When it comes to dyeing your hair, whether you should wash it beforehand depends on several factors, including your hair type, the type of dye being used and your scalp’s condition. 

When you should wash:

– If your hair is oily or product-laden: washing your hair 24-48 hours before dyeing can remove excess oil and styling products that may block the dye from penetrating evenly.

– If you’re using semi-permanent dye: clean hair helps this type of dye adhere better, as it doesn’t contain strong chemicals that can strip oils.

When you shouldn’t wash:

– If your scalp is sensitive: washing your hair strips away natural oils that protect your scalp during the dyeing process, so it’s best to avoid washing it right before dyeing, especially if you have sensitive skin.

– When using permanent or bleach-based dyes: These dyes contain strong chemicals, so unwashed hair with natural oils provides a protective barrier for your scalp, reducing irritation.

General guidelines:

– Ideally, wash your hair 24-48 hours before your dye appointment to remove dirt and excess oil while allowing your scalp to build up a bit of natural protection. 

– Avoid using conditioner, as it can create a barrier that prevents the dye from fully absorbing.

By considering these factors, you can achieve a more even and vibrant hair color while minimizing potential scalp irritation.