Yeast Dermatitis in Dogs

What is yeast dermatitis?

Yeast dermatitis, or Malassezia dermatitis, is a yeast infection on the skin, caused by the fungus Malassezia pachydermatis. It is a common cause of skin disease in dogs. This fungus is normally found on the skin, but when it grows abnormally, it can cause dermatitis (inflammation of the skin).

What are the clinical signs of yeast dermatitis?

The most common clinical signs of yeast dermatitis are:

• Itching and redness
• Musty odor
• Scales and crusty, flaky skin
• Thickened skin (“elephant skin”)
• Hyperpigmentation (darkly pigmented skin)
• Chronic or recurrent otitis externa or ear infections

How does a dog get yeast dermatitis?

The skin is home to many different bacteria and fungi, including yeast. Under normal circumstances, these organisms do not cause a problem, because the immune system keeps them under control. If conditions on the skin change or if the immune system is suppressed, these bacteria and fungi can multiply and cause infection. If the number of yeast organisms on the skin increases, the resulting overgrowth can cause yeast dermatitis. 

A common factor in a yeast skin infection is increased oil production in the skin. Increased oil production is often associated with a skin condition called seborrhea oleosa or with allergic skin disease. Yeast dermatitis is not contagious. 

Some dogs have an immune deficiency that makes their immune system less effective at fighting yeast infections, resulting in chronic yeast dermatitis infection. Dogs that receive immunosuppressive drugs, such as corticosteroids (steroids), may also be unable to effectively prevent yeast infections and may develop chronic yeast infection.

Some dogs develop a hypersensitivity to yeast, which means they become allergic to an organism they are exposed to all the time. Those dogs have an intense, inflammatory reaction with only a few yeast organisms present on their skin. They will often have frequent recurrences of yeast dermatitis, some starting shortly after treatment is discontinued.

Are some dogs more likely to develop yeast dermatitis?

Certain breeds may be genetically predisposed to developing yeast infections. These breeds include West Highland White Terrier, Basset Hound, Cocker Spaniel, Silky Terrier, Australian Terrier, Maltese, Chihuahua, Poodle, Shetland Sheepdog, Lhasa Apso, Boxer, Shih Tzu, and Dachshund.

How is yeast dermatitis diagnosed?

Your veterinarian will examine your dog’s skin and collect one or more samples to look for yeast. Several sampling techniques may be used:

• Skin scraping: Scraping the skin with a dull blade to collect yeast organisms.
• Impression smear: Pressing a microscope slide on the skin to collect yeast organisms.
• Cotton swab sample: Rubbing a moistened swab on the skin to collect yeast organisms.
• Acetate tape preparations: Applying a piece of clear tape to the skin to collect yeast organisms.
• Skin biopsy: Obtaining a small piece of skin with a biopsy punch. This test is the most invasive but provides the most complete information about changes in the skin. The sample is sent to a veterinary pathologist for examination.

Most of these samples can be examined in the clinic under a microscope by a veterinarian or veterinary technician. If yeast hypersensitivity is suspected, your veterinarian or dermatologist may recommend running blood or skin tests to confirm this diagnosis.

How is yeast dermatitis treated?

Treatment for yeast dermatitis may be topical, oral, or a combination of both, and is based on the severity and location of your dog's condition. Underlying allergies or other skin conditions must also be managed to help prevent recurrence.

Topical treatment

Treatment with medicated shampoos is a vital part of treating yeast dermatitis. Many dogs with greasy or oily skin may initially require a degreasing shampoo containing selenium sulfide or benzoyl peroxide. This treatment may be followed by an anti-fungal shampoo containing chlorhexidine, miconazole, or ketoconazole. 

It is important that the antifungal shampoo remain in contact with the skin for at least 10 minutes before it is rinsed off. To be effective, this topical treatment is required every three to five days for two to twelve weeks. If the infection is in the ears or in only a few spots on the skin, a topical medication may be prescribed for daily use.

Oral antifungal treatment

In more severe, chronic, or persistent cases of yeast dermatitis, oral antifungal medication is often required. Oral anti-fungal medications include ketoconazole, terbinafine, itraconazole, and fluconazole.

Antibiotics for secondary bacterial infections

Many dogs with yeast dermatitis also have a bacterial skin infection called pyoderma. If a bacterial infection is confirmed, antibiotics may also be prescribed. The type and duration of antibiotic treatment will depend on the infection and your dog’s response to treatment.

Monitoring and recurrent infections

Although oral antifungal medications are highly effective, they must be given for prolonged periods of time (often several months), and they may cause side effects, including effects on the liver. Your veterinarian may recommend routine blood tests, particularly if your dog requires extended treatment.

If the yeast dermatitis returns after successful treatment, your dog should be re-evaluated and the treatment plan may need to be adjusted. Most dogs with advanced or chronic yeast dermatitis are treated with a combination of oral and topical therapies.

Managing inflammation and itching

Affected dogs may also need medications, including corticosteroids (prednisone) and cyclosporine to relieve inflammation and itch while the antifungal treatment takes effect. These medications manage inflammation or underlying allergic disease and do not treat the yeast infection itself.

Immunotherapy for yeast hypersensitivity

Dogs with yeast hypersensitivity may benefit from immunotherapy. This treatment is intended to gradually reduce the immune system’s overreaction to yeast that normally lives on the skin. Immunotherapy may be given by injection under the skin or by mouth.

What is the prognosis for yeast dermatitis?

The prognosis for yeast dermatitis is generally good. While the condition usually requires long-term treatment, most cases respond favorably and the itching is reduced within a week of beginning therapy. 

In cases with underlying allergies or immune compromise, the prognosis is based on the ability to control those conditions. It is not uncommon for dogs with severe skin allergies to have recurrent secondary yeast or bacterial skin infections, sometimes two or three times a year. Your veterinarian will discuss a diagnostic and treatment plan for your dog to help you manage this condition.