Bacterial infections of the skin and hair follicles (pyoderma) are very common problems in our pets. They are most commonly caused by an overgrowth of the organism Staphylococcus intermedius. The infection causes a small pustule, or pimple, to form, which quickly ruptures and then forms a crust, and finally an epidermal collarette (an area of hair loss with central clearing and a peripheral ring of scale). As the lesion heals an area of darker skin (hyperpigmentation) remains. In certain breeds, the lesions appear as patches of hair loss. In other breeds, true pustules will be seen. There are many reasons that the “staph” bacteria grow and cause pyoderma. Bacteria will not usually cause disease on normal skin, but other underlying skin diseases cause some changes in the skin surface making it susceptible to infection. Common underlying causes of pyoderma include allergic skin diseases (food allergy, atopy, flea allergy), parasites (demodectic or sarcoptic mange), seborrhea, hormonal imbalances, and immune deficiencies. It is important to attempt diagnosis and treatment of the primary problem while treating the pyoderma. Unfortunately, there are certain cases where an underlying cause for the skin infection cannot he identified and treated, and therefore the skin infections are likely to be recurrent.
Antibiotics are used to treat superficial pyoderma (folliculitis) for a minimum of 21 days. Medicated shampoos containing benzoyl peroxide or chlorhexidine and leave-on conditioners are often prescribed. Topical therapy is helpful in localized areas.
Recurrent Superficial Pyoderma
Recurrent superficial pyoderma is a common and frustrating problem. Testing for underlying disorders such as hypothyroidism, Cushing’s disease, allergies, etc., are usually indicated. Often, an underlying disorder cannot be found, and therefore treatment is aimed at controlling the bacterial population. Initially, long courses of antibiotics are used. Subsequently, intermittent antibiotic therapy or low dose daily antibiotic therapy are often needed to control recurrences. Shampoo therapy can be helpful in limiting recurrences.
When the infection occurs deep in the hair follicle, it leads to rupture of the hair follicle and release of keratin into the dermis (deep layer of the skin) which causes a severe foreign body reaction. This results in inflammation (redness and swelling) and exudation (pus). Organisms besides Staphylococcus intermedius are often involved, so that culture and sensitivity testing is useful to determine the optimum treatment. The treatment must be continued for an extended period of time. The deeper the skin infection the longer the course of antibiotics that will be needed. It is important to give the full dose of antibiotics for the entire time prescribed, regardless of how much better the skin looks. The underlying skin problem may need to be corrected in some cases before antibiotics can be completely effective.
Pododermatitis is a form of deep pyoderma that affects the interdigital (between the toes) area of the paws. Skin scrapings to rule out demodicosis and cytology to look for bacteria and yeast may be performed. Oral antibiotics for several weeks are often required. Topical therapy is helpful to successfully control pododermatitis. This can include soaking the feet, shampooing the feet, and rubbing ointments into the feet. Especially helpful are foot baths where the shampoo (benzoyl peroxide or chlorhexidine) contacts the feet for 15 to 20 minutes.
Once pyoderma is controlled, maintenance therapy is often necessary to prevent recurrences.