Could My Dog Have Panniculitis?

A firm lump under your dog’s skin is easy to dismiss as a minor infection. But if it’s draining an oily or bloody discharge, or if antibiotics aren’t working, it’s worth knowing about panniculitis. Here’s what it is, what causes it, and why getting the diagnosis right matters so much.

What is panniculitis in dogs?

Panniculitis is inflammation of the subcutaneous fat, the layer of fat tissue that sits just under your dog’s skin. When that tissue becomes inflamed, it forms firm, raised lumps called nodules, most commonly on the trunk. As the condition progresses, those nodules can soften and rupture, leaking an oily or bloody fluid. In some cases, the skin over the lump breaks down entirely (ulceration).

It can look alarming, and it warrants a vet visit. But it doesn’t automatically mean infection.

Symptoms to watch for

Panniculitis symptoms are usually noticed by owners during petting or grooming.

• One or more firm, round lumps under the skin (nodules): Often on the chest, belly, or back. Any new lump that wasn’t there before warrants a vet visit within a few days, sooner if it’s growing or draining.
• Lumps that feel like they’re “moving” slightly when pressed: Sitting in the fat layer rather than attached to the surface. This is distinctive from surface-level skin lumps.
• Draining nodules that ooze an oily, greasy, or bloody discharge: If a lump is actively draining, see a vet today. This is the symptom that’s most commonly misread as a straightforward infection.
• Crusting or scabbing over a lump that has ruptured: Can develop after a nodule drains. Keep the area clean and see a vet promptly.
• Ulceration (open sores where the skin has broken down): A more advanced sign. Don’t delay if you’re seeing this.
• Scarring in areas where nodules have healed: A sign the condition may have been going on longer than you realized.
• Lethargy or reduced appetite: If systemic disease is involved. Combined with skin nodules, this warrants a same-day vet call.

Note the location and number of lumps before your appointment. The pattern can help your vet narrow down the cause.

What causes panniculitis in dogs?

There’s no single cause. Panniculitis is more of a response pattern than one specific disease.

• Idiopathic or immune-mediated: The most common form in dogs is sterile nodular panniculitis. “Sterile” means no bacteria are involved. The immune system attacks the fat tissue for reasons that aren’t always clear.
• Infection: Bacteria, fungi, or other organisms can trigger panniculitis, including in the pyogranulomatous form (a pattern involving both pus-forming and granuloma-type immune cells).
• Trauma or injection: A previous injury, surgery site, or vaccination spot can trigger localized inflammation in the fat layer.
• Pancreatic disease: Dogs with pancreatitis or pancreatic tumors sometimes develop panniculitis as a secondary effect, because enzymes released by a damaged pancreas can literally digest fat tissue.
• Nutritional deficiency: Low vitamin E levels have been linked to some cases.
• Other underlying conditions: Lupus and other systemic immune disorders can also trigger fat inflammation.

When a draining lump isn’t an infection

A draining nodule looks like an infection, but sterile panniculitis doesn’t respond to antibiotics because there’s nothing infectious to kill. The actual treatment is immunosuppressive medication, drugs that dial down the immune response that’s attacking the fat tissue. That’s the opposite of treating an abscess.

This is why a biopsy matters so much. It confirms whether the inflammation is sterile or infectious and guides the right treatment. Cytology (examining fluid from a nodule under a microscope) can provide early clues, but a biopsy gives the clearest picture. Without it, treatment is essentially a guess.

Diagnosis and treatment

Your vet will typically start with a physical exam and review of your dog’s history, then move to diagnostics. These may include:

• Cytology: A needle is used to collect fluid or cells from a nodule, which are then examined under a microscope. Quick, minimally invasive, and a good first step.
• Biopsy: A small tissue sample is removed and sent to a pathologist. This is the most definitive test for confirming panniculitis and identifying the type.
• Blood and urine tests: To check for systemic illness, pancreatic disease, or nutritional deficiencies.
• Culture: If infection is suspected, a sample may be cultured in a lab to identify the specific bacteria or fungus involved.

Once the cause is confirmed, treatment is targeted accordingly:

• Sterile or immune-mediated panniculitis: Your vet may recommend corticosteroids (like prednisone) or other immunosuppressive medications to reduce the immune response. Vitamin E supplementation has also shown benefit in some cases, particularly breed-specific or nutritional forms.
• Infectious panniculitis: Targeted antibiotics or antifungals depending on what the culture identifies.
• Pancreatic-associated panniculitis: Treating the underlying pancreatic condition is the primary focus.
• Single nodule cases: Surgical removal is sometimes sufficient if there’s only one lesion and no systemic cause is found.

Long-term management may be needed for immune-mediated cases, with medication tapered slowly as the condition responds.

Is panniculitis covered by pet insurance?

The cost of diagnosing and managing panniculitis can add up quickly, especially when biopsy, cytology, specialist consultations, and ongoing immunosuppressive medication are all part of the picture.

Panniculitis is covered under a Lemonade Pet accident and illness policy, as long as it’s not pre-existing and develops after the 14-day illness waiting period has passed. A condition like panniculitis can take months of testing and treatment to manage, and having coverage from the start means you’re not making medical decisions based on what you can afford in the moment. If your dog is currently healthy, this is a good time to get a quote.

Before we go

Finding a lump on your dog is unsettling, and a draining one is even more so. But panniculitis, even the immune-mediated kind, is a diagnosable, treatable condition. The most important thing you can do right now is get your dog to a vet and push for a biopsy if nodules are involved. A clear diagnosis is what unlocks the right treatment, whether that’s immunosuppressives, vitamin E, antibiotics, or something else entirely.

Don’t let a “try antibiotics first” approach substitute for knowing what you’re actually dealing with.

Frequently Asked Questions

A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC.  The statements do not apply to policies underwritten by other carriers.