Where Kiehl's Retinol Skin-Renewing Daily Micro-Dose Serum really shines is hydration efficacy, scoring 9.6 compared to Su:m37 Secret Essence's 5.5. With Glycerin, Butylene Glycol, and Pentylene Glycol in its top ingredients, Kiehl's Retinol Skin-Renewing Daily Micro-Dose Serum delivers stronger moisture-binding capability.
Active Ingredient Strength is another area of separation. Kiehl's Retinol Skin-Renewing Daily Micro-Dose Serum scores 7.8 here versus 4.2 for Su:m37 Secret Essence. That difference comes down to how each formula is built — the ingredient list tells the story.
Kiehl's Retinol Skin-Renewing Daily Micro-Dose Serum brings Niacinamide, Acetyl Dipeptide-1 Cetyl Ester, and Adenosine as actives, while su:m37 Secret Essence relies on Niacinamide, Adenosine, and Tocopherol. Both approaches have merit, but the positioning and supporting ingredients make the difference.
At premium pricing with a score of 9.0, Kiehl's Retinol Skin-Renewing Daily Micro-Dose Serum delivers strong value. Su:m37 Secret Essence sits at the luxury level with a 6.7 score — the extra cost doesn't translate to better scores here.