The purpose of this study is to investigate the efficacy of LAS41005 in comparison to placebo and to LAS106521 in actinic keratosis (AK).

To investigate as primary objective:

• Superiority to placebo and non-inferiority to LAS106521 measured by histological clearance of one predefined target lesion;

To investigate as secondary objective:

• Superiority to LAS106521
• Improvement of treated lesions (lesion response)
• Assessment of tolerability and safety by physicians global assessment score (PGA, PGT)
• Patient's assessment of tolerability and efficacy and patient's compliance

Main Inclusion Criteria:

• Have at least 4 but not more than 10 clinically confirmed AK target lesions of mild to moderate intensity within the face/forehead or bald scalp (excluding eyelids, lips, and mucosa), i.e. actinic keratosis grade I and II according to Olsen EA et al. 1991
• Woman of childbearing potential are allowed to participate in this study only if they use a highly effective method of contraception

Main Exclusion Criteria:

• Have received effective treatment of AK in the three months preceding this clinical trial
• Have known hypersensitivity to LAS41005 or LAS106521
• Have currently other malignant or benign tumors of the skin within the treatment area (e.g. malignant melanoma, basal cell carcinoma, squamous cell carcinoma)
• Patient's taking phenytoin
• Show cornu cutaneum like alterations of the skin in the face or the bald scalp (target area)