Gluten (wheat gluten) is a special type of water—insoluble proteins found in cereal grains. The most gluten is found in modern wheat and its more ancient types (spelt, spelt and kamut), as well as in barley and rye. Oats do not contain gluten, but wheat often gets into oatmeal, so gluten-free oat flakes can only be considered produced under special conditions. Also, these oat flakes must pass a special check and be marked with a special symbol – "crossed out ear".