For people with actinic keratosis, cumulative skin damage is caused by repeated exposure to all ultraviolet light, including that found in sunshine. Over the years, the genetic material of cells becomes irreparably damaged and produces lesions. The lesions, like those seen here on the arm, may later become cancerous.
Review Date 11/10/2020
Updated by: Ramin Fathi, MD, FAAD, Director, Phoenix Surgical Dermatology Group, Phoenix, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.