Excessive or severe dandruff with itching is usually caused by a condition called seborrheic dermatitis. It generally affects other body areas also in addition to the scalp, including the forehead, naso-labial fold, eyelash and eyebrow regions, and the outer ear. This is a serious problem and requires medical treatment.Cradle cap is the term used when seborrheic dermatitis affects the scalp of infants. It occurs within a week or two after birth. It is characterized by dirty, yellowish, thin or thick crusts on the top of head (vertex) with little itching and no inflammation. The condition usually subsides by itself unless complicated by infection or dermatitis.