The present study aimed to evaluate the acute locally injurious property of hydroxyl radical generation system by photolysis of H(2)O(2), which is a new disinfection system for the treatment of periodontitis developed in our laboratory. Firstly, generation of the hydroxyl radical by a test device utilizing the photolysis of H(2)O(2) was confirmed by applying an electron spin resonance (ESR)-spin trapping technique. Secondly, the bactericidal effect of the device was examined under a simulant condition in which Staphylococcus aureus suspended in 1 M H(2)O(2) was irradiated with laser light emitted from the test device, resulting in substantial reduction of the colony forming unit of the bacteria within a short time as 2 min. Finally, acute topical effect of the disinfection system on rat oral mucosa and wounded skin was evaluated by histological examination. No abnormal findings were observed in the buccal mucosal region treated three times with 1 M H(2)O(2) and irradiation. Similarly, no abnormal findings were observed during the healing of skin treated with 1 M H(2)O(2) and irradiation immediately after wounding. Since topical treatment with the novel disinfection technique utilizing the photolysis of H(2)O(2) had no detrimental effect on the oral mucosa and the healing of full thickness skin wounds in rats, it is expected that the acute locally injurious property of the disinfection technique is low.