TL;DR: Interdigital cysts are painful inflammatory bumps between a dog's toes that typically require a routine veterinary visit rather than emergency care, unless accompanied by signs of systemic illness or significant swelling.
What is an interdigital cyst and why does it form on my dog's paw?
An interdigital cyst, or interdigital furuncle, is a painful, fluid-filled bump that develops in the webbing between a dog's toes. Key characteristics include:
- These are often localized areas of deep inflammation or infection rather than true cysts.
- They are frequently caused by short, coarse hairs being pushed back into the skin.
- Bacterial infections or foreign objects like grass seeds becoming lodged in the paw can also trigger them.
Is an interdigital cyst a medical emergency for my dog?
The urgency level for an interdigital cyst is generally low, but you should monitor for specific signs to determine how quickly your dog needs to be seen:
- Schedule a routine appointment if your dog experiences discomfort, limping, or obsessive licking.
- Seek veterinary care more promptly if you notice signs of a systemic infection, such as extreme lethargy or loss of appetite.
- Contact your veterinarian if the entire limb begins to swell.
How can taking a photo of the affected paw help with my dog's triage?
Taking a clear, well-lit photo of the affected paw is one of the most helpful things you can do for your veterinary team because:
- High-quality images allow a professional to assess the color, size, and severity of the lesion from a distance.
- Visual information helps the clinic determine if your dog needs to be seen immediately.
- It helps the team decide if the issue can be managed with at-home care until a scheduled appointment is available.
Clinical Context (Merck Veterinary Manual)
Interdigital furuncles, often incorrectly called interdigital cysts, are painful nodular lesions located in the interdigital webs of dogs and represent nodular pyogranulomatous inflammation. Deep bacterial infections are the most common cause, particularly in breeds with short, bristly hairs and prominent interdigital webbing, predisposing them to traumatic implantation of hair into follicles. Canine atopic dermatitis and demodicosis may also be primary causes. Dogs with interdigital comedones and follicular cysts typically present with lameness and draining tracts, often exhibiting alopecia and thickened, callus-like skin with multiple comedones. Diagnosis is based on clinical signs, with differential diagnoses including traumatic lesions, foreign bodies, follicular cysts, and neoplasia. Diagnostic tests include skin scrapings for *Demodex* mites and impression smears or fine-needle aspirates to confirm inflammatory infiltrates.
Chapter: Dermatology
Source: The Merck Veterinary Manual, 11th Edition (Page 862)