RecruitingPhase 1Drug trialAn Open-Label, Two-Cohort, Pharmacokinetic Study in a Maximal Use Setting for Patients With Actinic Keratosis on the Upper Extremities or the FaceThe research study will evaluate how the body absorbs and reacts to reformulated Levulan Kerastick when applied to actinic keratosis lesions (AKs) on the skin of the forearms or face followed by photodynamic therapy (PDT), a treatment that uses application of blue light.