Benzidine is primarily used in the production of azo dyes and pigments. These dyes are applied in the textile, paper, and leather industries to color fabrics and materials. It has also been used in the development of certain chemical reagents for analytical testing, such as in tests for blood due to its color-changing properties when exposed to hemoglobin. However, due to its high toxicity and carcinogenic nature, its use has been heavily restricted or discontinued in many countries. Where still in use, it is handled under strict industrial safety controls.