Malassezia species are part of the normal skin flora of dogs. When the skin becomes inflamed, there is risk for bacterial or yeast overgrowth. Typical clinical signs include, but are not limited to, erythema, mild to severe pruritus, alopecia, and greasy exudation. Often an offensive rancid odor is present. The authors performed an evidence-based review of treatment protocols for Malassezia dermatitis and identified 14 different treatment protocols: 4 blinded randomized studies, 4 controlled studies lacking blinding or randomization, 5 open uncontrolled studies, and 1 descriptive study. The most common treatment protocols used single or combination therapies with ketoconazole, ketoconazole cream, itraconazole, terbinafine and cephalexin, 3% chlorhexidine shampoo, enilconazole (solution/lotion), and other shampoo therapies (including 2% miconazole/2% chlorhexidine). On the basis of the information collected and evaluated, there is good evidence to recommend 2% miconazole/2% chlorhexidine shampoo twice weekly for 3 weeks and fair evidence to recommend ketoconazole (10 mg/kg) or itraconazole (5 mg/kg), Q 24 H for 3 weeks.
COMMENTARY: The 14 studies in this paper spanned a time frame from 1994 through 2006. Over that 12-year period, much information was learned about Malassezia dermatitis. For example, at one time “Malassezia dermatitis” was considered a disease. Now, however, we recognize that skin reactions associated with Malassezia are caused by predisposing factors that allow for overgrowth and that this organism alone can cause hypersensitivity reactions. At the time many of the studies (weak as they may be) were done, treatment was based on what was currently known about a disease. In my experience, “pure” Malassezia overgrowth is uncommon and is usually associated with a concurrent bacterial infection triggered by some underlying skin disease. Both overgrowth syndromes need to be addressed, as well as the underlying cause. In my practice, it is standard to use a combined topical and systemic approach for treating bacterial and yeast infections.
Evidence-based veterinary dermatology: A systematic review of interventions for Malassezia dermatitis in dogs. Negre A, Bensignor E, Guillot. J VET DERMATOL 20:1-12, 2009.