Gluten is a composite of storage proteins termed prolamins and glutelins and 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, related species and hybrids, and products of these (such as malt).
Casein is a family of related phosphoproteins (αS1, αS2, β, κ). These proteins are commonly found in mammalian milk, comprising c. 80% of the proteins in cow's milk and between 20% and 45% of the proteins in human milk. Casein has a wide variety of uses, from being a major component of cheese, to use as a food additive. The purified protein is water insoluble. In addition to being consumed in milk, casein is used in the manufacture of adhesives, binders, protective coatings, plastics (such as for knife handles and knitting needles), fabrics, food additives, and many other products.
A study found that autistic children placed on a casein-free diet for eight weeks showed significant behavior improvements (Lucarelli 1995). In many cases, casein free diets are combined with gluten-free diets and are referred to as a gluten-free, casein-free diet.