An interdigital furuncle is a painful bump in the skin between a dog’s toes. It forms when a hair follicle there becomes infected, swells and bursts, so the infection reaches the deeper layers of the skin. Vets call this a deep pyoderma, a bacterial infection that goes deeper than the hair follicle [1].
These bumps are often called “interdigital cysts”, but the name is misleading. Most of them are inflamed, infected follicles that have ruptured, not true cysts [1]. Plugged follicles and real cysts can form between the toes in some dogs, and they are covered further down [2].
See your vet if your dog has a painful bump between the toes or is limping on a foot. Leave opening or draining the bumps to your vet.
For other paw problems, see dog paw problems. For skin infections elsewhere on the body, see pyoderma in dogs.
Signs
The University of Minnesota dermatology handbook describes these signs between the toes [1]:
- red, inflamed small bumps and larger lumps;
- blood-filled blisters;
- over time, small openings (draining tracts) that leak a bloody, pus-like fluid when the follicles burst;
- sores that wear away the surface of the skin;
- in long-standing or severe cases, a swollen paw.
One paw or several can be affected. The bumps are often painful, and a dog may lick the paw or limp in severe cases [1].
The number of paws involved can be a clue. A problem in a single paw may point to a foreign body, a local injury or a growth rather than a general infection [1].
Causes
In dogs, skin infections like this are almost always secondary. Something else weakens the skin first and gives bacteria a way in, and that trigger has to be found and managed to stop the problem coming back [1]. Staphylococcus bacteria are by far the most common cause of skin infection in dogs [1].
Triggers that can play a part include:
- Uneven weight on the paws. Many cases start because a dog puts abnormal weight on one or more paws, for example from joint disease such as arthritis or a knee ligament problem, or from carrying too much weight. This leads to many plugged hair follicles between the pads, which can become inflamed and burst [1].
- Hair under the skin. When a follicle bursts, bits of hair end up in the deeper skin. The body treats them as foreign material, which keeps the inflammation going, so these cases may only partly respond to treatment for the infection [1].
- Allergies. Allergic skin diseases, including environmental, food, flea and contact allergies, are common triggers for skin infection in dogs [1]. See seasonal allergies in dogs.
- Mites. Demodicosis, a skin disease caused by Demodex mites, is one of the parasite problems that can set up skin infection and can look like this condition [1].
- Rough surfaces. Wear and pressure on the skin under the paw seemed to contribute to plugged follicles and cysts in one study of dogs with recurrent paw lesions [2].
- Whole body diseases. Hormone diseases such as an underactive thyroid can also make dogs more likely to get skin infections [1].
Which dogs get them
Any dog of any age, sex or breed can get deep infection between the toes. It is seen more often in short-coated dogs, such as English and French Bulldogs, Staffordshire Bull Terriers and mastiff types [1].
Dogs that carry extra weight, or that walk unevenly because of joint or bone problems, put more strain on the skin between the pads and are more likely to develop the plugged follicles that lead to these bumps [1].
A related problem: comedones and cysts on the paw
Some dogs develop plugged hair follicles (comedones) and true follicular cysts in the skin between the toes. A study of 28 dogs with lameness, pain, lumps or draining tracts between the toes that kept coming back, and that had not cleared with antibiotics, found these plugged follicles and cysts on the underside of the paw. The skin there could also look bald and thickened, like a callus [2].
Your vet may suggest a skin biopsy to look for this, especially if the bumps do not respond to treatment [1][2].
How vets diagnose it
The diagnosis starts with the history and what your vet sees on the paw [1]. Your vet may also:
- take skin scrapings to check for Demodex mites [1];
- look at fluid from the draining tracts or sores under a microscope [1];
- grow the bacteria in a lab to find out which medicines will work against them [1];
- take a skin biopsy if the bumps do not respond to treatment, to rule out other causes such as fungal infection, a foreign body or a tumor [1];
- look for an underlying trigger, such as an allergy, a hormone disease or a problem with how the dog bears weight [1].
Treatment
Your vet chooses the treatment. Deep infections are usually treated with medicine by mouth chosen from lab test results, and treatment continues until every bump has healed [1]. Your vet will want to recheck your dog before stopping [1].
Soaking the feet in an antiseptic can help remove discharge and crusts, but on its own it does little against the deep infection [1].
When uneven weight bearing is part of the problem, the bumps may only partly improve, and some dogs need surgery [1]. Laser surgery to remove the affected follicles and cysts is one option for bumps that keep coming back; in the study above, the lesions cleared in most of the dogs followed up [2].
Finding and managing the trigger matters, because it is what keeps the infection coming back [1].
At home, as directed by a vet:
- bathe or soak the feet only in the way your vet shows you [1];
- give every dose your vet prescribes and do not stop early, even when the paw looks better [1];
- if your dog lives in a kennel or run, ask your vet about the floor [2];
- keep your dog at the weight your vet recommends [1];
- go back for every recheck [1].
Outlook
Outcomes vary between causes:
- When an underlying trigger is found and managed, there is a better chance of stopping the bumps from coming back [1].
- Dogs whose bumps are linked to uneven weight bearing, or to hair fragments in the deep skin, may only partly respond to treatment for the infection [1].
- In the laser surgery study, 25 of the 27 dogs followed up had their lesions clear, while 2 kept developing cysts [2].
These are statements about groups of dogs. They cannot predict how one dog will do. Your vet can explain what this means for your dog.
When to see your vet
See your vet if your dog has:
- redness or small bumps between the toes [1];
- a painful lump or blood-filled blister between the toes [1];
- a bump that breaks open and leaks bloody fluid [1];
- limping on a foot, or licking at the feet [1];
- draining sores between the toes [1][2].
FAQ
Is it a cyst?
Usually not. Most of these bumps are infected hair follicles that have burst [1]. True cysts between the toes do occur in some dogs, and a biopsy can show them [2].
Why does it keep coming back?
Infection between the toes is usually set off by something else, such as an allergy, mites, a hormone disease or uneven weight on the paws [1]. Hair fragments left in the skin and plugged follicles or cysts can also keep it going [1][2]. Your vet looks for the trigger.
Can I pop or drain the bump myself?
No. A single bump may hide a foreign body or another cause that your vet needs to check [1]. Leave it to your vet.
The bottom line
An interdigital furuncle is a painful, deep infected bump between the toes, often wrongly called a cyst. It is usually a sign that something else, such as an allergy, mites or extra strain on the paws, has opened the door to infection. A single affected paw can point to a foreign body or injury. Your vet looks for the trigger and treats the infection until every bump has healed, so see your vet and follow the plan to the end.
This article is for general information only and does not replace advice from your veterinarian. If your dog has a painful bump between the toes or is limping, see your vet.
Sources
- Torres SMF. 1.1 Canine Pyodermas. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. Licensed CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/canine-pyodermas/
- Duclos DD, Hargis AM, Hanley PW. Pathogenesis of canine interdigital palmar and plantar comedones and follicular cysts, and their response to laser surgery. Veterinary Dermatology. 2008;19(3):134-41. PubMed abstract. https://pubmed.ncbi.nlm.nih.gov/18477329/