Which condition is characterized by excessive oiliness on the scalp?

The condition characterized by excessive oiliness on the scalp is seborrhea. This condition arises from the overproduction of sebum, which is the natural oil made by the sebaceous glands. Seborrhea can lead to oily hair and scalp, and it may also result in flaking, scaling, or redness of the skin in severe cases.

In contrast, psoriasis is a chronic skin condition marked by rapid skin cell turnover, leading to thick, red patches with white scales, but it is not primarily characterized by oiliness. Dandruff may involve the presence of flakes and can accompany oily or dry scalps, but it doesn't necessarily denote excessive oiliness like seborrhea does. Alopecia refers to hair loss and does not involve oiliness of the scalp. Understanding these distinctions is crucial for accurately identifying and addressing scalp conditions in cosmetology practice.