Retinaldehyde (retinal) is a form of vitamin A used in skin creams. It is the natural precursor of retinoic acid, the active form in prescription tretinoin: skin cells turn it into retinoic acid and into stored forms of vitamin A.
Also known as: retinal, RAL, retinaldehyde cream.
Creams are labeled by percent. One trial used 0.05% and 0.1% retinaldehyde creams twice a day for 3 months (Kwon 2018). These are study protocols, not a recommendation.
How it works: skin cells take up retinaldehyde and convert it into retinoic acid; in living models most of it was stored as retinyl esters, which deliver relatively small amounts of retinoic acid from a large reserve (Sorg 1999).
What studies show: in 40 Korean women using 0.1% or 0.05% retinaldehyde cream twice a day for 3 months, 95% in each group improved overall; skin texture improved by 13.7% and 12.6%, water loss fell and moisture rose, with no difference between strengths, and only the 0.1% cream lowered the melanin (pigment) index. Both were well tolerated (Kwon 2018). That trial compared two strengths and had no placebo group.
Tolerance: a 1999 review, including 45 people who used it on the face for 12 to 89 months, reported that retinaldehyde was much better tolerated than retinoic acid, was not phototoxic and caused no side effects with long-term use (Sachsenberg-Studer 1999). For the prescription retinoid, see tretinoin.
We found no published half-life or time to peak for retinaldehyde put on the skin, so we do not list one.
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