Methylene Blue (Methyltioninium Chloride) – Medicine, Science, and Industry Methylene Blue is a dark blue, water-soluble crystal with antioxidant, antimicrobial, and neuroprotective properties. It is used in medicine to treat methemoglobinemia, urinary tract infections, and malaria; in biochemistry and microscopy as a dye and redox indicator; and in industry for dyeing textiles and paper. Ideal for laboratory research, collecting, and industrial applications.