I love the pillow but,
The great pillow cases collects body oils from your head and it does not wash out.
When I wash them, they still stay stained.
I take showers everyday so it's not a " I'm dirty" problem.
It is definitely the material of the pillow cases.
Also,
I recommend white ones instead of colored pillow cases so you can't see stains after they are washed so your bed looks clean when you make it
I change out my pillow cases constantly.
I will not purchase anymore of these pillow cases ...