The diagnosis may be confirmed by a simple blood test for IgA antibodies against tissue transglutaminase (which cross-react with epidermal transglutaminase), and by a skin biopsy in which the pattern of IgA deposits in the dermal papillae, revealed by direct immunofluorescence, distinguishes it from linear IgA bullous dermatosis and other forms of dermatitis. Additionally, the concomitant diagnosis of Celiac disease can be made without the need for a small-intenstinal biopsy if an individual has biopsy-confirmed dermatitis herpetiformis as well as supporting serologic studies (elevated levels of IgA tissue transglutaminase antibodies, IgA epidermal transglutaminase antibodies, or IgA endomysial antibodies). These tests should be performed before the patient starts on a gluten-free diet, otherwise they might produce false negatives. As with ordinary celiac disease, IgA against transglutaminase disappears (often within months) when patients eliminate gluten from their diet. Thus, for both groups of patients, it may be necessary to restart gluten for several weeks before testing may be done reliably. In 2010, Cutis reported an eruption labelled gluten-sensitive dermatitis which is clinically indistinguishable from dermatitis herpetiformis, but lacks the IgA connection, similar to gastrointestinal symptoms mimicking coeliac disease but without the diagnostic immunological markers. Treatment
First-line therapy
A strict gluten-free diet must be followed, and usually, this treatment will be a lifelong requirement. Avoidance of gluten will reduce any associated intestinal damage and the risk of other complications. It can be very difficult to maintain a strict gluten-free diet, however, as contamination with gluten is common in many supposedly gluten-free foods and restaurants.
There is a slight male predominance in DH for unknown reasons and it is associated with celiac disease and the haplotypes HLA-DQ2 and, less commonly, HLA-DQ8. Notable cases
It has been suggested that French revolutionary Jean-Paul Marat had DH. Marat was known to have a painful skin disease, from which he could only achieve relief by immersing himself in a bathtub filled with an herbal mixture; it was in this tub that he was famously assassinated, as portrayed in The Death of Marat. A researcher suggested in 1979 that the mysterious skin disease was DH based on these symptoms and this regimen of self-treatment. See also
Pemphigus herpetiformis
Dyshidrosis

References
Further reading
Kárpáti S (2012). "Dermatitis herpetiformis". Clinics in Dermatology (Review). 30 (1): 56–9. doi:10.1016/j.clindermatol.2011.03.010. PMID 22137227. S2CID 206774423. External links

Pictures: DermNet NZ
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DermNet immune/dermatitis-herpetiformisJournal of Investigative Dermatology