im not sure, but just to be safe i would go with cotton
For bedding and commercial toys arent usually cotton so id say acrylic is fine but if youre really worried about it buy some organic colorgrown cotton its not even dyed.
It shouldn’t be a problem. Just keep an eye on your animal. As long as it doesn’t eat the whole thing, it should be o.k. If it looks like it’s being dstroyed and coming apart, you should remove it. Weird things can happen with loose strings and animals….
dave