Catnip is a plant, scientifically known as "Nepeta Cataria".
Originally native in the Europe, now has much widespread in North America.
Cats are known to react to catnip in various ways. Some will rub, roll over it, kick at it, hiss at one another, in short, 'all high and nuts' for several minutes. Then, they will just walk away and ignore it for at least a few hours (or days!). It is important to give the kitties time to 'reset'.
'Nepetalactone' in Catnip triggers the "all high and nuts" response. The catnip reaction is inherited, and some cats are totally unaffected by it. Kittens less than 6 months are known not to respond. Senior cats are less sensitive and needs a longer time to 'reset'. Again, it all depends on Mr or Miss Kitty!
Sometimes, cat owners tell me that their feline masters do not respond to catnip (N.Cataria) - Why?
1.) Their feline masters could be too young or too senior.
2.) Feline masters are born this way! (Just like Lady Gaga!) - as reaction is inherited.
3.) The catnip has been kept too long, thus no longer potent - please avoid those catnip collecting dust on shelves of petshop! To keep it potent, put them in deep-freezer.
4.) There are many versions of Nepeta, but not all has the same Nepetalactone content. So make sure, it is Nepeta Cataria which has white flowers, not purple, pink or whatever BUT white!
There's a plant found locally in Malaysia, known as "Kucing Galak", (Scientific name, "Acalypha Indica") which has a similar effect on cats too. Its roots are particularly potent. This particular plant is said to originates from India. (It is also known as Thai Catnip or Tam Yae Maew)