Yeast infections in dogs are usually in the skin and ears and are caused by an organism called Malasezzia pachydermatis or malasezzia for short. Malasezzia appeared on the dermatology scene about 10 years ago, but probably has been around a lot longer. It used to be, and still is in many dogs, a commensal-type organism, or one that is present but doesn't do any harm. A good example would be the shark and the remora. In the ears, it is considered a secondary pathogen, but in the skin it is now recognized as a primary one, although there is usually a predisposing cause that changes it from an innocent bystander into an itchy nuisance.

Most often dogs that are suffering from malasezzia have skin lesions. These lesions can be solitary (one or two), multifocal (in patches), or generalized (all over). The sores are usually red and are accompanied by areas of increased pigmentation, hair loss, and scaliness or greasiness. This scaliness and greasiness with a yellowish tint is usually the tipoff that malasezzia is the culprit. The dogs are also usually very itchy and have a musty or seborrheic-type odor. The most common sites are the underside of the neck, the belly, and the feet, especially between the toes.

So, what can cause this organism to suddenly start causing such problems? Anything that disrupts the normal coat of sebum that covers your dog's skin, that's what! Sebum is a thin layer of a waxy substance that is secreted by sebaceous glands in the skin. Allergic skin disease such as food allergy, flea allergy, and allergies to pollen, grasses, etc. can predispose dogs to malasezzia. So can an underactive thyroid gland, or hypothyroidism. A prior course of antibiotics or corticosteroids also may predispose your dog. Some breeds such as basset hounds, spaniels, poodles, and German shepherds are also more likely to get malasezzia. And, primary or secondary disorders of sebum, called seborrhea, can predispose a dog to malasezzia. Seborrhea is an entire article by itself (look for a previous article titled "Dealing with Doggy Odor" on The Pet Tribune website).

Fortunately, malasezzia is very easy to diagnose. All your veterinarian has to do is have a high degree of suspicion and then see the yeast cells on a slide under a microscope. He or she can use tape, cotton swabs, or direct smears to get the yeast on a slide and then go have a look-see!

Even more fortunate is that malasezzia is usually easy to treat. First, we need to correct any underlying problems such as allergies, thyroid problems, or seborrhea. Then, unless we have a very serious case I advocate trying topical therapy before using oral medications. Topical therapies consist of shampoos, rinses, and sprays. They usually will have one or more of the following ingredients: miconazole, ketaconazole, chlorhexidine, acetic acid, or even selenium disulfide. Topical therapy must be used two to three times a week for six weeks. Oral therapy is preferred by most dermatologists (probably because by the time they see a case it is bad!) with topical treatment used to help both the course of the disease and also to make your dog feel better instantly! Oral therapy consists of one of the anti-fungal drugs like ketaconazole, itraconazole, or fluconazole. They can be costly, and your dog's liver will have to be monitored with blood tests, but they are very effective.

If your pet has skin problems and has the hallmark signs of a waxy, yellow, smelly discharge on the skin, think yeast. Make sure you try to identify an underlying cause or you may be dealing with this little organism for a long time.

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-Dr. Stephen M. Sheldon Sheldon practices at and owns Hammocks Veterinary Hospital in Miami, Fla. A University of Florida graduate, he is past president of the South Florida Veterinary Medical Association and a member of the Veterinary Cancer Society. He can be reached at (305) 388-0880. Visit his website at www.hammocksvet.com