Bread is not toxic. However, there is nothing in bread that provides any of the nutrition a dog needs.
Yes, dog can eat bread only if it is
1. Baked and fresh (not stale)
2. In small moderate amounts (that is, less than half a slice) and not given on a regular basis. Some people use it as an occasional treat.
Why unbaked bread or dough should be kept out of reach from your dog?
Before the bread is baked, the yeast dough needs to rise. So when your dog consumes the dough, the warm environment of the stomach acts as an oven and encourages the dough to continue rising and swells inside your dog’s tummy. This could result in severe pain or bowel obstruction in what is called a “distended or bloated abdomen”.
In serious cases, the stomach may then twist leading to a rupture in it or one of the intestines. This is a life-threatening situation that requires emergency abdominal surgery before the walls of the stomach die due to poor blood supply.
In addition, when the yeast ferments the dough to make it rise, it produces alcohol that can also lead to alcohol poisoning in your dog.
Why only small amount should be given?
1) Since there is no nutritional benefit of bread to a dog, there is no reason to give it at all in the first place.
2) There have been cases of dogs getting sick after consuming bread. Mild reactions include gasses in the stomach, lots of farting, digestive problems such as blockage & constipation. The bread gets clogged in a dog’s digestive system and makes it more difficult for the dog to defecate and the dog may also vomit.