The term ‘catnip’ is thought to originate from the response cats show towards the plant. What happens when my cat has catnip? The active ingredient nepetalactone, is an essential oil which alters the behaviour of domestic and other cat species. Around half to two thirds of cats will respond to this oil. Kitten may not react and only develop the full behavioural change at an older age. Visit our cat toys store and get some fun cat nip toys!