Topical treatment of mild to moderate actinic keratosis located on the face and head with Solaraze® is known to be a safe and efficient treatment option. However, it is unclear if an expansion of the treatment period to 6 months will increase the rate of complete responses.

Therefore the investigators will evaluate the efficacy and safety of the treatment of actinic keratosis with Solaraze® applied twice daily to the face and head over 3 or 6 months of treatment.

Inclusion Criteria:

• Visible and histologically proven actinic keratosis
• Prepared and able to give written informed consent
• ≥ 18 -80 years of age
• Prepared and comply with all study requirements, including the following: application of gel on the treatment area twice a day, 5 / 7 clinic visits during the prestudy, treatment, posttreatment, and follow-up period
• Pre- and posttreatment biopsy for histological confirmation (of clearance) of actinic keratosis diagnosis

Exclusion Criteria:

• Data of clinically significant, unstable, cardiovascular or haematologic, hepatic, neurologic, renal, endocrine, collagen-vascular, or gastrointestinal abnormalities or diseases
• Known allergies to any excipient in the study drug
• Any dermatological disease and/or condition in the treatment or surrounding area (3 cm distances from treatment area) that may be exacerbated by treatment with diclofenac or cause difficulty with examination
• Active chemical dependency or alcoholism, as assessed by the investigator
• Currently participating in another clinical study or have completed another clinical study with an investigational drug within the past 30 days
• Received topical treatment at the treatment area with imiquimod or 5-FU within a time period of 1 month
• Invasive tumours within the treatment area, e.g. merkel cell carcinoma, squamous cell carcinoma, basal cell carcinoma, the latter is accepted if completely surgically removed