What Is Gluten? Gluten is a type of protein found in grains, including wheat, barley and rye. Gluten Intolerance? Gluten sensitivity or intolerance is a condition that causes a person to react after ingesting gluten, a protein found in wheat, barley and rye. Gluten causes an autoimmune response in the body which damages the small intestine. … Continue reading 10 Warning Signs of Gluten Intolerance That Most People Ignore