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Malassezia pachydermatis Sensitivity in Dogs with Atopic Dermatitis

Darin Dell, DVM, DACVD, Wheat Ridge Animal Hospital, Wheat Ridge, Colorado


|October 2021

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In the Literature

Ishimaru H, Okamoto N, Fujimura M, et al. IgE sensitivity to Malassezia pachydermatis and mite allergens in dogs with atopic dermatitis. Vet Immunol Immunopathol. 2020;226:110070.


Malassezia pachydermatis are normal commensal organisms found on the skin of dogs, typically in the ears and near mucous membranes. Malassezia spp dermatitis describes skin infection caused by M pachydermatis, is common in all allergic dogs, and can occur in dogs with or without M pachydermatis hypersensitivity.

This study evaluated atopic (n = 15) and food allergic (n = 37) dogs to determine how many in each group were hypersensitive to M pachydermatis. Serum immunoglobulin E (IgE) measurement and intradermal allergen testing were used following standard protocols.

Results indicated that dogs with nonfood-induced atopic dermatitis were more likely to be hypersensitive to M pachydermatis than dogs with food-induced atopic dermatitis: 60% of dogs with nonfood-induced atopic dermatitis demonstrated M pachydermatis hypersensitivity via IgE testing, and results were slightly higher (73%) with intradermal allergy testing. IgE and intradermal allergy testing both revealed that 16% of dogs with food-induced atopic dermatitis were hypersensitive to M pachydermatis.

The authors hypothesized that the difference between the 2 groups was due to a faulty epidermal barrier in atopic dogs. Barrier dysfunction results in environmental allergens interacting with immune system cells in the skin, triggering inflammation.


Key pearls to put into practice:


M pachydermatis hypersensitivity is common in dogs with nonfood-induced atopic dermatitis. These dogs experience significant irritation (typically pruritus) from minor quantities of yeast on the body.


Testing skin for M pachydermatis via cytologic analysis is important to ensure appropriate treatment. It should not be assumed that every pruritic, erythematous rash is a result of bacterial pyoderma.


Topical antimicrobial treatments (eg, shampoos, sprays, mousse products) that contain chlorhexidine combined with climbazole, miconazole, or ketoconazole are an important component of lifelong allergy management. The frequency of application varies based on the formulation, but once or twice weekly is usually ideal.


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