Neutral red is a hydrochloride obtained by combining the free base of neutral red with one equivalent of hydrochloric acid. Neutral red acts as a pH indicator, changing from red to yellow between pH 6.8 and 8.0. It has a role as a dye, an acid-base indicator and a two-colour indicator.
Neutral red is a eurhodin dye used for staining in histology. It stains lysosomes red. It is used as a general stain in histology, as a counterstain in combination with other dyes, for many staining methods. Together with Janus Green B, it is used to stain embryonal tissues and supravital staining of blood.
Neutral red is especially recommended for initial evaluation of blood .