With skin allergies accounting for the most common insurance claim for dogs for at least 13 consecutive years, and year-over-year increases in individual allergy-related claims for both dogs and cats, effective allergy management is paramount for small animal veterinarians.

Atopic dermatitis results from complex interactions among the skin barrier, skin microbiota, and skin cell populations, ultimately leading to imbalanced immune reactions, specifically amplified pro-inflammatory T helper cell type-2 (Th2) immune responses to allergens. Interleukins upregulated with Th2 responses include IL-2, IL-4, IL-5, IL-6, IL-13, and IL-31, which are responsible for atopic inflammation and pruritus.

As there are no confirmatory diagnostic tests or pathognomonic clinical signs, atopic dermatitis can only be diagnosed after ruling out or addressing secondary infections, non-allergic conditions, flea allergy dermatitis, and cutaneous adverse food reactions. Key historical features, including seasonal pruritus, onset of clinical signs between six months and four years of age, and response to antipruritic medications, may support a diagnosis of canine atopic dermatitis.

While it is not always feasible, allergen-specific immunotherapy (ASIT) should be considered and discussed in all cases of atopic dermatitis, as it is the only available etiological treatment. All other therapies manage the condition by masking the clinical signs. The mechanism of action of ASIT is poorly understood, but it is thought to reduce/prevent atopic flares by improving the balance between the T helper cell type-1 and type-2 immune responses and increasing the amount of T regulatory cells, which produce anti-inflammatory cytokines.

The goal of ASIT is to reduce or prevent atopic flares, thereby decreasing the need for medical intervention. Variable response rates are reported, but 50-100 percent are reported to favorably respond to ASIT.

The cited time between the initiation of ASIT and clinical response also varies. Clinical improvement may not be appreciated until the 12-month mark or longer, so owners are encouraged to consistently administer ASIT for at least this period. To maintain the patient's and owner's quality of life while awaiting clinical improvement from ASIT, antipruritic and anti-inflammatory treatments, as well as antimicrobials for secondary infections when present, are heavily relied upon.

One of the most important recent advancements in medicine and tools for atopic dermatitis is the Janus kinase (JAK) inhibitor.

JAKs are cell-surface receptor-associated proteins that regulate the expression of specific cytokines and growth factors via enzymatic cascades. Simply, inhibiting the JAK mechanism results in blocking the transcription of certain genes, commonly interleukins, when discussing atopic dermatitis.

The JAK family has four members: JAK1, JAK2, JAK3, and TYK2. JAK1 appears to be most important for atopic dermatitis. In human medicine, wherein there are numerous medications within this drug class available, JAK inhibitors that preferentially block a set JAK are considered "selective," while those that block multiple JAKs are considered "non-selective." Differences in selectivity affect safety and efficacy, and higher doses have been demonstrated to reduce selectivity.

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About Rebecca Parsiola, DVM, DACVD
Dr. Rebecca Parsiola earned her undergraduate degree from Louisiana State University and her Doctor of Veterinary Medicine degree from Louisiana State University School of Veterinary Medicine. She completed a rotating small-animal internship in Washington, D.C., followed by a dermatology residency at Dermatology for Animals in Phoenix, Ariz. Dr. Parsiola completed the Dermatology for Animals residency program in 2025 and earned veterinary dermatology board certification the same year. She is currently practicing at Dermatology for Animals in Rockville, Md., a Thrive Pet Healthcare partner.