Incidence Rate of Otitis Externa Episodes in Atopic Dogs Is Reduced by a Therapeutic Diet in a 6-Month Randomised, Blinded, Controlled, Clinical Trial.

Background: Recurrent otitis externa (OE) episodes commonly affect dogs with canine atopic dermatitis (cAD) despite ongoing cAD treatment.

Objective: To determine if a therapeutic diet with active ingredients targeting the skin barrier and allergy pathways reduces the incidence rate of OE.

Animals, materials and methods: Thirty-four client-owned dogs with active erythroceruminous OE + cAD (not necessarily active) were randomised to test (n = 16) or control diet (n = 18), fed for up to 6 months. Dogs had to be in remission by Month (M)1 after initial OE treatment. Outcomes included incidence rate (percentage of dogs with ≥ 1 OE episode), 0-3 Otitis Index Score (OTIS-3), cAD Extent and Severity Index, 4th iteration (CADESI-04), and medication score (medication required to control OE and/or cAD) at M3 and the end-point, defined as each dog's last on-study data.

Results: The incidence rate was significantly lower in the test versus control group (25% vs. 61%, p < 0.01). OTIS-3 and CADESI-04 improved significantly between baseline and M3 in both groups (control: p = 0.003 and p < 0.001; test: each p = 0.001). Between M3 and the end-point, OTIS-3 and CADESI-04 rebounded significantly in the control (p = 0.025 and p = 0.026) and not in the test group (p = 0.139 and p = 0.909). CADESI improvement from baseline was maintained at the end-point in the test (p < 0.001) and not in the control group (p = 0.227). Medication score improved significantly throughout the diet duration in the test group (baseline to M3, M3 to end-point, and baseline to end-point) versus no improvements in the control group.

Conclusion and clinical relevance: A therapeutic diet for cAD helped to sustain improvements in aural manifestations.