BACKGROUND: an imbalance of the intestinal microbiota can cause health problems in the gastrointestinal tract and in other organs. Canine Atopic Dermatitis (CAD) is a genetically predisposed, inflammatory and pruritic allergic skin disease with multifactorial etiology and multimodal treatment. The aim of this study was to assess the effect of a nutraceutical product on Dysbiotic Index (DI) and the skin lesions of atopic dogs. METHODS: a nutraceutical product was administered to 32 dogs with CAD. The product was associated with a standardized hypoallergenic diet for 60 days; the dietary regimen continued for 120 days, while ongoing therapies remained unchanged. Values of Visual Analogic Scale (VAS), Canine Atopic Dermatitis Lesional Index (CADLI) and DI were evaluated on day 0, 60, 120. RESULTS: all the 32 dogs showed a statistically significant decrease ( < 0.001) to V60 of VAS and CADLI, which persisted and increased to V120 when diet alone was continued. The decrease in the DI value was also statistically significant ( < 0.001). CONCLUSION: the intake of nutraceutical associated with diet resulted in a decrease in the index of intestinal dysbiosis, with an improvement in the subjective severity of cutaneous lesions.