Carlos avoids the ingredient list of packaged foods because he has celiac disease.

wheat, rye, and barley

Explanation:

Celiac disease is a type of an immune disorder in which a person is unable to eat food that contains gluten because it can lead to the destruction of their small intestine. Gluten is a type of protein that is found in several ingredients such as wheat, rye, and barley. Consumption of gluten can lead to the development of inflammation in the small intestine which after a certain time can lead to its destruction. The various symptoms associated with the disease include bloating, diarrhea, anemia, etc.Since Carlos has celiac disease he has to avoid wheat, rye, and barley.