How do you know if you have dermatitis herpetiformis? do you have to have rash?

Dermatitis Herpetifo: Dermatitis herpetiformis is an extremely itchy rash made of bumps and blisters. The rash is chronic, which means it continues over a long period of time. A skin biopsy and direct immunofluorescence test of the skin are performed in most cases. Your doctor may also recommend a biopsy of the intestines.

Yes: It's usually a very itchy vesicular rash on elbows and knees and assoc to celiac disease. Avoiding gluten usually improves rash.