Retinol (Vitamin A)

Retinol remains the most evidence-backed anti-aging ingredient available over the counter, outperforming #2 Niacinamide in collagen-stimulation studies. Decades of clinical trials confirm it accelerates cell turnover by up to 30%, reduces fine lines by 27% over 12 weeks, and fades hyperpigmentation significantly more than typical antioxidants. Prescription tretinoin (retinoic acid) is the gold standard, but over-the-counter retinol esters offer a gentle entry point for sensitive skin types.