Celiac disease is a digestive disease that damages the small intestine and interferes with absorption of nutrients from food. People who have celiac disease cannot tolerate gluten, a protein in wheat, rye, and barley. Gluten is found mainly in foods but may also be found in everyday products such as medicines, vitamins, and lip balms.
Gluten: The Whole Story - a great article on the difference between gluten intolerance and celiac disease and what tests you can do to figure out if you have either. Both the author and I agree that the gold standard for testing is eliminating gluten for at least 6 weeks. Then reintroduce, and watch for adverse symptoms for the next 4 days.