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.