Healthy cats do not drool. However, it
is common for cats to drool when they know they are going to be given an
unpleasant-tasting medicine or receive an injection. This is psychological. A
few cats will also drool when they are purring and very relaxed. It is
important to know what is normal for your individual cat.
Keep in mind that an animal who drools excessively and acts irrationally
could have rabies. Exercise great caution in handling such an animal.
Cats can develop a fear of people they don’t know for many reasons. Companion felines have unique personalities, and some are just more outgoing than others. However, if a cat is calm and friendly with his family but afraid of visitors, it’s often because he didn’t have enough experience meeting new people when he was very young. To be social and comfortable with all kinds of people, a cat must have frequent opportunities to meet numerous new and different people in low-key, pleasant circumstances...
Drooling accompanied by signs of ill health, such as watering of the eyes,
is quite likely due to a feline viral respiratory infection. Young cats with liver shunts
will drool excessively. Mouth infections and foreign bodies in the mouth are
accompanied by drooling. Heat stroke can cause excess salivation, as can
certain poisons (such as insecticides and arsenic).
Treatment: This is contingent on identifying the cause of the drooling.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"