Gluten is a word that refers to the proteins gliadin and glutenin, found in certain grains.
What grains contains gluten?*
-wheat (Triticum spp.)
-rye (Secale cereale)
-barley (Hordeum vulgare)
-kamut (Triticum turanicum - also known as T. turgidum subsp. turanicum)
-spelt aka dinkle (Triticum spelta)
-bread wheat (Triticum aestivum)
-bulgur (made from wheat, usually durum wheat - Triticum durum or Triticum turgidum durum)
-semolina (made from durum wheat Triticum durum)
-triticale ( is a hybrid of wheat and rye -Triticosecale)
-emmer wheat aka farro (Triticum dicoccon)
I added the Latin terms because the "tricicum" genus is helpful. Wheat, rye and barley all belong to the taxonomy tribe triticeae; the red flag that indicates GLUTEN IS HERE.
The Oat Exception
Oats, (Avena sativa), do not contain gliadin or glutenin, but many people who are alergic or intollerant of gluten, react to oats. This is because:
1. Oats grown, harvested, stored and processed on/with shared equipment with gluten-containing grains are contaminated.
2. Oats contain different protein structures, avenin, which some persons with Celiac Disease have avenin-reactive mucosal T-cells, which might cause intestinal villi damage. (Some people have a gluten-like reaction to avenin, thus also need also avoid oats in addition to gluten-contianing grains.)
Certified gluten-free oats are available in some specialty food stores and online. Some people tolerate them, others do not.
*For a full list and more common names and products containing gluten, visit celiac.com