Gluten is a protein found in wheat and related grain species. Due to its cohesive and viscoelastic properties, giving a chewy texture in the final product, it is used as an extender in processed foods and is also contained in cosmetics.

Individuals with celiac disease, a permanent intolerance to ingest gluten, show adverse reactions to gluten containing foods. Affected individuals attempt to avoid all sources of wheat and grain products. A gluten-free diet also requires meticulous reading of the product labels to avoid exposure to hidden sources of gluten.

According to the Food Information to Consumers Regulation (EU) No 1169/2011, gluten has to be labelled if present in the final product. The same applies to energy drinks.