The Best How Long After Mixing Hair Dye Can You Use It References. Web when you mix permanent dye with peroxide, you should plan to use it within thirty minutes. Your hair dye needs to get into a chemical.
Unopened hair dye has a shelf life of three years, but once it is exposed to air, the oxidation process occurs. According to the cleveland clinic, you should never mix different. After about 30 minutes elapse, your permanent hair dye won’t be entirely.
