The reasons why cats like to suck catnip:

1. Catnip contains an ingredient called nepetalactone. Nepetalactone can cause nervous excitement in cats and cause hallucinations in cats.

2. Nepetalactone in catnip has a similar chemical structure to the substance secreted in the urine of estrous female cats. Male cats are more likely to be attracted to catnip than female cats.

3. Cats are very clean animals. They often lick their fur to keep it clean, and they also inhale some hair. Feeding some catnip in an appropriate amount can induce vomiting and help the cat vomit out hair.

4. Catnip can help cats calm down and relieve anxiety. However, please note that catnip cannot be used when the cat is in estrus, otherwise it may cause the cat to be too excited and run and scratch.

5. Catnip can increase the cat’s appetite. Giving cats catnip to make them feel good will help increase their appetite.