Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Dermatitis herpetiformis ?
    ### Response:
    Dermatitis herpetiformis is a rare, chronic, skin disorder characterized by groups of severely itchy blisters and raised skin lesions. These are more common on the knees, elbows, buttocks and shoulder blades. The slow onset of symptoms usually begins during adulthood, but children can also be affected.
    