Celiac disease, wheat allergy, and gluten intolerance are three separate conditions.
Celiac disease occurs when gluten proteins react with the villi, the particles that line the small intestine to absorb nutrients. The disease can cause inflammation and eventual permanent organ damage. Intestinal pain and diarrhea are common symptoms. A doctor can only properly diagnose celiac disease with a combination of blood tests and an endoscopic biopsy of the small intestine. Sufferers must avoid all products that include gluten, such as pastas, ready-to-eat cereals and breads.
A true wheat allergy has nothing to do with the small intestine. Here, a wheat sensitive antibody in the blood causes allergic hives, sneezing, anaphylaxis, and other unpleasant or dangerous reactions. Technically a wheat allergic person can tolerate gluten from non-wheat products. This condition is very difficult to diagnose. Tests are extremely unreliable.
Gluten intolerance is yet another separate condition. Here, a person feels bloating, confusion, or irregular bowel movements after ingesting gluten products. Many people feel better when they get around to giving up gluten, but a true test for gluten intolerance simply does not exist.