Review Of How Long To Keep On Hair Dye References. The hair dye needs 30 minutes for the ammonia and peroxide to work their way into the hair cuticle to change the hair’s natural pigment. Avoid sulfates and harsh chemicals.

Web the short answer. Expired hair dye can cause the color to turn out wrong or even cause an allergic reaction. Web hair dye or color must stay on your hair for an exact amount of time to penetrate the hair.