Gluten Is a Protein That Isn’t Present Until You Start Baking
Plain old wheat flour doesn't have gluten in it until you do something with it. Gluten is formed with two proteins, gliadin and glutenin, that bind during the cooking (or digestive) process.
Non-wheat flours can still produce gluten!
Its homologous seed storage proteins, in barley, are referred to as hordeins, in rye, secalins, and in oats, avenins. These protein classes are collectively referred to as "gluten". The storage proteins in other grains, such as maize (zeins) and rice (rice protein), are sometimes called gluten, but they do not cause harmful effects in people with celiac disease.