Dermatitis Herpetiformis Diagnosed With Skin Biopsy

Dermatitis herpetiformis, a.k.a. "the gluten rash," is an itchy, stinging skin condition associated with celiac disease. It may be the itchiest rash ever, and it's usually is diagnosed through a skin biopsy.

If your dermatologist suspects your itchy rash could be dermatitis herpetiformis, she'll almost certainly recommend a skin biopsy to confirm her diagnosis. Here's what to expect from the skin biopsy procedure and what the results might show.​

Skin Biopsy Looks for Deposits Under the Skin

Your dermatologist will tell you that lots of rashes look alike. What sets "the gluten rash" apart is deposits of a particular antibody in a particular pattern under your skin by the rash.

The antibody is immunoglobulin A, and it's produced by your body, mainly in your intestines. If you have dermatitis herpetiformis, the rash will contain this antibody in a distinctive granular pattern. These deposits, in their specific pattern, are the hallmark of the gluten rash.

You can't see immunoglobulin A with the naked eye. To identify these deposits, your dermatologist must remove a sample of skin, stain it with a dye and look at it under a microscope. If immunoglobulin A deposits are present and in the correct pattern, then the person will be diagnosed with dermatitis herpetiformis.

What to Expect From the Skin Biopsy Procedure

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 sample of skin that's about 4 millimeters (less than 1/4 of an inch) in diameter. The incision can be closed with one stitch and generally heals with very little scarring.

It's 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 the 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.

Treatment Is the Gluten-Free Diet

If your biopsy comes out positive and you're diagnosed with dermatitis herpetiformis, your dermatologist may prescribe dapsone for short-term relief from the itching.

However, you'll need to follow the gluten-free diet to control your dermatitis herpetiformis long-term.