How do you get mascara stains out of towels?

First, rinse it out the best you can in the sink. Use an enzyme treatment such as Shout. Soak the area with the treatment, rub it in a little, and let it sit for a couple of hours. Go ahead and wash it as usual. If there is any stain remaining after the wash, do it again. Do not put it in the dryer until the stain is gone. The dryer will set the stain making it difficult to impossible to remove.