In an informative episode of the online trivia series Today I Found Out, host Simon Whistler explained how catnip causes cats to rub their faces against things. It is believed that nepetalactone, a chemical compound in catnip activates a felines facial pheromones, causing them to act a bit goofy for a short period before the effect wears off. Catnip is not addictive, however too much catnip can cause the appearance of an overdose, however without residual effects.
I’ve personally seen a cat that got into a bulk bag of catnip that was about five times the size of the cat. The poor cat was found with catnip all over itself and more or less half buried in it. As a result of this, for whatever reason, she was mostly unresponsive, was twitching and making random noises, and had a significant amount of drool in her fur around her head and mouth. …Unlike a person who’s overdosed on a drug, though, once the cat was extracted from her self made catnip bed and washed off…within about 15 minutes of that she was completely back to normal with no residual effects.