This National Institutes of Health Publication 11-5755, "What I Need to Know About Celiac Disease," provides information from understanding what Celiac Disease is, what the symptoms are, and obtaining the proper treatment and proper nutrition for Celiac Disease. Celiac disease is an immune disease in which people can't eat gluten because it will damage their small intestine. Gluten is a protein found in wheat, rye, and barley. Gluten may also be used in products such as vitamin and nutrient supplements, lip balms, and some medicines. Other names for celiac disease are celiac sprue and gluten intolerance. Your body's natural defense system, called the immune system, keeps you healthy by fighting against things that can make you sick, such as bacteria and viruses. When people with celiac disease eat gluten their body's immune system reacts to the gluten by attacking the lining of the small intestine. The immune system's reaction to gluten damages small, fingerlike growths called villi. When the villi are damaged, the body cannot get the nutrients it needs.