5-Aminolevulinic acid hydrochloride is widely used in photodynamic therapy (PDT) for the treatment of various skin conditions, including actinic keratosis and certain types of skin cancer. It acts as a precursor to protoporphyrin IX, a photosensitizing agent that accumulates in abnormal cells. When exposed to a specific wavelength of light, it generates reactive oxygen species that selectively destroy targeted cells.

In dermatology, it is applied topically to the affected area, allowing for precise treatment with minimal damage to surrounding healthy tissue. It is also being explored for use in diagnosing bladder cancer, where it helps visualize malignant cells during cystoscopy by causing them to fluoresce under blue light. Additionally, research is ongoing into its potential applications in treating other cancers and microbial infections, leveraging its ability to induce targeted cell death.