Changes in human skin after topical PDT with hexyl aminolevulinate.

Background: Photodynamic therapy (PDT) induces physiological changes in human skin, but details and kinetics are not known.

Methods: Changes in human skin induced by PDT with red light in the presence of topically applied cream with the hexyl aminolevulinate (HAL) were investigated in the skin of five healthy volunteers. In addition to testing the effects of HAL-PDT three control studies were performed on the volunteers: (A) the HAL containing cream was applied to the skin without light exposure; (B) the cream without HAL was applied to the skin; (C) the skin was exposed to light in the absence of the cream.