While the Zesty Paws Probiotic Bites are designed to be safe and beneficial for dogs, it is always possible that an individual dog may have a unique reaction or sensitivity. Some potential side effects may include gastrointestinal discomfort or upset, including gas, bloating, or diarrhea. If you notice anything unusual after introducing the product to your dog's routine, it's best to consult with your veterinarian for guidance.