Gluten is the main protein found in various grains such as wheat, barley and rye and is known to cause an immune reaction in people with celiac disease. If you are at risk of celiac disease (family history and possess the variant on the HLA-DQA1 gene) and/or experience symptoms such as chronic bowel upsets, joint pain, inflammation and migraines after consuming gluten products you should try avoiding gluten completely to see whether your symptoms improve.
If you are gluten sensitive, you may be able to re-introduce gluten into your diet once your digestive system has healed.
If you are celiac, you should stay away from gluten for life.