Metvix PDT Versus Vehicle PDT With Aktilite CL128 Lamp in Patients With Actinic Keratosis on the Face and Scalp

Inclusion Criteria: * Clinical diagnosis of 4-10 previously untreated, not pigmented, non-hyperkeratotic AK lesions of 3 mm or more diameter of Grade 1 and/or 2 of the face and/or scalp where other therapies are unacceptable or considered medically less appropriate. * Males or females above 18 years of age. * Written informed consent. Exclusion Criteria: * Participants with porphyria. * Participants immunosuppressed for idiopathic, disease specific or therapeutic reasons. * Known allergy to MAL, a similar PDT compound or excipients of the cream. * Participants with history of hypersensitivity to nut products or other known protein antigens. * Participation in other clinical studies either currently or within the last 30 days. * Participants receiving local treatment (including cryotherapy and curretage) in face / scalp area within the last 30 days. * Participants receiving topical treatment (including imiquimod, 5-FU and diclofenac) in face / scalp area within the last 3 months. * Pregnant or breast-feeding: All women of child-bearing potential must use adequate contraception (oral contraceptives, intrauterine device, contraceptive skin patch, etc) during the treatment period and one month thereafter. In addition, they must have a negative pregnancy test prior to treatment. * Any conditions that may be associated with a risk of poor protocol compliance. * Participants currently receiving regular ultraviolet radiation therapy.