Dermatitis Herpetiformis vs Eczema: How to Tell Them Apart

It can be incredibly frustrating to suffer from a severe, relentless rash, especially when treatments don’t seem to work. If you have been diagnosed with severe eczema but suspect you might have dermatitis herpetiformis (DH), you are not alone. DH is frequently misdiagnosed as eczema (atopic dermatitis), bug bites, or allergic reactions, with many patients waiting over two years to get the correct diagnosis ^[1][2]. While both conditions cause intensely itchy skin, DH is actually the skin manifestation of celiac disease—an autoimmune reaction to gluten ^[3][4]. You can often tell the difference by paying close attention to the type of itch (which often burns or stings in DH), the specific symmetrical locations on the body, and the presence of small fluid-filled blisters ^[4]. However, because scratching can make DH look exactly like eczema, a specialized skin biopsy is the only way to definitively tell them apart ^[5][6].

The Itch: Burning vs. Standard Itching

Both DH and eczema are famous for causing intense, unrelenting itchiness ^[7][4]. However, people with DH often describe their itch differently. Before a DH rash even appears on the skin, you may feel an intense burning or stinging sensation in the area. This “pre-rash” burning is a hallmark of DH and is less common in standard eczema, which typically presents as a deep, persistent urge to scratch.

Location, Location, Location: Extensors vs. Flexors

Where the rash appears is one of the strongest clues.

• Dermatitis Herpetiformis: DH is highly symmetrical and prefers the “extensor” surfaces of your body—the outside of your joints. If it appears on your left elbow, it will almost certainly appear on your right elbow at the same time. Common hotspots include both elbows, both knees, the buttocks, the lower back, and the scalp ^[4].
• Eczema: In older children and adults, eczema typically favors the “flexor” surfaces—the inside creases of your joints, such as the elbow pits, behind the knees, and the neck ^[7]. (Note: In infants and toddlers, eczema can frequently appear on the extensor surfaces).

The Look: Blisters vs. Scaly Patches

DH gets the “herpetiformis” part of its name because it forms small, clustered, fluid-filled blisters (vesicles) that resemble herpes cold sores ^[4]. Eczema, on the other hand, typically causes dry, red, scaly, or leathery patches of skin ^[7].

The catch? The itch of DH is so severe that most people scratch the blisters off before they ever get to a doctor’s office ^[4]. Once scratched, DH leaves behind red, crusted sores that look virtually identical to heavily scratched severe eczema or bug bites ^[8].

The Definitive Test: Why a Standard Biopsy Isn’t Enough

Because the scratched rashes look so similar to the naked eye, your doctor cannot diagnose DH just by looking at it ^[2].

To confirm DH, your doctor must perform a specialized test called Direct Immunofluorescence (DIF) ^[9][6]. Here is what you need to know about this crucial test:

• What it looks for: The DIF test uses a special dye to look for granular deposits of an antibody called IgA in the upper layers of your skin (the papillary dermis) ^[10][5]. These deposits are a definitive sign of DH ^[10].
• Where it must be taken: A standard biopsy is taken directly from the center of a rash. However, for a DIF test, the biopsy must be taken from normal-appearing skin immediately next to the rash (perilesional skin) ^[6]. If the biopsy is taken directly from the blister or scratched area, the inflammation will have destroyed the IgA antibodies, leading to a false negative—and a missed diagnosis.

Getting the correct diagnosis is life-changing because the treatments are entirely different. Eczema is managed with topical steroids and moisturizers, while the core treatment for DH is a strict, lifelong gluten-free diet to heal both the skin and the underlying autoimmune response ^[11][5]. Because a gluten-free diet can take months or even years to fully clear the skin, doctors often prescribe a medication called dapsone to provide rapid relief from the severe itching and blistering in the meantime ^[12].

Serological (blood) tests for celiac antibodies, such as the tissue transglutaminase (tTG) IgA test, can also help support the diagnosis ^[13]. However, some patients with DH do not have detectable levels of these antibodies in their blood, which is why the DIF skin biopsy remains the gold standard.