Yeast Dermatitis in Dogs

A naturally occurring yeast, MP is a genus of fungi that exists in both healthy animals and humans. If the yeast remains in small amounts and within a proper balance, the canine is at little risk for developing infection or skin changes. However, certain conditions may lead to a rapid proliferation of the yeast, thereby causing infection. The most vulnerable dogs are those with pre-existing health conditions or an underlying immune impairment. Another cause for rapid yeast proliferation is high heat and humidity. Basically, anything that challenges a dog’s immune system or exacerbates stress places the canine at risk for yeast dermatitis.  

Factors that increase a dog’s susceptibility range from the simple to the complex.  In all dogs, including those at optimum health, MP infections may occur during the high-humidity months of the year. In addition, if the dog has a congenital or infectious disease, the weakened immune system will likely enable the beginning of a yeast infection. Hormonal imbalances also open a dog to prolific yeast growth. In addition, increased levels of sebum (a waxy substance that lubricates the skin and coat) and/or ear wax gives the perfect condition for a yeast dermatitis to occur. Dogs who are on a longer-than-normal course of certain medications, such as glucocorticoids or antibiotics, may be predisposed to an infection with this yeast.

While yeast dermatitis can occur in dogs of all ages and breeds, some breeds have increased susceptibility. Basset Hounds, Cocker Spaniels, English Setters, Maltese, German Shepherds and Shih Tzus are all examples of breeds that are predisposed to yeast dermatitis.

Malassezia pachydermatis (MP) is an ever-present yeast commonly found in dogs around the nose, mouth, ears, anus, anal sacs, vagina, armpits, between the toes (interdigital) and in nail beds. As part of the normal microflora, MP is found both on the skin surface and in the ear canals of dogs.

The most reliable and simple way to diagnose a yeast dermatitis is a positive identification of the organism under a microscope. A veterinarian will obtain samples of the infected skin by scraping and/or swabbing on skin sites or in the ear canal. Samples may also be obtained by using transparent tape. Since MP is present even on healthy animals, diagnosis may best rely on an animal’s response to topical treatment.

Any underlying disease condition must be determined and isolated to proceed with the best treatment.

To best treat yeast dermatitis, treatment usually involves a combination of systemic and topical therapy.

Systemic

For dogs with severe cases, or in those that are resistant to topical treatment, oral drugs may be prescribed. As always, these drugs must be administered per a veterinarian’s treatment plan, usually lasting one to two weeks maximum, because of potentially dangerous side effects.

Topical

Your veterinarian can guide you toward the best shampoo for your pet. Shampoos containing benzoyl peroxide and sulfur and chlorhexidine shampoos (1% or stronger) remove excess oil and lipids (fats) from the skin. In some dogs, Selsun Blue shampoo has proven effective; however, this product can irritate dogs with particularly raw skin. 

The veterinary caregiver will always prescribe a topical ointment to be applied directly to smaller infected areas which will provide relief from the irritation and itch. Your veterinarian will instruct on how to clean your pet’s ears, which may become infected due to the yeast.