Efficacy and Safety Study of LAS41007 in the Treatment of Actinic Keratosis

Inclusion Criteria: * At least 4-10 clinically assessed actinic keratosis grade I to II (according to Olsen et al, 1991) in the face/forehead and/or on the bald scalp * The diameter of each AK target lesion is not less than 0.5 cm and not greater than 1.5 cm * The target lesions must be located in overall 2 treatment areas with a size of 25 cm2 per treatment area Exclusion Criteria: * Have evidence of clinically significant or unstable medical conditions such as: * metastatic tumor or tumor with high probability of metastatic spread * heart failure (NYHA class III or higher) * immunosuppressive disorder (e.g. HIV) * hematologic, hepatic, renal, neurologic or endocrine disorder. * collagen-vascular disorder (e.g. cerebrovascular disorder or other bleedings). * gastrointestinal disorder (e.g. active ulcera or history of recurrent peptic ulcera or hemorrhage) * Suffer from paresthesia in the treatment areas * Show Cornu cutaneum of the skin and/or hypertrophic AK lesions in the treatment areas