Dandruff is a condition marked by flakes of dry skin on the scalp. The flakes can often fall from your hair and land on your shoulders.
Dandruff usually results from a dry scalp. If this is the cause, the flakes are typically small and you may also have dry skin on other parts of your body.
Washing your hair with a harsh shampoo or using a lot of chemicals on your hair can sometimes irritate your scalp and lead to flakes.
A fairly common condition called seborrheic dermatitis is the cause of many dandruff cases. It’s characterized by patches of red and oily skin that leave yellowish flakes on the scalp. These flakes are often larger than the dandruff flakes that can arise from dry skin.
Seborrheic dermatitis can also cause flaky, irritated patches elsewhere on your body, which may lead you to think you have psoriasis.