Vitamin A and skin aging Original paper

Vitamin A and its derivatives (retinoids) have shown efficacy for delaying signs of skin aging.^[1] The Scientific Committee on Consumer Safety has defined safe maximum retinol concentrations as 0.05% for body lotions and 0.3% for hand, face, leave-on, and rinse-off products (other than body lotions).^[2] Since retinoid concentration in cosmetic products generally ranges from 0.0015–0.3%, determining the appropriate retinol concentration to maximize effectiveness while minimizing side effects would benefit consumers.

This randomized, double-blind study assessed a retinol cream’s efficacy and tolerability at two different concentrations, 0.15% and 0.3%. Every evening for eight weeks, 25 women applied the 0.15% cream to the left side of their face and the 0.3% formulation to the right side. The researchers completed subjective assessments before and after the study to evaluate general skin condition, hyperpigmentation brightening, skin elasticity, and wrinkle amount. Participants also completed an efficacy assessment at four and eight weeks. Thirty volunteers, separate from the main study cohort, completed an evaluation of allergenic and irritating properties of the cream.

Twenty participants ultimately completed the trial. Participants demonstrated improvements in skin color, discoloration intensity, overall skin condition, number of facial wrinkles, and skin smoothness, with no differences in any outcome between the two creams, as evaluated by the researchers’ subjective evaluations. In terms of subjective participant assessment, 60% of participants noted that their skin condition improved, and 85% and 90% noted that their skin was "smoother and more delicate to the touch" with the 0.15% and 0.3% formulations, respectively, after eight weeks. However, only 25% and 35% of participants noted improvements in skin discoloration with the 0.15% and 0.3% formulations, respectively, and no participants reported an improvement in wrinkles at the end of the study.

According to the authors, three independent researchers subjectively assessed the primary study outcomes. However, the authors did not provide details regarding evaluator blinding or other steps to ensure that evaluators were not biased in their findings.