Cats can have parmesan cheese in very small amounts and only as an infrequent treat. Parmesan cheese is not toxic to cats, but it is high in fat, salt, and calories, which can lead to digestive upset, obesity, and other health issues if fed regularly. Since most adult cats are lactose intolerant and lack the digestive enzymes to break down dairy, cheese is not a natural or necessary part of their diet. Parmesan, being a hard, aged cheese with lower lactose content than some others, is one of the better cheese options for cats if given occasionally in tiny portions. However, it is generally better to offer your cat protein-rich treats like cooked chicken or fish instead. If a cat eats a small amount of parmesan, it usually does not cause serious problems, but it is wise to monitor for any signs of gastrointestinal upset and avoid making it a regular treat.