Aminolevulinic Acid-photodynamic Therapy for Facial Actinic Keratosis Treatment and Prevention

Inclusion Criteria: 1. Clinical diagnosed with AK (OLSEN classification grade I, II, III), aged \> 18 years (Because no dosing or adverse event data are currently available on the use of topical aminolevulinic acid in patients \<18 years of age, children are excluded from this study); 2. All patients are unfit and reluctant to undergo surgery for any reasons, and volunteered to participate in the study and ability to understand and the willingness to sign a written informed consent. Patents are willing to pay for the treatment, and agreed to take a picture of the skin lesions. Exclusion Criteria: 1. Those who had ALA-PDT and any other studies that affect this study within 12 weeks ; 2. There are other facial diseases that may affect the efficacy evaluation, such as other photodermatosis; 3. Take phototoxic or photosensitizer within 8 weeks; 4. Clinical and / or pathological prove that the tumor has invaded other organs or tissues; 5. Serious immunocompromised persons; 6. scar constitution; 7. Patients are known to have skin photosensitivity, porphyria, or allergies to ALA, light or lidocaine; 8. Persons are suffering from severe internal diseases, mental and mental illness, infectious diseases or pregnant or lactating women.