Clinical evaluation of a dioic acid‐based formulation on facial skin in an Indian population

The aim of this work was to investigate the effects of 1,18‐octadecen‐9‐dioic acid (dioic acid) and a Rumex occidentalis extract complex for their skin‐lightening action in an Indian population. Prior to the clinical study, the efficacy of dioic as an inhibitor of melanogenesis was confirmed on dark‐pigmented human melanocytes. As part of a 12‐week vehicle‐controlled clinical study, the skin‐lightening effect of a test product containing 1% dioic acid, 2% of a Rumex occidentalis extract and sunscreens (SPF 15) was assessed on the facial skin of 71 Indian female volunteers. Change in skin colour was monitored by (A) Chroma Meter^® measurement (L*, a*, b*) and Individual Typology Angle (ITA?) calculation and (B) Visual grading of standardized photographs by a dermatologist. Colorimetric measurements on volunteers' cheeks showed a significant increase of L* and ITA? compared to baseline after 4, 8 and 12 weeks of test product application. For both L* and ITA? measurements, changes were significantly different than the SPF 15‐containing vehicle at weeks 4 and 12. These results were confirmed by the dermatological visual grading. The overall skin‐lightening action of the test product was beyond the one observed with the SPF 15 vehicle. These findings show that a dioic acid and Rumex occidentalis complex deliver a significant skin‐lightening effect on facial skin in an Indian population.