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

Tretinoin 0.1% and 0.025% produce similar clinical and histologic changes in patients with photoaging, despite significantly greater incidence of irritation with the higher concentration. The separation between clinical improvement and irritation suggests that mechanisms other than irritation dominate tretinoin-induced repair of photoaging in humans.