Dermatitis Herpetiformis is a type of Celiac disease that results in an extremely itchy, severe skin rash. If you have dermatitis herpetiformis, you have Celiac disease but not necessarily the other way around. Due to individual scratching the itchy rash, blisters and lesions form. The rash can occur anywhere on the body but usually occurs on the knees, elbows, buttocks, back of the neck, and scalp. The rash happens when a person ingests gluten. Dermatitis herpetiformis is diagnosed by a biopsy of the skin next to (but not directly in) a lesion. Anesthesia is usually used. If Celiac disease is diagnosed, an intestinal biopsy is not needed. The individual may or may not have small intestinal damage, but only a small percentage have gastrointestinal symptoms.