Evidence for the Efficacy of Over-the-counter Vitamin A Cosmetic Products in the Improvement of Facial Skin Aging: A Systematic Review.

Skincare retailers sell a plethora of retinol-containing products, ranging from serums and moisturisers to masks and eye creams.The purpose of this review is to critically appraise the randomized, double-blind, vehicle-controlled trials of the use of over-the-counter retinol products in the treatment of facial skin aging in order to assess evidence regarding their efficacy.A PubMed search was conducted for relevant clinical trial publications, using the terms "retinoid," "tretinoin," "retinol," "retinal," "retinaldehyde," and "skin."Nine randomized, double-blind, vehicle-controlled clinical trials were found. Four of these trials reported no statistically significant differences between the retinol-containing treatment and vehicle. The remaining five trials provide weak evidence for retinol potentially having a mild ameliorating effect on fine facial skin wrinkle lines only. However, these five trials showed major methodological flaws, which were critically analyzed in this review, calling into question the validity of any positive results.It can be suggested that, in the case of retinols, the "positive" trials should not inform clinical decision-making but rather may serve as tools for advertising. Until at least one high-quality clinical trial of retinol-containing products in the treatment of (photo-)aged skin is published, there is very little, if any, trustworthy evidence available to support the use of over-the-counter cosmetic retinol-containing products to improve the appearance of aged skin.