Hello, if it is pure white, just dilute some bleach and soak it for 10 minutes, then wash it and dry it.

If there are patterns, I suggest you spray some collars on the yellow part of the white background. 10 minutes later, brush with a brush, and dip some bleach in the particularly yellow part. Then add washing powder, scrub and dry.

If the hair is oily, it is recommended to buy a pillow towel or use a pillowcase full of patterns (never use white). Wash pillowcases every 1 month.