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.
Dehydration is an imbalance of water and electrolytes (minerals) in the body, and can cause serious complications for pets and people alike. Water is essential to cats, who depend on proper daily fluid intake to maintain appropriate health and replace fluids that are routinely lost through urine, feces and respiration. Water makes up 80 percent of your cat’s body, and is necessary for all his biological processes, including circulation, digestion and waste removal.
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"