Any kind of string or yarn is not safe for cats to play with. Cats can easily swallow yarn or any string-like items. Cats have these tongues covered in backward-facing barbs that make it hard for them to spit yarn, string, and similar things. It would be best for your pet’s health and your peace of mind if you find better alternative toys other than a ball of yarn. It may not be possible to separate cats from strings. So many things in the household have strings, like curtains, rugs, clothing, blankets, shoelaces, needlecrafts, and floss, to name a few. None of these things are safe toys for your cat. You can play with such toys with your cat; make sure that you put them away after playtime in a place that your cat cannot reach. Instead of encouraging your cat to play with any string-like objects, provide safer cat toys that can give them equal fun and challenge. Your cat can play with fake mice, small stuffed toys, catnip toys, small balls, and any toys that they can carry or push around than swallow. But check for any loosely glued parts or anything that may be a potential choking hazard. You can give your cat thick, soft pulls to play with, such as your bathrobe belt. Cats like to chase and hold onto things they caught. Soft pulls can be fun to play with but will be harder for your cat to swallow. Giving your cat other toy options than strings keeps your yarn stash secure and your cat safe and happy as well.