Seborrhoeic dermatitis is a common, harmless, scaley rash that sometimes itches. Dandruff is seborrhoeic dermatitis of the scalp. Seborrhoeic dermatitis may also occur on the eyebrows, eye lid edges, ears, the skin near the nose and skin-folds of the armpits and groin. Sometimes seborrhoeic dermatitis produces round, scaling patches on the middle of the chest or on the back.