Why do cats like to smell catnip?
Catnip balls are made from catnip. Catnip can have some strange effects on a cat's behavior. Rich in aromatic essential oils, catnip releases a strong and complex fragrance with just a slight touch. Whenever a cat smells this scent, it may become unusually excited and roll around; it may happily eat a few bites of the catnip; or it may squint its eyes and become unusually intoxicated. The reactions vary, and the cats are completely different from before they smelled the catnip. 
When catnip is touched, it releases a substance called nepetalactone. Its scent stimulates the cat's neurons through its sensitive nose, which then transmits the signal to the cat's brain. The olfactory bulb, amygdala, and hypothalamus in the brain all react, and the cat starts drooling, rolling around, and frantically rubbing its face against the catnip.
Studies show that catnip's effect on cats is not addictive. Most cats return to normal and lose interest in the plant within 5-15 minutes after smelling it. The longest addiction usually lasts no more than an hour. After experiencing catnip's allure once, cats will not regain interest in it for at least 2 hours.
