Interdigital Cysts in Dogs: Causes, Treatment and Prevention

What Is an Interdigital Cyst?

Vets often call these lesions interdigital furuncles. Under the microscope they are pockets of deep inflammation, not fluid-filled cysts.¹ Licking or friction drives broken hairs and keratin deep into the skin, where the body reacts to them as foreign material, and bacteria then cause infection.^3,1 Less often, true cysts and blackheads (comedones) form in the skin between the toes on the underside of the paw, linked to friction and paw shape.¹

Signs

• A shiny red or purplish lump, usually 1 to 2 cm, between the toes, most often on the front paws^2,6
• A soft, squishy feel; the lump may burst and ooze bloody fluid or pus^1,2
• Limping or walking tenderly^2,6
• Licking or chewing at the paw^2,6
• Splayed toes or swelling of the paw⁶

Lumps caused by a foreign body, such as a grass seed, are usually single and often on a front foot. Lumps that keep coming back may be a sign of an underlying disease.^1,2

Causes

• Ingrown hairs and paw shape: short, bristly hairs, webbing between the toes, and wide paws that bear weight on haired skin. Excess weight and lameness add pressure.^1,2 Friction lumps most often form between the two outer toes of the front paws.^3,5
• Allergies: environmental and food allergies are among the most common triggers, and a common cause of recurrence.^4,5,1
• Mites: Demodex mites can cause or worsen paw infections.^1,2
• Foreign bodies: such as grass seeds.¹
• Hormone disease: such as an underactive thyroid.^2,5 See thyroid problems in dogs.
• Housing: living on wire or concrete floors.¹

Breeds at Risk

Short-coated, heavy or wide-pawed breeds are most often affected, including English Bulldogs, Labrador Retrievers, Shar-Peis, German Shepherds, pit bull-type dogs, Bull Terriers, French Bulldogs, Great Danes and Mastiffs.^1,5,6,3,7

Diagnosis

Vets can usually recognize these lumps on sight. Your vet may also:^1,5

• Look at fluid from the lump under a microscope (cytology)
• Send a sample for culture to find the right antibiotic
• Check skin scrapings or plucked hairs for Demodex mites
• Recommend a diet trial, allergy tests or blood tests if lumps keep coming back
• Take a biopsy of unusual or stubborn lumps
• Suggest a trial of a mite-killing medicine, because mites can be hard to find³

Treatment

• Antibiotics, ideally chosen by culture, usually for several weeks (often 4 to 8 or more). Stopping too early is a common reason lumps return.^1,2,5
• Foot soaks or medicated washes, such as chlorhexidine, as your vet directs.^1,2,5
• Treating the cause: allergy control, weight loss, managing arthritis, treating mites, and protecting paws from rough surfaces with boots.^5,3,1
• Laser or surgery for long-standing cases that don't respond to medicine. Options include laser treatment and, as a last resort, surgery that removes the diseased skin between the toes and joins the toes together (fusion podoplasty), which can shift pressure onto other toes.^4,1,5,3

Pain relief helps dogs that are limping. Ask your vet what's suitable, and don't give human medicines.^2,10

Recovery and Recurrence

Antibiotics are often given for 4 to 6 weeks at first, and more than 8 weeks may be needed.^2,5 Lumps often come back if antibiotics are stopped too early or aren't the right ones, or if an underlying problem such as environmental allergies (atopy), Demodex mites, paw shape or wire or concrete flooring isn't managed.^1,2 Managing the underlying cause long term is the best way to prevent new lumps.⁴ See also why dogs lick their paws.

Frequently Asked Questions

Will an interdigital cyst go away on its own?

They usually need veterinary treatment. Left untreated, deep infections can cause long-term pain, and lumps often come back unless the underlying cause is treated.

What happens if an interdigital cyst bursts?

It may ooze blood or pus. Keep it clean, stop your dog licking it, and see your vet.

Can I pop my dog's interdigital cyst?

No. Opening or draining it at home can lead to dangerous infections, and it is the most common mistake owners make.

How long does an interdigital cyst take to heal?

Usually several weeks with treatment. Antibiotics may be needed for 8 weeks or more in deep infections.

Are interdigital cysts painful?

Yes, they are often painful and can make dogs limp.

What does a cancerous lump on a dog's paw look like?

You can't tell by looking. Any lump that doesn't respond to treatment, grows, or keeps coming back should be sampled by your vet with a needle sample or biopsy.