What has gluten in it?
Gluten
Gluten (from Latin gluten, "glue") is a composite of storage proteins termed prolamins and glutelins[1] that is stored together with starch in the endosperm (which nourishes the embryonic plant during germination) of various cereal (grass) grains. It is found in wheat, barley, rye, oats and related species and hybrids (such as spelt, khorasan, emmer, einkorn, triticale, etc.),[2] as well as products derived from these grains (such as breads and malts). Glutens, and most especially the Triticeae glutens, are appreciated for their viscoelastic properties,[3][4] which give dough its elasticity, helping it rise and keep its shape and often leaving the final product with a chewy texture.
Shampoo
Many people suffer from eczema on their palms and their head. Some find that wheat or gluten — the protein found in many grains including wheat — is the cause, particularly if they are sensitive to foods containing gluten (citation needed). Shampoo can inadvertently enter the mouth, particularly among children, so all individuals who are on gluten-free diets may prefer to use a gluten-free shampoo. Shampoo manufacturers are starting to recognize this and gluten-free and wheat-free products are now available.