Dansyl amide is a reactive fluorescent dye that is used in biochemistry and chemistry to label substances with the fluorescent dansyl group. It is also produced as a side-product in the labelling of amino acids with dansyl chloride. Dansyl amide is a reactive fluorescent dye that is used in biochemistry and chemistry to label substances with the fluorescent dansyl group. It is also produced as a side-product in the labelling of amino acids with dansyl chloride.