About two thirds of the patients with dermatitis herpetiformis have an enteropathy which responds to treatment with a gluten-free diet. By contrast, their rash is totally unaffected by gluten withdrawal. Likewise, the rash is unaffected by gluten withdrawal in patients with dermatitis herpetiformis who have a normal bowel. Intradermal injection of gluten does not provoke the rash.
The significance of the dose of dapsone required to control the rash is discussed. The minimal effective dose of dapsone is in most patients unaffected by gluten withdrawal.
The relationship of the enteropathy to the rash is an indirect one and patients whose enteropathy is controlled by a gluten-free diet will still need dapsone for their rash.
Marks J, Shuster S. Dermatitis HerpetiformisThe Role of Gluten. Arch Dermatol. 1970;101(4):452-457. doi:10.1001/archderm.1970.04000040074014