Background: Onycholysis and other nail toxicities occur in approximately 20-30% of breast cancer(BC) patients receiving docetaxel(D) chemotherapy. Onycholysis, the separation of the nail plate from nail bed, is also often associated with painful paronychia decreasing patients’ the efficacy of a hydrating nail solution (EVONAIL solution, Evaux Laboratories, France) for the prevention and treatment of D-induced onycholysis and nail toxicities. Methods: This study is a prospective randomized controlled study of hydrating nail solution for prevention or treatment of onycholysis in patients with BC receiving neo/adjuvant 3-weekly D after doxorubicin plus cyclophosphamide. In experimental arm, each patient painted hydrating nail solution on nails and periungual areas once a day till developing onycholysis grade 2 or more. After Gr 2 onycholysis development, patients painted EVONAIL twice a day regardless of treatment arms. The primary endpoint is the incidence of onycholysis Gr 2 or more and recovery rate from Gr2 onycholysis. The secondary endpoints include: the incidence of all grade onycholysis; duration from first docetaxel treatment until onycholysis symptom appearance; degree of pain from nail toxicities; the incidence of other nail toxicities. Results: Since Aug 2015 to May 2016, 103 patients were enrolled and completed this study (Experimental arm(E) : 51, control arm(C): 52). Of 103 patients, 25 cases of Gr1 and 22 of Gr2 onycholysis were observed (Gr1 and 2(n,(%)) : 8(15.7%) and 7(13.7%) in E, 17(32.7%) and 15(21.4%)in C, respectively). Hydrating nail solution resulted in statistically significant reduction of Gr2 onycholysis compared to C (HR = 0.39, 95% CI 0.16, 0.96; P = 0.041) and all grade onycholysis decreased in experimental arm with statistical significance (HR = 0.37, 95% CI 0.20-0.69, P = 0.002). However, the effect of onycholysis treatment was not observed. Conclusions: Hydrating nail solution significantly reduced the incidence of D induced onycholysis in BC patients (NCT02670603). Clinical trial information: NCT02670603