Auramine O is primarily used as a fluorescent dye in various biological and industrial applications. In microbiology, it is widely employed as a staining agent for the detection of acid-fast bacteria, such as Mycobacterium tuberculosis, in sputum samples. The dye binds to the mycolic acid in the bacterial cell walls, allowing for visualization under a fluorescence microscope. Additionally, Auramine O is utilized in histology for staining tissues to highlight specific cellular structures. In the textile industry, it serves as a dye for coloring fabrics, particularly in producing bright yellow shades. It is also used in the paper industry for coloring paper products. However, due to its potential toxicity and carcinogenic properties, its use is regulated, and safer alternatives are often sought in certain applications.