Laser therapy aims to prevent run-of-the-mill "zits" (papules and pustules), and appears to be less effective with non-inflammatory acne (whiteheads and blackheads) and severe lesions (cysts and nodules). Lasers is light devices, work on the premise of exciting compounds called porphyrins, which live inside acne bacteria. When the lasers excite the porphyrins, the porphyrins damage the bacteria wall, effectively killing the bacteria. Less acne bacteria should help reduce symptoms of acne. Laser treatment may also reduce sebum (skin oil) levels.