Study population: 15 healthy volunteers ≥18 years, who give written informed consent Intervention: In each subject, four test regions on subject's back of 1x1 cm will be randomly allocated to (I) pretreatment with the fractional CO2 laser at 5% density, (II) pretreatment with the fractional CO2 laser at 15% density, (III) pretreatment with the fractional Er:YAG laser at 5% density and (IV) pretreatment with the fractional Er:YAG laser at 15% density. After pretreatment, articaine hydrochloride 40 mg/ml + epinephrine 10 μg/ml 30 solution (AHES) will be applied on the test regions with 15 minutes occlusion time. After 15 minutes a pain stimulus, consisting of a pass with the fractional CO2 laser at 50 mJ and 5% density (scanned area 6x6 mm), will be given at each test region. In addition, a reference pain stimulus with the CO2 laser at the same settings will be given at unanesthetized skin. Subjects will be asked to indicate pain on a visual analogue scale (VAS) from 0-10 (0: no pain; 10: worst imaginable pain) directly after each pain stimulus.