Seborrheic dermatitis is a common, inflammatory skin condition that causes flaky, white to yellowish scales to form on oily areas such as the scalp or inside the ear. These scales can occur with or without underlying reddened skin. In addition to causing psychological distress, low self esteem, and embarrassment, seborrheic dermatitis is associated with scalp pruritus (itch). Treatment modalities exist to control scalp flaking and itch associated with seborrheic dermatitis, although such therapies often lose efficacy over time. As seborrheic dermatitis is a chronic (life-long) condition, better treatments are needed. The investigators propose to better characterize in subjects with seborrheic dermatitis involving the scalp versus normal scalp controls: (a) the clinical characteristics of the associated itch and (b) the pattern of nerve innervation to the scalp. In this way, the investigators hope to get a comprehensive understanding of the factors causing scalp itch with the aim that this information will create new candidates to which treatment modalities can be designed. At least 12 (up to 20) subjects and similar number of control subjects without disease will have one clinic visit including questionnaires, testing of sensation on the scalp, and biopsy of the scalp.