Hi, the most common cause of hypersalivation in cats is exposure to flea treatment. Have you used this recently? or any other meds like wormers? There are also potential toxins such as plants, toads and other chemicals that can trigger hypersalivation.Dental disease can also be a cause. I would recommend seeing your vet to determine the cause and deal with the primary problem. If a primary problem is not found or toxins are not suspected an injection of low dose atropine can be used to control the overflowing saliva. This works really quickly. If there is any dehydration from the loss of saliva some subcutaneous fluids may be administered by your vet too. Hope that helps.