Inflammation of the skin, usually itchy, with redness, swelling, and blistering. Causes and patterns vary. Contact dermatitis appears at the site of contact with an irritating substance or allergen. Atopic dermatitis, with patches of dry skin, occurs in infants, children, and young adults with genetic hypersensitivities (atopy). Stasis dermatitis affects the ankles and lower legs because of chronic poor blood flow in the veins. Seborrheic dermatitis appears as scaly skin, most often on the scalp (dandruff) and areas rich in sebaceous glands. Neurodermatitis is apparently caused by repeated scratching of an itchy skin area.