Those who have cats should avoid giving these pets grapes. Although the exact chemical in grapes that is bad for them is unknown, it is thought to be the flesh of this fruit. Although not all fruits are bad for cats to eat, there are certain ones which have been known to cause certain health problems, such as grapes.
If you must give your cat grapes, you will want to make sure that you do so in moderation so as not to cause any significant health problems.
Peeling the grapes before feeding them to your cat also might decrease the adverse health effects involved in giving this fruit to these animals.