Cats generally won’t vomit if you use too much catnip. Catnip is not harmful to cats. But owners should not use too much catnip on their cats. It is not a good thing if it is too irritating to the cats. ​​​​​​

Some cats will have an uncomfortable reaction to catnip after being overstimulated by catnip. The most likely result is that the cat is no longer interested in catnip. Breathing in too much catnip can cause respiratory problems in your cat.