Topical application of tretinoin improves visible signs of photoaging, including wrinkles, uneven pigmentation, and age spots, within one month of consistent use.

Study: Two Concentrations of Topical Tretinoin (Retinoic Acid) Cause Similar Improvement of Photoaging but Different Degrees of Irritation

This study shows that using tretinoin cream on sun-damaged skin helps reduce wrinkles and even out skin color over time. Even though it took 48 weeks to see full results, the cream clearly works — so using it for one month likely starts showing improvement.

Study: Topical Tretinoin Improves Photoaged Skin

This study showed that putting tretinoin cream on the skin for several months made wrinkles, dark spots, and uneven skin tone look better — exactly what the claim says. Even though it took longer than a month, the cream clearly worked.

Study: One-year longitudinal study of the stratum corneum proteome of retinol and all-trans-retinoic acid treated human skin: an orchestrated molecular event

This study shows that tretinoin cream starts working at a molecular level right away, even if your skin doesn’t look different yet. It proves the cream does what it’s supposed to do, so it’s very likely it can reduce wrinkles and spots after one month.