The picture I linked is of a buckwheat pillow. Had no idea they were a thing before today.
What about silk or bamboo pillow cases?
I've only ever really used cotton pillow cases and cotton stuffed pillows. I recently upgraded to a foam pillow that I'm enjoying.
I feel it's important to note the Purple-brand mattresses and pillows all come coated in a white plastic powder. Sometimes a lot of it.
Breathing in micro/nano plastic powder is not good.
Purple claims it's safe, inert, and non-toxic. The reality is that breathing in powdered plastic is not safe.
I would recommend using a well-sealed allergy-type pillow cover for any purple pillow, at a minimum.
They come with a big thick zip up cover, if that's the kinda thing you're looking for. I don't really remember noticing any powder on mine when I got it, but it's entirely possible I just didn't notice.