Why is celiacs concidered a disease and not a food allergy? isn't it just an allergy to gluten?

No: Celiac disease is not an allergy. It is a reaction or sensitivity to gliadin in gluten which is contained in wheat, rye, and barley by the small intestine causing a flattening of the inner lining or villi which causes malabsorption of various nutrients leading to a variety of GI and non-gi symptoms. It is thought to be an autoimmune phenomenon as antibodies to body tissue & enzymes are often found.

It all depends: Scientifically an allergic reaction is what happens when you have developed allergic antibody (IgE) to an agent and then have an histamine reaction as re-exposed. With this in mind the symptoms of Celiac disease and contact dermatitis are caused by the reactions of your immune cells that are trying to kill your own cells that are contaminated by touching the gluten, poison ivy or nickel in metals