An abscess, or localized infection of the skin, between the toes is also called an interdigital furuncle. It is similar to a severely infected pimple or boil on the face. These painful, pus-filled blisters often occur in the webbing between a dog’s toes.
The most common cause of furuncles between the toes is a deep bacterial infection. Many dog breeds (for example, Chinese Shar-Peis, Labrador Retrievers, and English Bulldogs) are predisposed to the condition because they have short, bristly hairs on the webbing between the toes and/or prominent amounts of webbing. The short hair shafts are easily forced backward into the hair follicles while the dog is walking. Ingrown hairs are very inflammatory in the skin, and secondary bacterial infections are common. Less commonly, a hair shaft can become infected if foreign material, such as a splinter or burr, becomes embedded in the skin.
Early signs of infected hair follicles that could become furuncles are rash-like redness and small bumps in one spot or over the entire webbing between the toes. If left untreated, the bumps will rapidly develop into shiny, reddish purple boils 0.4 to 0.8 inches (1 to 2 centimeters) in diameter. The boils may rupture when pressed and leak bloody fluid. Furuncles are usually painful, and the dog may be obviously lame on the affected foot (or feet) and lick and bite at them. Furuncles caused by a foreign object are usually solitary and often occur on a front foot. Recurrence is not common. If a bacterial infection is causing the problem, there may be several furuncles with new ones developing as others heal.
Diagnosis is often based on signs alone. Tests to confirm the presence of inflammation and to look for parasites are often helpful. Bacterial cultures may be done to choose an appropriate antibiotic. Any abnormal growths may need to be biopsied. The furuncles can be lanced to find and remove any foreign objects. Furuncles between the toes respond best to a combination of treatment at the site and system-wide (oral) drugs. Antibiotics are frequently prescribed for an initial course lasting 4 to 6 weeks. However, because it may be difficult for antibiotics to penetrate these furuncles, more than 8 weeks of antibiotic treatment may be needed. Additional treatment for secondary fungal infections may be required. Other commonly recommended treatments include soaking the foot in warm water (with or without an antibiotic solution added to the bath) and applying antibiotic ointment. Some dogs may benefit from antibiotic wraps and bandaging. Pain medication may be needed in some dogs.
Using antibiotics improperly, such as not finishing the entire prescription, can lead to longterm, recurring furuncles between the toes. Furuncles can also recur if the bacteria are not susceptible to the antibiotic prescribed. If furuncles recur in spite of proper treatment, it may be a sign of an underlying disease (such as parasites, hypothyroidism, or fungal infection). Furuncles in confined dogs are likely to recur unless the dog is removed from wire or concrete surfaces. In some longterm cases, surgical excision or surgical correction of the webbing may be needed. The most common causes of recurrent furuncles in dogs are atopy and demodicosis.
Cysts (pockets of fluid or other material under the skin) or comedones (clogged hair follicles) also occur on the webbing between toes. Affected dogs may limp and have draining sores between their toes. Multiple clogged follicles may be seen, along with hair loss and thickened skin. Biopsy is necessary to diagnose interdigital cysts or comedones. Laser therapy can be used to successfully treat this condition. Antibiotics may be necessary to treat bacterial infections that also develop. Frequent bandage changes or other treatments may also be required.
Also see professional content regarding interdigital furunculosis.