The primary objective of this study is to evaluate the efficacy of dapsone gel, 5% in the treatment of dermatitis herpetiformis. The primary efficacy end point will be the proportion of patients achieving success based on mean % reduction from baseline in total lesion counts at week six. Success for lesion reduction will be defined as statistically greater mean percent reductions at week six in the dapsone gel-treated extremity compared with the control extremity of each patient.