Cats typically react to catnip by rolling around, purring, and meowing. Catnip contains a chemical called nepetalactone, which cats find attractive. When cats smell or ingest nepetalactone, it can have a calming effect on them. It can also stimulate their playfulness and cause them to act in an excited or euphoric manner. Catnip is non addictive and is generally safe for cats, although some cats may be more sensitive to its effects than others.