when you first noticed it and whether it is changing

Tip: Take a clear photo of the area and note the date. If your dog tolerates it, you can also measure with a soft tape measure.

2) Check for other signs

These symptoms help your vet narrow down causes:

• Low appetite or picky eating
• Weight loss
• Low energy
• Fever (if you have a pet thermometer and know how to use it safely)
• Coughing or sneezing
• Bad breath, drooling, or mouth pain
• Skin redness, itching, scabs, or ear debris
• Increased drinking or urination

3) Avoid home medications unless your vet directs it

Please do not give leftover antibiotics or human pain meds. Many human medications are dangerous for dogs, and inappropriate antibiotics can complicate diagnosis.

What your veterinarian may do

In clinic, your veterinarian will likely start with a full-body exam and then recommend targeted tests based on what they find. Common next steps include:

Fine needle aspirate (FNA)

This is one of the most useful first tests for enlarged lymph nodes. A small needle collects cells from the node, which are examined under a microscope. It is quick, often minimally uncomfortable, and can sometimes provide answers the same day (if reviewed in house) or in a few days if sent to a lab.

Bloodwork

A complete blood count and chemistry panel can show signs of infection, inflammation, anemia, or organ stress. Your vet may also recommend tick-borne disease testing depending on risk and symptoms.

Urinalysis

This helps assess hydration, kidney function, and signs of infection or systemic disease.

Imaging

X-rays or ultrasound may be suggested if your vet is concerned about internal lymph nodes or organs such as the spleen and liver.

Biopsy

If FNA is inconclusive or suspicion remains high, your veterinarian may recommend a biopsy for a more definitive diagnosis.

How long is too long?

If you find a new, clearly enlarged lymph node, I generally encourage people to schedule a veterinary visit soon, ideally within a few days to a week. If the swelling is growing, multiple nodes are enlarged, or your dog is acting unwell, aim for same-day care.

Sometimes nodes swell mildly from a small infection and settle down. But because enlarged lymph nodes can also signal serious disease, it is best to confirm the cause rather than hoping it passes.

Supportive care while you wait

While you work with your veterinarian on diagnosis and treatment, these basics can support your dog’s immune system and comfort:

• Hydration: encourage water intake. If your vet says it is okay, offer a little low-sodium broth that is onion and garlic free.
• Gentle nutrition: feed a highly palatable, easy-to-digest diet if appetite is low. Avoid sudden major diet changes unless directed by your vet.
• Rest: keep activity calm if your dog seems tired or feverish.
• Parasite prevention: stay consistent with tick and flea prevention as recommended by your veterinarian.

If your dog is on treatment (like antibiotics), follow directions exactly and complete the full course unless your veterinarian changes the plan.

Frequently asked questions

Can swollen lymph nodes go down on their own?

Yes, especially if they are reactive to a minor infection or inflammation. But “can” is not the same as “should ignore.” If a node is noticeably enlarged, persistent, or accompanied by other symptoms, have it checked.

Are lymph nodes always painful when swollen?

Not always. Some dogs with significant enlargement do not act painful at all, which is why observation alone is not a reliable guide.

Is one swollen lymph node less concerning than several?

A single enlarged node can point to a local issue (like a dental infection), while multiple enlarged nodes can suggest a more systemic problem. Both deserve attention.

A gentle next step

If you are reading this because you just found a lump, take a breath. Most families do not miss this because they are careless. They miss it because life is busy and dogs are fluffy. You did the right thing by looking for information.

Your best next step is simple: schedule a veterinary exam and ask whether a fine needle aspirate is appropriate. Getting clarity early can mean faster relief if it is an infection, and earlier treatment planning if it is something more serious.

If you ever feel unsure, trust your instincts. You know what “normal” looks like for your dog, and that matters.