Why atopic dermatitis challenges everyday practice
Canine atopic dermatitis (CAD) is a genetically predisposed inflammatory and pruritic skin disease, associated with IgE antibodies directed mainly at environmental allergens. It is one of the most common skin diseases in small animal practice and, being chronic and relapsing, it tends to test the patience of both the veterinarian and the animal's owner.
The core difficulty is that CAD has no single confirmatory test. The diagnosis is clinical and one of exclusion: it relies on recognizing the pattern, ruling out look-alikes and demonstrating the response to management over time.
Clinical signs and distribution pattern
Pruritus is the central clinical sign and usually precedes visible lesions. The owner's first complaint is often licking, chewing the paws, rubbing the face or scratching the ears.
The distribution is quite characteristic and helps steer the reasoning:
- Face: periocular, perioral and muzzle regions
- Ear pinna and canal: recurrent otitis is frequently the first manifestation
- Paws: ventral surface, interdigital spaces (erythema and saliva staining)
- Axillae, groin and ventral abdomen
- Elbow flexure and perianal region
Age of onset is typically between 6 months and 3 years. Breeds such as French Bulldog, West Highland White Terrier, Labrador, Golden Retriever and Shar-Pei appear frequently, although any dog can develop the disease.
Favrot criteria: organizing the suspicion
The Favrot criteria for canine atopic dermatitis are a widely used clinical support tool to structure the suspicion. They gather findings such as early onset, a predominantly indoor animal, corticosteroid-responsive pruritus, a lesion pattern on the front paws and ear pinnae, and the absence of involvement of the ear margins and the dorsolumbar region.
It is worth reinforcing: the criteria raise or lower the probability, but do not replace the exclusion of differentials. They are a starting point for reasoning, not a diagnostic stamp.
Differential diagnosis: what to rule out first
Before assuming CAD, it is mandatory to rule out causes of pruritus that mimic the condition:
| Differential | How to approach it |
|---|---|
| Ectoparasites (sarcoptic mange, Demodex, fleas) | Skin scrapings, therapeutic antiparasitic trial, strict flea control |
| Flea allergy dermatitis (FAD) | Dorsolumbar and tail-base distribution; response to flea control |
| Adverse food reaction (food allergy) | Elimination diet with hydrolyzed or novel protein for 8 to 12 weeks, followed by a provocation challenge |
| Secondary infections (Staphylococcus, Malassezia) | Skin and ear cytology; they often coexist and perpetuate the pruritus |
Cytology is, in practice, one of the highest value tests: fast, in-office, and able to change immediate management by revealing pyoderma or Malassezia overgrowth that must be treated before any judgment about allergic control.
The elimination diet deserves emphasis because food allergy is clinically indistinguishable from environmental CAD — only a well-conducted dietary trial, free of treats or contamination, separates the two.
Multimodal, long-term management
CAD is controlled, not cured. A realistic plan combines several fronts and must be adjusted at each reassessment:
- Flare control: short-course topical or systemic corticosteroid, oclacitinib or specific immunotherapy as appropriate. The goal is to break the itch-inflammation cycle quickly.
- Treating secondary infections: cytology-guided antibiotic or antifungal; without this, no allergic control works.
- Skin barrier repair: bathing with appropriate shampoos, essential fatty acids (omega-3 and omega-6) and topical moisturizers.
- Ongoing environmental and antiparasitic control: fleas and mites kept under control year-round.
- Maintenance therapy: allergen-specific immunotherapy, oclacitinib, ciclosporin or anti-IL-31 monoclonal antibody, according to individual response and tolerance.
The key to success is continuity: documenting the response to each protocol, recording seasonal triggers and measuring the evolution of pruritus at every recheck. It is precisely in the longitudinal data that CAD management is won or lost.
Where structured records make the difference
Chronic cases like CAD live on history. Knowing which antibiotic has already been used, for how long, which elimination diet was tried and how the pruritus responded turns the recheck into a clinical decision rather than a fresh start. A well-recorded, searchable history is what sustains the reasoning across months of follow-up — and protects the owner and the patient from protocols repeated without criteria.
Conclusion
Canine atopic dermatitis is a diagnosis of pattern and exclusion, not of a single test. Recognizing the classic pruritus distribution, applying the Favrot criteria prudently, ruling out ectoparasites, food allergy and secondary infections, and offering continuous multimodal management is the path that separates sustainable control from recurring frustration. And, like any chronic disease, it rewards those who keep an organized and accessible clinical record.
