Dyed hair -- be picky with your shampoo!
Most of the off the shelf shampoo are not good for dyed hair
The cuticle of coloured hair is normally “pulled opened” through the dying and perm processes, making the hair weak and prone to dryness. Dyed colour may also be washed away easily as the cuticle is “opened”.
Shampoo for coloured hair needs to achieve two objectives:
minimize colour loss during the washing process i.e. “colour safe”
prevent further damage and preserve the weakened hair strand
The choice of shampoo need to be ultra mild in order not to wash away the hair dye. It also need to be pH adjusted to at least 5.5 or below in order to help close up the cuticle to minimize colour loss and preserve moisture in the hair. After shampoo, then must use conditioner to coat the hair strand to preserve the opened cuticle.
洗髮水需要非常溫和，以免洗掉染髮劑。還需要將其 pH 值調整到至少 5.5 或更低，以幫助閉合角質層，以最大限度地減少顏色損失並保持頭髮中的水分。洗髮後，必須使用護髮素塗抹在髮絲上，以保護打開的角質層。