I have previously coloured my hair with a chemical dye. Can I use basma over it? — Cosmetic basma Indian clay 25 g Fitokosmetik

It is generally advised to avoid applying plant dyes like basma over hair that has recently been treated with synthetic colourants, perms, or strong lighteners. The interaction between the different types of colourants can be unpredictable and may result in patchy, uneven colour or unexpected tones.

The pigments in basma wrap around the hair's outer cuticle, while many chemical dyes are designed to penetrate the hair shaft and alter its internal structure. These different mechanisms can conflict. For best results, allow your hair to grow out significantly, or wait for the chemically treated portion to be trimmed away, before switching to plant-based colour.

If you wish to proceed, a comprehensive strand test is non-negotiable. Apply your planned basma-henna mixture to a small, hidden section of hair that includes both your natural regrowth and the chemically treated lengths. Observe the result over the full 48-hour oxidation period. This will show you how the colours develop differently on each section and help you decide if the final look is acceptable.