The Cause of Dermatitis Herpetiformis

To the Editor.—  In their article on dermatitis herpetiformis, Olbricht et al¹ state that dermatitis herpetiformis is a skin disorder of unknown cause. This is not correct. The rash clears after withdrawal of gluten from the diet² and recurs on reintroduction of gluten.³ Thus, by anybody's definition, the cause of the rash is gluten and is known.