Permanent hair dye:
* Opened bottle: Up to 6 months if stored properly (see below)
* Unopened bottle: Up to 2-3 years if stored properly
Semi-permanent and temporary hair dye:
* Opened bottle: Up to 3-6 months if stored properly
* Unopened bottle: Up to 1-2 years if stored properly
How to store hair dye for optimal shelf life:
* Keep the dye in its original bottle.
* Store in a cool, dark, and dry place. Avoid direct sunlight and heat.
* Keep the bottle tightly closed. This prevents air from entering and oxidizing the dye.
* Check the expiration date. Most hair dye bottles have an expiration date printed on them.
Signs that hair dye has gone bad:
* Color change: The dye may become darker or lighter.
* Consistency change: The dye may become thicker or thinner.
* Unpleasant smell: The dye may have a strong, chemical odor.
* Separation: The dye may separate into layers.
Important note: It's always better to err on the side of caution and use fresh hair dye. If you're unsure about the quality of your dye, it's best to discard it and purchase a new bottle.