According to Paw Nation, dogs can eat small amounts of bread safely. It can cause weight gain and indigestion if fed in excess. The American Society for the Prevention of Cruelty to Animals warns that uncooked bread dough should never be fed to dogs.
The ASPCA states that uncooked bread dough contains live yeast that can grow in the dog's stomach and cause the stomach to swell dangerously. The yeast can also produce alcohol in the dog's digestive system, causing alcohol poisoning. Before the development of commercial dog food, bread was commonly fed to dogs. One recipe described by Wikipedia consisted of mixing the liver, heart and blood of a stag with bread, milk and cheese.