Photosensitizers are compounds that absorb specific wavelengths of light, converting light energy into chemical energy, widely used in photodynamic therapy. They have diverse structures, including porphyrins and chloroaluminum phthalocyanine, and can localize in various cellular components like mitochondria and membranes. Photosensitizers induce cell death by generating reactive oxygen species involved in oxidative stress responses. Their effectiveness is influenced by light intensity, wavelength, and the cellular environment. Differences and mutations in gene expression can affect the absorption and activity of photosensitizers, thereby impacting therapeutic outcomes.