Phloxine B is primarily used as a biological stain in microscopy to enhance the visibility of cellular components. It is particularly effective in staining plant tissues, helping researchers distinguish between different cell structures under a microscope. Additionally, it is utilized in entomology for marking and tracking insects, as its bright color allows for easy identification. In the food industry, Phloxine B serves as a color additive, though its use is regulated and limited due to safety concerns. It is also employed in some cosmetic products for its vibrant red hue. Furthermore, Phloxine B has been explored for its potential in photodynamic therapy, where it can act as a photosensitizer to target and destroy certain types of cells when exposed to light.