Doesn't this tip just make you want to say "Duh! Why didn't I think of that already?"
If you get as much sleep as you need, you're spending at least seven hours each night with your face on that pillow. And even if you wash your face before going to bed (and you should – gently, always gently!) your pillowcase will slowly pick up oil, sweat, bacteria and dead cells from your skin, as well as dirt and dust and maybe allergens from the air.
Sleep clean! Change your pillowcase for a clean one every two to three days.
You can get a silk pillowcase on sale on Amazon for about $10. If you owe yourself a present, splurge and buy a few. Silk and satin are gentle fabrics for your skin.
In addition to being comfy to sleep on.