What is celiac disease, what are it's causes and symptoms?how is it diagnosed?

Reaction to gluten: Celiac disease is a condition that damages the lining of the small intestine and prevents it from absorbing parts of food that are important for staying healthy. The damage is due to a reaction to eating gluten, which is found in wheat, barley, rye, and possibly oats. Symptoms include diarrhea (or even constipation) and bloating. Blood test can look for special antibodies and biopsy can confirm.

Celiac disease: In Celiac disease the body reacts to gluten (in wheat and gluten like proteins in rye and barley) in the small intestine causing damage. This limits the intestine's ability to absorb some nutrients. Classically people have loose stool, bloating, and abdominal discomfort but more often are just found when screened for other reasons (like symptoms of a nutritional deficiency like iron or bone loss).