While walnut shell litter is a great option for many cats, there is a risk of allergic reactions in humans or cats with nut allergies. If you’re not sure if your cat has a nut allergy, try testing a small amount of litter and monitoring your cat for irritation.

You might also notice more tracking with walnut shell litter. While you can keep this to a minimum with a litter-trapping mat, you might need to sweep up a little more frequently around your cat’s litter box.