Photodynamic therapy (PDT) is a therapeutic modality for cancer and various non-malignant diseases, including infections, which uses an interaction of light with photosensitizers (PS) and photoactivation using a specific wavelength of light in the presence of molecules. The PS agent is first administered to the patient, either orally or topically, and is then absorbed by the abnormal cells. Photosensitizers are non-toxic dyes that are activated by the absorption of visible light to initially form the excited singlet state, followed by the transition to the long-lived excited triplet state generating cytotoxic reactive oxygen species (ROS), thus inducing apoptosis, necrosis, and autophagy of the cells. PDT has been approved as a non-invasive option for the treatment of anti-tumors and other diseases, such as lung, esophageal, and bladder cancer.