If stored properly and never opened, hair-dyes do not expire. However, they do go bad if they have been opened, used and not stored properly. 

The average shelf life of an opened hair dye is around 1-2 years.

What Causes Hair-Dyes To Go Bad?

If left opened, air and moisture can cause oxidation in the dye. Micro-organisms may spoil the dye by thriving in the ammonia rich environment.

What Does Expired Hair Dye Look Like?

Expired hair dye have the following characteristics:

1. Water-like Liquid –  A thin layer of water-like liquid forms on the top of the dye. This means the chemicals inside the dye have spoiled.
2. Bad Odor – The dye lets out a bad odor which is caused the micro-organisms thriving in it.
3. Change in Color – You may notice that the color of the dye faded.