A drug used to treat actinic keratosis (a skin condition that may become cancer). The drug is also being studied in the treatment of squamous cell and basal cell skin cancers and other types of cancer. When aminolevulinic acid hydrochloride is taken up by cells, including cancer cells, and then exposed to certain types of light, it becomes active and kills the cells. It is a type of photosensitizing agent. Also called Levulan and Levulan Kerastick. OR A topically administered metabolic precursor of protoporphyrin IX. After topical administration, aminolevulinic acid hydrochloride (ALA HCl) is converted to protoporphyrin IX (PpIX) which is a photosensitizer. When the proper wavelength of light activates protoporphyrin IX, singlet oxygen is produced, resulting in a local cytotoxic effect.