Gluten is a protein found in wheat, barley, and rye. People who have gluten-free diet do not eat wheat, barley, rye and any foods that include these. Foods that include gluten are bread, pasta, and cakes. Also some alcohol drinks has gluten present in them, including beer and malt spirits. On the food market, there are many substitute products, such as gluten-free bread. Some foods such as rice, polenta, and cheese are naturally gluten-free.
The main reason why people have gluten free diet is that they have a diagnosis of coeliac disease or dermatitis herpetiformis.