Here's why:
* Toner is not a dye: Toner is a semi-permanent color that deposits color onto the hair shaft but does not penetrate it like permanent dye. It fades gradually with washing.
* Developer is a chemical activator: Developer is a chemical that helps lift the hair cuticle and allows color molecules to penetrate.
* Mixing them is dangerous: Using toner with developer can cause severe damage to your hair. The developer will lift the cuticle and allow the toner to penetrate deeper than intended, resulting in unpredictable color changes, severe dryness, breakage, and even chemical burns.
What to do instead:
* Follow the instructions: Always follow the manufacturer's instructions for both the toner and developer.
* Use a developer specifically designed for toner: Some toners come with a developer specifically formulated to work with them. If you're unsure, consult a professional hairdresser.
If you're looking to change your hair color, it's always best to consult a professional hairstylist. They can assess your hair type, desired color, and recommend the best products and techniques to achieve your desired results safely.