Retinaldehyde

A vitamin A aldehyde that sits one metabolic step closer to retinoic acid than retinol, making it more potent at lower concentrations while remaining available without a prescription. Converts to retinoic acid in the skin more efficiently than retinol, producing comparable anti-aging and anti-acne effects with less irritation than prescription tretinoin. Human clinical trials show improvements in fine lines, skin texture, and acne comparable to lower-dose tretinoin. Effective at 0.05–0.1%; irritation is still possible and a slow introduction is recommended. Significantly more effective than retinol on a weight-for-weight basis, but less widely formulated due to stability challenges.