DAB (tetrahydrochloride hydrate) is commonly utilized as a chromogenic substrate in immunohistochemistry and enzyme histochemistry to reveal specific antigens or enzymes. Upon oxidation by hydrogen peroxide, DAB (tetrahydrochloride hydrate) forms a brown precipitate at the location of the antigen or enzyme, facilitating microscopic detection and observation. Additionally, DAB (tetrahydrochloride hydrate) holds potential applications in various research fields, such as the development of biosensors and the study of cellular oxidative stress.