Coeliac disease is an immune disorder affecting the small intestine. An abnormal immune response to the consumption of gluten can prompt the production of several different autoantibodies (antibodies which attack ones own proteins). It is not an allergy - it cannot cause an anaphylactic reaction - but it is an intolerance to gluten, which is a protein found in wheat, barley, rye, and oats.
It is diagnosed through a combination of blood tests, and biopsies of the duodenum (the first section of the small intestine, immediately following the stomach).
Damange to the small intestine can result in malabsoption of nutrients, causing aenemia, osteoporosis, weight loss, fatigue, and other conditions bought on by deficincies of essential viatmins and minerals.
In the long term, untreated coeliac disease can lead to a higher risk of specific cancers, and other serious conditions.
The only effective treatment is to follow a completely gluten-free diet. The consumption of even small amounts of gluten can cause the production of autoantibodies, which will continue to damage the small intestine and other organs. However, with adherence to the gluten-free diet, the small intestine should mostly heal within 6-24 months.