A combination of retinaldehyde (a gentler retinoid precursor) and glycolic acid showed promise for treating both acne and the dark marks it leaves behind (PIH). The combo appeared to work better than either ingredient alone, with users reporting good tolerance—meaning less irritation than other acne treatments.

This was a review of preclinical and clinical trial data on a specific product combining 0.1% retinaldehyde with 6% glycolic acid, examining its effects on acne and post-inflammatory hyperpigmentation.

Funding not disclosed in abstract