Aminolevulinic acid causes skin cells to become much more sensitive to certain types of light. Skin cells treated with aminolevulinic acid and exposed to a special light die and then slough off. Aminolevulinic acid is used to treat warty overgrowths of skin (actinic keratoses) on sun-exposed areas of the face and scalp. Treatment involves application of aminolevulinic acid, followed 14 to 18 hours later by exposure to a special blue light. Aminolevulinic acid may also be used for purposes other than those listed in this medication guide.