Dandelions are safe for dogs and work like a charm in a sensitive stomach. The plant can not cause diarrhea in dogs but give health benefits to your pooch. However, overfeeding of dandelions might cause diarrhea in your puppy. Also consuming fresh green dandelions might be contaminated with herbicides and pesticides and other artificial chemicals can lead your dog to diarrhea. So wash the plant before serving to your pet.