Talking about a bread allergy is not really accurate. Bread is made of a variety of ingredients. If you are “allergic to bread” then you are surely allergic to other foods made up of some of the same ingredients.
Also, consider that bread is made of flour (ignoring the type of flour for now) and realize that by grinding the grain into tiny particles, the food oxidizes, making it rather toxic to your body.
Also, bread is so easy to eat, so it is easy to become lazy with meals and snacks, eating far too much bread, resulting in far too much carbohydrate intake.
Some breads have specific ingredients that may be a problem for you. This means that if you eat certain types of bread, and they have something in them that makes you sick, you may tie your symptoms to the bread, even though it is a particular type of bread with a particular ingredient in it that you can’t tolerate. Examples include:
Check the ingredients of the bread you eat to look for clues.