Sunflower seeds are not really toxic to dogs. If your puppy has eaten in large quantities. Then your dog may be affected by pancreatitis, which is indicated by vomiting, loss of appetite, depression, and pain in the abdomen. Take him to the vet if any signs. However, this is rare and indicates that your puppy had eaten sunflower seeds within the last 24 hours. If not, then your puppy should be fine.