SubDerm: What is Seb Derm? Seb Derm (aka seborrheic dermatitis, seborrheic dermatitis AmE, seborrhea, seborrheic eczema) is an inflammatory skin disorder affecting the scalp, face, and torso. Typically, seb derm presents with scaly, flaky, itchy, and red skin. It particularly affects the sebaceous-gland-rich areas of skin. In adolescents and adults, seb derm usually presents as scalp scaling similar to dandruff or as mild to marked erythema of the nasolabial fold ("smile lines" or "laugh lines",