Managing Difficult Canine Atopic Dermatitis Cases: When One Therapy Isn't Enough

A five-year-old French Bulldog with a two-year history of canine atopic dermatitis (CAD) had been receiving oclacitinib for several months. Initially, the itching improved, but the relief was short-lived. The dog returned with recurrent otitis, interdigital erythema, Malassezia dermatitis, and persistent licking of the paws. The owner believed the medication had "stopped working" and requested a stronger drug. 

Situations like this are familiar in veterinary practice. However, in many difficult CAD cases, the problem is not that the medication has failed—it is that the disease has become more complex. CAD is a multifactorial disorder involving immune dysregulation, skin barrier dysfunction, microbial imbalance, and environmental influences. Managing these patients often requires addressing several disease mechanisms simultaneously rather than relying on a single therapy¹. 

Step One: Is It Really Treatment Failure? 

Before switching medications, it is worth asking a more important question: What is driving the current flare? 

Persistent pruritus despite treatment is frequently associated with one or more of the following: 

• Secondary bacterial pyoderma 

• Malassezia dermatitis or otitis 

• Flea allergy or inadequate parasite control 

• Concurrent food allergy 

• Poor owner compliance 

• Environmental allergen exposure 

• Progressive skin barrier dysfunction 

Repeat cytology, reassessment of parasite control, dietary history, and owner compliance often reveal correctable factors that may explain why a previously effective treatment no longer appears to work². 

Why One Therapy Rarely Solves the Problem 

Current therapies target different components of CAD. 

• Oclacitinib rapidly reduces pruritus by inhibiting Janus kinase (JAK)-mediated cytokine signalling. 

• Lokivetmab specifically neutralises interleukin-31, one of the principal mediators of itch. 

• Ciclosporin suppresses T-cell activation and helps control chronic immune-mediated inflammation. 

• Glucocorticoids remain effective for acute flare management but require careful long-term use because of their adverse effects¹. 

Each therapy has clear benefits, yet none addresses every aspect of the disease. They reduce inflammation and itching but do not eliminate secondary infections, restore the damaged skin barrier, correct nutritional imbalances, or remove environmental triggers. Consequently, relying on medication alone may leave important drivers of disease progression untreated. 

Secondary Infections: The Hidden Cause of Persistent Pruritus 

One of the most common reasons for apparent treatment failure is an untreated secondary infection. 

Bacterial pyoderma and Malassezia overgrowth can significantly increase pruritus and inflammation, even in dogs receiving effective anti-pruritic therapy. Every flare should therefore prompt repeat cytology before changing systemic medication. Appropriate antimicrobial therapy based on cytological findings often restores clinical control without the need to escalate immunomodulatory treatment². 

Repair the Skin Barrier—Not Just the Immune Response 

Skin barrier dysfunction is a hallmark of CAD. A compromised barrier allows allergens, microorganisms, and irritants to penetrate the skin more easily, perpetuating inflammation and increasing susceptibility to recurrent infections². 

Barrier repair should therefore be considered an essential component of therapy. Regular bathing with appropriate therapeutic shampoos, moisturising formulations, and skin barrier repair products can reduce allergen penetration and improve skin health. 

Nutrition Is Becoming an Essential Part of CAD Management 

Nutrition is increasingly recognised as another pillar of multimodal therapy. 

Therapeutic diets enriched with omega-3 fatty acids (EPA and DHA), antioxidants, and polyphenol-rich ingredients have been shown to improve skin lesion severity and reduce pruritus when used alongside conventional treatment³. These nutrients help modulate inflammation, reduce oxidative stress, and support skin barrier integrity^3,4. 

More recent evidence suggests that dogs with CAD may also develop deficiencies in iron, zinc, and certain vitamins, even while consuming nutritionally complete diets⁴. Chronic inflammation can impair nutrient absorption and utilisation through a process known as the mucosal block, limiting the availability of essential micronutrients required for normal immune regulation and tissue repair^3,4. 

This emerging understanding suggests that nutritional management should extend beyond calorie intake and include strategies that improve nutrient bioavailability and address inflammation-associated deficiencies. 

Build a Multimodal Treatment Plan 

Rather than searching for a single "best" drug, successful management of difficult CAD cases requires combining complementary therapies. 

An effective multimodal plan may include^1,2,3,4: 

• Appropriate anti-pruritic or immunomodulatory medication. 

• Cytology-guided management of bacterial and yeast infections. 

• Strict parasite control. 

• Skin barrier repair with topical therapy. 

• Therapeutic nutrition. 

• Allergen-specific immunotherapy (ASIT) where appropriate. 

• Regular reassessment and owner education^1,2. 

Individualising treatment according to the patient's clinical presentation often produces better long-term control than escalating pharmacological therapy alone. 

A Practical Approach to the Non-Responsive CAD Patient 

When a dog fails to respond as expected, consider the following stepwise approach: 

1. Confirm the diagnosis and rule out other pruritic skin diseases. 

2. Perform repeat cytology to identify bacterial or yeast overgrowth. 

3. Review parasite control and investigate concurrent food allergy if indicated. 

4. Assess owner compliance, including medication administration and topical therapy. 

5. Evaluate skin barrier support and nutritional management. 

6. Consider combination therapy rather than immediately changing drugs. 

7. Monitor response objectively using tools such as the Canine Atopic Dermatitis Extent and Severity Index (CADESI) and owner-assessed pruritus scores¹. 

The Clinical Take-Home 

Managing difficult canine atopic dermatitis is rarely about finding a stronger medication—it is about identifying the missing piece of the puzzle. Persistent pruritus often reflects multiple concurrent problems, including secondary infections, barrier dysfunction, environmental triggers, and inflammation-associated nutritional deficiencies. By adopting a multimodal approach that combines pharmacological therapy with topical care, nutritional support, cytology-guided infection management, and regular reassessment, veterinarians can achieve more consistent long-term disease control and improve quality of life for both patients and their owners.  

References (Vancouver) 

1. Santoro D, Marsella R, Pucheu-Haston CM, Eisenschenk MNC, Nuttall T, Bizikova P. Current knowledge on canine atopic dermatitis: pathogenesis, diagnosis and treatment. Vet Sci. 2022;9(7):330. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC9204668/ 

2. Olivry, T., DeBoer, D.J., Favrot, C. et al. Treatment of canine atopic dermatitis: 2015 updated guidelines from the International Committee on Allergic Diseases of Animals (ICADA). BMC Vet Res 11, 210 (2015). https://doi.org/10.1186/s12917-015-0514-6  

3. de Santiago MS, Arribas JL, Llamas YM, Becvarova I, Meyer H. Randomized, double-blind, placebo-controlled clinical trial measuring the effect of a dietetic food on dermatologic scoring and pruritus in dogs with atopic dermatitis. BMC veterinary research. 2021 Nov 19;17(1):354. https://doi.org/10.1186/s12917-021-03063-w 
4. Frizzo-Ramos J, et al. Lymph-targeted nutritional supplementation improves clinical outcomes and reduces medication requirements in dogs with canine atopic dermatitis: a randomized, double-blind, placebo-controlled pilot study. Front Vet Sci. 2025. Available from: https://doi.org/10.3389/fvets.2025.1657869