So have you ever wondered, what is the difference between a wheat/gluten allergy, gluten intolerance/sensitivity, and Celiac? Often, these terms are used interchangeably. However, it is important to know that they are three separate things.
Let's start with the allergy thing. A food allergy is an immune reaction to a specific food. Basically what happens is that this great stuff made by our immune system called IgE, which is really an antibody, forms when the body recognizes something as an allergy. So the next time you ingest the offending food, or antigen, again, this IgE creates a whole host of problems, including swelling, asthma, itching, inflammation, vomiting, and lots of other ugly things. When this reaction is very severe, it is called anaphylactic and can be life-threatening.
Ok, so now we've got gluten intolerance and gluten sensitivity. These are two catchall terms. Basically, these two are the same thing. And while they exist in conjunction with Celiac Disease, they can exist separately... a little confusing, huh? It's kind of along the same line as lactose intolerance, your body is lacking an enzyme that makes the break down of lactose possible. In those with gluten intolerance, their bodies are unable to properly breakdown gluten, causing them to be ill. However, whether this causes long term damage to your health is still a very controversial issue. A word of caution: sometimes there are other reasons for gluten intolerance. There may be an underlying illness, so if your symptoms do not improve on a gluten free diet, please get yourself to the doctor.
And finally we've come to Celiac Disease. Celiac is an autoimmune disease in which the body attacks the villi of the small intestine. Which is really not good, since that's where many of the nutrients that are necessary for life are absorbed. However, with this AI disease, the trigger is known, which is a definite plus in staying healthy. When gluten is ingested, instead of being broken down normally in the stomach and small intestine, it becomes resistant to the enzymes that break it down. What's left is a long chain of amino acids, the toxic portion of gliadin. The chain then somehow works it's way into the wall of the small intestine, underneath the cells lining the villi. The small intestine becomes inflammed to protect the body from "the invader". (Insert scary music here...) Over time, this continued reaction causes the villi to lose their integrity, as if having been burned. There's more reasons why a strict gluten free diet is necessary, but that's another topic.
So there you have it! A lot more science than you came here for. But look how much smarter you are!