Auramine O is primarily used as a fluorescent dye in various biological and industrial applications. In microbiology, it is employed as a staining agent to detect acid-fast bacteria, such as Mycobacterium tuberculosis, under a fluorescence microscope. This makes it a valuable tool in medical diagnostics for identifying tuberculosis infections. Additionally, Auramine O is utilized in the textile industry for dyeing materials like synthetic fibers (e.g., polyester, nylon, acrylic), paper, leather, silk, and plastics, providing a bright yellow color that is durable and visually appealing. It is also used in the manufacturing of certain types of inks and as a component in some chemical indicators. However, due to its potential toxicity and carcinogenic properties, its use is regulated, and safety precautions are essential during handling.