It has antiseptic properties certainly, but the reason cats and another animals lick wounds is firstly because it promotes and accelerates the healing process, and secondly because it is believed the reduce pain and itching by overloading the pain receptors in the skin. We humans do the same thing why is why you have the urge to scratch a healing wound.
Too much licking may well lead to infection - but not from the licking itself, rather from an infected lick granuloma. This, and the potential for biting a wound and introducing bacteria into the bloodstream, is why a vet might recommend a collar if the animal will not leave the wound alone
