Clinical research demonstrates that probiotic supplementation can improve skin conditions in dogs with atopic dermatitis, which commonly features secondary yeast overgrowth. This comprehensive guide goes beyond surface-level advice to examine the biochemical mechanisms—SCFA production, HDAC inhibition, GALT immune programming, and receptor signalling—through which gut health influences skin. Featuring 15 peer-reviewed citations including 6 canine clinical trials, with evidence-based strain recommendations and an 8-16 week improvement timeline.