One word: COTTON! 100%!
The brand I use is called Sugar N Cream by Lily. Lionbrand yarn also has one that's 100% cotton. Sometimes I've seen yarn marked 'Kitchen cotton', which sounds like it would be good. These types of yarn often get softer when they're washed, which would be good for face clothes.
Just make sure you can throw it in the washer and dryer.
HAPPY :XX: :XX: :XX: