Seborrheic dermatitis is usually caused by susceptibility to a yeast called malassezia furfur which has a propensity for oil or sebum. It can occur on scalp, face, and torso.
Dry scalp can be caused by many skin conditions including eczema or psoriasis. Eczema usually responds to topical steroids whereas sebborheic dermatitis usually requires a topical antifungal in addition to a steroid.
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