• Malassezia dermatitis is a yeast infection of the skin.
  • It varies in severity from a mild itch to severe skin changes (in its most severe form, the skin thickens to resemble an elephant’s skin).
  • It is usually secondary to a problem such as allergies or hormonal imbalances.
  • Treatment is aimed at clearing the infection and treating the primary condition.

What Is Malassezia Dermatitis?

Malassezia dermatitis (MD) is a yeast infection of the skin caused by the organism Malassezia pachydermatisMalassezia pachydermatis is a yeast organism that normally lives in small numbers in the ears and on the skin. The infection occurs when this organism grows in large numbers. In its most severe form, the infection can cause a thickening of the skin (lichenification), making it resemble an elephant’s skin (hence the name pachydermatis).

Malassezia dermatitis generally occurs when the skin’s natural defenses break down and allow overgrowth of the skin’s normal bacteria and yeast. Sometimes, MD occurs secondary to an existing bacterial skin infection or skin allergy, as the Malassezia organism takes advantage of the skin changes that occur with these conditions. Dogs are more commonly affected by MD, but the condition can also occur in cats.

What Are the Signs of Malassezia Dermatitis?

Malassezia dermatitis can occur anywhere on the body. The condition can be confined to the ears, but other common sites include the paws, face, underside of the neck, elbows, groin, and rear. MD can cause waxy or greasy itchy skin, rashes, crusts, scales, and thickening of the skin. Sometimes the pet’s skin and ears develop a sour odor resulting from MD.

What Are the Causes of Malassezia Dermatitis?

Any disruption to the skin’s ability to keep yeast from overgrowing can lead to MD.Environmental and food allergies, greasy skin disorders (such as seborrhea), bacterial skin infections, thyroid disease, and some other medical conditions can lead to MD.

How Is Malassezia Dermatitis Diagnosed?

Once your veterinarian looks at your pet’s skin and suspects MD, diagnostics may be performed in order to confirm a yeast infection and determine the primary cause. These tests may be among your veterinarian’s recommendations:

  • Skin testing, which may include the following:
    • Adhesive tape prep: Placing a small strip of adhesive tape against the pet’s skin or fur for a few seconds permits skin cells and other debris to stick to the tape. When your veterinarian examines the tape under a microscope, bacteria, yeast, inflammatory cells, cancer cells, skin parasites, and other abnormalities can often be seen.
    • Skin scrape: By gently scraping the surface of the skin with a dull scalpel blade or similar instrument, cells just below the skin’s surface can be removed and examined under a microscope.
    • Bacterial cultureA swab of the skin (or of a pustule) can be sent to the lab to determine what bacteria are present and which antibiotics should be used to treat the infection.
    • Fungal culture: Hairs from infected skin can be sent to the lab to be tested for ringworm, MD, or other fungal infections.
    • Biopsy: After administering a local anesthetic or sedation to the patient, a small piece of skin can be removed and sent to the lab for evaluation.
  • Blood testing
    • Looks for internal reasons that the skin’s barriers to infection have broken down.
    • More extensive testing may be pursued to look for thyroid disease or other specific disorders.
  • Allergy testing
    • Determines if an allergy exists and whether specific treatment for the allergy is possible.

How Is Malassezia Dermatitis Treated?

It is very important to find the underlying cause of MD in order to keep the yeast under control. This can be difficult especially when the primary condition is resistant to treatment. Antifungal medications can be used to help decrease the numbers of Malassezia organisms on the skin and may be administered orally (as pills), topically (as an ointment or cream), or as a shampoo that your veterinarian prescribes. If the underlying cause for the MD involves a bacterial skin infection, parasites, hormonal imbalances, or allergies, these conditions must be specifically addressed to prevent recurrences. In most cases, if the primary condition is resolved, MD can be prevented from coming back.