Probiotics should be given based on the recommendation of your veterinarian. They are not recommended for pets that are critically ill or that have a suppressed immune system, or in animals that are severely dehydrated or vomiting. There are no known side effects with Proviable when given according to package recommendations. Proviable-KP Paste should only be used for 48-72 hours unless directed otherwise by your veterinarian, as the kaolin and pectin could potentially cause constipation with prolonged use at higher than recommended levels.