Thanks to the Kiehl's Retinol Serum, I am now a believer in retinol's anti-ageing effects. Because I didn't experience any discomfort, I can confidently say that it was a nice introduction to retinoids. The product does have a hefty price point. However, you're paying for the gentle, precise formulation as well as the glass packaging. If you're willing to treat yourself, this is a good option.