Abstract: Methods, devices and composition are disclosed for treating oral, skin and nail diseases, including inflammatory periodontal disease, onychomycosis and dermatophytosis. In a preferred embodiment a method for treating oral, skin and nail infections comprises administering a photosensitizing compound in long term effect or timed release formulations, including local highly concentrated formulations, and activating the photosensitizer with radiation to selectively destroy bacteria, fungi and other microbial bodies. In another preferred embodiment, photosensitizers are housed within nanoparticles, and can be gradually released through biodegradation or periodically released by such processes as brushing, irradiation and chemically induced release. The diffusion speed of the photosensitizers can be accelerated by brushing. In another embodiment, the photosensitizer molecule is also modified to more effectively target the molecule to the unwanted oral bacterial and fungal species.