This is a randomized clinical trial evaluating blue light 5-aminolevulinic acid (ALA) photodynamic therapy with different incubation times for the treatment of actinic keratosis.

Subjects who are interested in participating, currently living in the Chicago metropolitan area, and meet inclusion and exclusion criteria will be enrolled in the study. Subjects will be randomized to either 1) zero time ALA incubation or 2) 1 hour ALA incubation. Demographic and health data will be collected prior to treatment initiation. Three visits will be conducted: screening, treatment, and follow up visit at 8 weeks.

This study is a pilot study designed to determine feasibility of this procedure.

Inclusion Criteria:

1. Subjects who have been diagnosed with actinic keratosis.
2. Subjects who by the investigator deem to be suitable for photodynamic therapy of the face or scalp.
3. Males or females ≥ 18 years old
4. Fitzpatrick skin types I-VI
5. Subjects are in good health as judged by the investigator.
6. Subjects who are willing and have the ability to understand and provide informed consent for participation in the study and are able to communicate with the investigator.

Exclusion criteria:

1. Subjects who by the investigator are not suitable for photodynamic therapy.
2. Lesions suspicious or proven for skin cancer
3. History of 2 or more ALA- PDT treatments within the past 6 months.
4. Use of keratolytics within 2 days of initiation of treatment (e.g., >5% urea, glycolic acid, lactic acid, salicyclic acid)
5. Cryotherapy within the past 2 weeks.
6. Topical retinoids within the past 4 weeks
7. Procedures, such as microdermabrasion, ablative lasers, ALA-PDT, chemical peels, 5-fluorouraci, diclofenac, imiquimod within the past 8 weeks
8. Systemic retinoids within the past 6 months
9. Pregnant or breast feeding
10. Uncooperative subjects or subjects with neurological disorders who are incapable of following directions or who are predictably unwilling to return for follow-up examinations.
11. Subjects who are unable to understand the protocol or give informed consent.
12. Subjects who in the opinion of the investigator are not suitable for the study.