Effects of Traditional Chinese Herbal Extracts on Tear Staining, Iron Status, Immune Function, and Antioxidant Capacity in Dogs

Tear staining is a common yet often underestimated condition in dogs that affects appearance and may reflect underlying disease. This study evaluated dietary supplementation with the traditional Chinese herbs Chrysanthemum morifolium (CM), Cassia semen (CS), and Poria cocos (PC) in dogs predisposed to tear staining and investigated potential mechanisms. Forty Poodle and Bichon dogs were fed diets supplemented with 0.5% CM, CS, or PC. Tear staining indices were measured biweekly, together with blood indicators of iron status, immune and inflammatory markers, and antioxidant capacity. All three supplements reduced tear staining (p < 0.05), as shown by lower scores and shorter stain length versus control. CM and PC improved iron status and porphyrin metabolism by increasing serum iron and ferritin and modulating δ-aminolevulinic acid and porphobilinogen deaminase. They also enhanced humoral immunity and antioxidant status by increasing serum immunoglobulins, reducing pro-inflammatory cytokines, and moderately improving antioxidant activities. CM and PC increased fecal Allobaculum abundance, which correlated with tear staining indices and porphyrin-related measures. In conclusion, CM, CS, and PC are promising dietary strategies for reducing tear staining in dogs, with CM and PC possibly acting via Allobaculum-associated modulation of iron and porphyrin metabolism, while improving iron status, immunity, and antioxidant defense.