Indigo carmine is widely used as a dye in various medical and diagnostic applications. In medicine, it is commonly employed as a staining agent during surgical procedures, particularly in urology and gynecology, to help visualize structures like the urinary tract or to identify leaks in the bladder. It is also used in diagnostic tests, such as the Schirmer test, to assess tear production in ophthalmology. Additionally, indigo carmine serves as a pH indicator in laboratory settings, changing color in response to acidity or alkalinity. Its vibrant blue color makes it useful in microscopy and histology for staining tissues and cells. In some cases, it is utilized in food and textile industries as a coloring agent, though its primary applications remain in the medical field.