Effect of sodium bisulfate on skin and hooves of horses

OBJECTIVE: To evaluate the safety of sodium bisulfate for use in horse barn environments by determining its irritant effect on skin and hooves. ANIMALS: 6 female mixed-breed ponies. PROCEDURE: Sodium bisulfate was applied to clipped intact skin of 6 ponies to evaluate its irritant effect after single (48 hours) and repetitive (6 h/d for 10 days) applications; similar areas of skin were used as untreated control sites. In addition, sodium bisulfate was applied to the sole of both front hooves of each pony and covered with wet gauze, and the entire hoof was covered with adhesive tape for 48 hours. RESULTS: Contact with moistened sodium bisulfate for 48 hours had no effect on pony skin. Contact with sodium bisulfate for 6 hours on 10 consecutive days did not cause gross changes but did cause mild to moderate microscopic changes including epidermal necrosis, hyperkeratosis, capillary congestion, edema, and diffuse mixed inflammatory cell infiltrate. All changes were limited to the epidermis and superficial dermis. Gross changes in hoof sole, signs of lameness, and increase in digital pulse pressure or pulse intensity were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: Duration of contact with sodium bisulfate in this study was in excess of that expected under typical husbandry conditions. Despite this fact, gross changes in skin and hooves were not detected. Microscopic lesions were confined to the epidermis and superficial dermis. Results suggest that contact with sodium bisulfate under these conditions is safe.