Here's why:
* Semi-Permanent Hair Color: Deposits color only on the outer layer of the hair shaft. It doesn't contain ammonia or peroxide (developer) to open the hair cuticle. It gradually fades with each wash.
* Developer (Hydrogen Peroxide): Used with permanent and demi-permanent hair color. It opens the hair cuticle, allowing the color to penetrate and change the hair's underlying pigment.
What happens if you mix developer with semi-permanent color?
* Unpredictable Results: The color outcome will be unpredictable and likely not what you intended.
* Damage to Hair: Developer can damage your hair if it's not used correctly or when it's mixed with products it's not designed for. Semi-permanent color is meant to be gentle, and adding developer can defeat that purpose.
* Potential for Uneven Color: Because the semi-permanent formula isn't meant to be lifted into the hair shaft, adding developer may create uneven or blotchy results.
In short, mixing developer with semi-permanent hair color is not recommended and can lead to unwanted results and potential hair damage.
Always follow the instructions provided with your hair color product. If you're looking to lighten your hair, you'll need a different product altogether, like bleach, which is designed to be used with a developer.