What is a sign of pityriasis on the scalp?

Pityriasis, also known as dandruff or seborrheic dermatitis, is characterized by the presence of small white or yellowish scales on the scalp. These scales can be dry or oily and often result from the excessive shedding of dead skin cells combined with oil from the scalp. The formation of these small white scales is a primary sign of this condition, indicating an abnormal shedding process or an imbalance in scalp health.

While hair thinning and scalp dryness can occur for various reasons, they are not definitive signs of pityriasis. A greasy scalp might also be present but is more associated with different forms of seborrheic dermatitis rather than the classic presentation of pityriasis that features the distinct small, white scales. Thus, the identification of small white scales is the most accurate indicator of pityriasis on the scalp.