Diagnosis of Dermatitis Herpetiformis
A skin biopsy is used to confirm a diagnosis of DH. Dermatologists usually use what’s called a "punch biopsy" to remove the skin and test it for dermatitis herpetiformis. After injecting a local anesthetic, your dermatologist will use a tiny, cookie-cutter-like punch to remove a 4mm sample of skin. The incision can be closed with one stitch, and generally heals with very little scarring.

A skin sample is taken from the area immediately next to a lesion and a fluorescent dye is used to look for the presence of Immunoglobulin A (IgA) deposits that appear in a granular pattern. Skin biopsies of people with DH are almost always positive for this granular IgA pattern.

It is important to have your dermatitis herpetiformis skin biopsy performed by someone who has diagnosed the skin condition before and knows how to do the biopsy. The skin sample must be taken from skin directly adjacent to the suspected dermatitis herpetiformis lesion, as opposed to directly from the lesion, since inflammation in the lesion can destroy the IgA deposits.

Blood tests for other antibodies commonly found in people with celiac disease –antiendomysial and anti-tissue transglutaminase antibodies – supplement the diagnostic process. If the antibody tests are positive and the skin biopsy has the typical findings of DH, patients do not need an intestinal biopsy to confirm the diagnosis of celiac disease.