Asha Patel Shah, MD, MBA, FAAD, a board-certified dermatologist, adjunct assistant professor of dermatology at Emory University, and head of Medical Affairs North America, Skin Health & Beauty at Kenvue, discussed her team’s recent research on retinol and retinoid bioactivity when layered with moisturizers highlighted in a poster at the 2025 American Academy of Dermatology (AAD) Annual Meeting held March 7-11 in Orlando, Florida.

The poster, titled “Tretinoin and Retinol Bioactivity are Retained When Layered With Adjunctive Water Gel Moisturizer or A Water Cream Moisturizer in an ‘Open Sandwich’ Regimen” evaluated the impact of different moisturizer layering techniques on the bioactivity of retinol and tretinoin creams, which was measured by gene expression.

“Open sandwich” moisturization, by applying a lightweight water gel moisturizer before applying retinol OR applying water cream moisturizer after retinol, preserves the retinoid bioactivity compared to the “full sandwich” method of moisturizer-retinol-moisturizer. The full sandwich method reduced retinoid bioactivity by approximately threefold.

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