Soft cloth rag
Take a soft cloth (a towel is ok), wet it a little, and gently wipe the doll. You will find that the stain is slowly fading.
Give it a little shave.
If the stain still exists, try scraping the cloth gently with your nails. The rubber of the doll's head is very thick, so don't worry about scratching. But remember, don't be too sharp, or both the doll and you will get hurt? .
Soap water wiping
If it is a stain of paint or pen and ink, just change the water into soapy water. A spoonful of water and a drop of shower gel will do! Similarly, gently wipe with a cloth, and then wipe with a clean wet cloth.
Clean wet cloth
Be sure to use a "clean wet cloth" so that the doll's face will be as bright as new!