Go To Post Which one to use - RETINOL or RETINOIC ACID? Sharing with you 1 interesting study comparing RETINOL vs RETINOIC ACID. "The results of this study demonstrate that topical application of retinol significantly affects both cellular and molecular properties of the epidermis and dermis, as shown by skin biopsy and noninvasive imaging analyses. Although the magnitude tends to be smaller, retinol induces similar changes in skin histology, and gene and protein expression as compared to retinoic acid application." (Kong et al.Journal of Cosmetic Dermatology, Vol.15, Issue 1, p. 49-57) Dra. Miriam's advice: Because of the greater improvement in epidermal thickness and collagen synthesis, I would choose retinoic acid over retinol (if your skin can tolerate it). Otherwise, start with retinol, gradually escalating to retinoic acid 0.05% then 0.1%.