Catnip is perennial herb and member of the mint family. Its active ingredient nepetalactone is found mostly in its leaves and stems. Only about 50% of cats respond to catnip, and of those 50% the response is widely variable in behavior. Catnip is not considered harmful and the responses vary from sedation to hyper activity. Most people use it to attract their cat to a scratching post or to increase playtime with toys.