So what is gluten anyway?

Gluten is the elastic protein commonly found in rye, wheat, and barley. Technically, these proteins are called gliadin and glutenin. Grains that do not have gluten include wild rice, corn, buckwheat, millet, amaranth, quinoa, teff, oats (there is some controversy about this), soybeans, and sunflower seeds. But gluten is not restricted to just grains. It is hidden in thousands of products. For example as a stabilizing agent or thickener in products like ice cream and ketchup. Still, wheat is where you'll find gluten 90% of the time.

Between 0% and 1% of the United States population are sensitive to gluten due to celiac disease. Celiac disease is an autoimmune disorder of the small intestine which can produce a wide range of gastrointestinal symptoms. You can also be gluten intolerant or have a gluten allergy without actually having celiac disease. Gluten damages the small intestines of people with celiac disease, and makes life very uncomfortable for people with gluten sensitivity.