A process of performing photodynamic therapy is provided along with a photosensitizer composition suitable for the process. The photosensitizer composition comprises at least one photoactive ingredient in a chemically reduced state. According to the process, the photosensitizer composition having at least one photoactive ingredient in a chemically reduced state is provided. The photosensitizer composition is applied to tissue or other substrate such that the at least one photoactive ingredient is at or travels to a location adjacent a target medium and the at least one photoactive ingredient is then altered to a photoactive state. The at least one photoactive ingredient is then exposed to light energy for assisting in inhibiting at least one pathogen at the target medium.