What is methylene red?

Methylene red is a synthetic dye commonly used in histochemistry to stain biological samples. It is also used as an indicator in various chemical reactions, including the detection of reducing agents. The dye appears as a dark red or brown powder and is soluble in water. Methylene red binds to basic components of cellular material such as nucleic acids and proteins, which allows it to be used to visualize cell structures under a microscope. It has also been used as a photosensitizer in photodynamic therapy to treat certain types of cancer. However, excessive exposure to methylene red can cause skin irritation and eye damage.