This clinical trial serves the purpose to compare the long-term effects of a treatment of actinic keratosis - your skin disorder - using Aldara® 5% cream (Imiquimod) or Solaraze® 3% gel (Diclofenac) on the face or the scalp. In particular, it should be found out whether the healing effect of these two medications on the skin lesions (i.e. the damaged skin parts) can be maintained for a prolonged period.