MALESSEZIA DERMATITIS
(Yeast Infection of the Skin)

The dark footprint-like structures seen here are the yeast organisms

WHY SUSPECT YEAST?

Yeast infections are especially itchy, crusty, and smelly. Often a dog starts with a rash or with simple itching but the skin thickens to an “elephant” skin appearance. The itch is extreme and the odor can be especially troublesome. Parts of the body or the entire body can be affected. Mostly dogs are affected but cats can get yeast infections as well. Yeasts are the spore-like forms of fungi; Malessezia dermatitis is a fungal infection of the skin.

WHERE WOULD A DOG GET A YEAST INFECTION?

Yeast happily live on most normal skin and in ears and anal glands. To get a  yeast infection, conditions on the skin surface have to change to favor the proliferation of the yeasts. The yeasts in small normal numbers are harmless but when the yeasts are present in large numbers, disease results.

So what conditions lead to a yeast proliferation? An increase in skin oils (which often occurs in an allergic flare up) would be the most common situation. Sometimes there is an immune deficiency which allows the yeast proliferation. Some animals are battling seborrhea (excessive oil production of the skin) and thus are naturally predisposed to the yeast proliferation. Some animals are actually allergic to the yeasts themselves. The most important thing to realize is that yeast infections are not contagious but they tend to recur unless the underlying allergy, seborrhea, or whatever problem is controlled.

The following breeds are predisposed genetically to yeast infections: the West Highland White Terrier, Basset hound, Cocker spaniel, Silky terrier, Australian terrier, Maltese, Chihuahua, Poodle, Shetland sheepdog, Lhasa apso, and the dachshund.

HOW IS THIS CONFIRMED?

There are several testing methods to confirm the overgrowth of yeasts:

• Impression smear (pressing a microscope slide on the skin to collect yeast organisms)
   
• Scotch tape sampling (pressing a piece of clear tape to the skin to collect yeast organisms)
   
• Skin scraping with a blade (scraping the skin with a blade to collect yeast organisms)
   
• Cotton swab (rubbing a moistened Q-tip on the skin to collect yeast organisms)
   
• Skin Biopsy (removing a small plug of skin with a biopsy punch with a local anesthetic. This is the most invasive choice but provides substantially more diagnostic information)

Very few yeasts need to be seen under the microscope to confirm yeast infection.

HOW DO WE GET RID OF IT?

Treatment can be topical, oral, or both. Topical treatment alone is not usually adequate but, since oral medications are expensive, often topical management alone is attempted first, especially if the pet is small enough for convenient frequent bathing or if only a small body area is involved. Shampoos: While degreasing shampoos such as the benzoyl peroxide (oxydex^®,
pyoben^®) and sulfur/salicylate (sebolyte^®, sebolux^®) shampoos will help remove the skin oils feeding the yeast, there are shampoos that are specifically anti-yeast.  We prefer the 4% Chlorhexidine shampoo called Chlorhexiderm Max as it both strips skin oil and kills yeast; however, other anti-yeast products include Selsun Blue, Miconazole shampoo, Nizoral shampoo, and more.  The pet must be bathed twice a week to start and the shampoo requires a 15 minute contact time (meaning do not rinse the lather for 15 minutes).

Spot Treatments: If only a small area is involved, it is probably not necessary to bathe the entire animal.  Special acetic acid wipes can be used to cleanse the affected area. Mixtures of vinegar and water can be used but the pet will develop a distinct vinegar odor.

Oral therapy: Ketoconazole (Nizoral®) rules when it comes to oral therapy. Typically a several week treatment is needed and there are numerous protocols involving different dosing schedules. Higher doses tend to be needed if recurrence is a problem.  The extreme itch usually resolves within one week.  This medication is expensive, especially in larger dogs, but often there is no way around its use.

Treatment of the Underlying cause:  It is important to realize that yeast overgrowth occurs in response to a primary problem be it allergy, seborrhea or something else. If the underlying problem is not controlled, yeast dermatitis is likely to periodically recur. 

For more information about Inhalant Allergy, click here.

For more information about Food Allergy, click here.

For more information about Flea Control, click here.