Avenin is a protein found in oats. It is structurally similar to the gluten protein found in wheat, barley, and rye, but it is generally considered to have a lower toxicity level for individuals with celiac disease. However, some people with celiac disease or gluten sensitivities may still react to avenin, which is why it's important for them to choose certified gluten-free oats or alternative grains for their dietary needs.