Dandruff is a common scalp problem that causes flaking and itching. The main cause of dandruff is seborrheic dermatitis, a skin condition that causes irritation and flaking of the scalp. Malassezia yeast is also a major factor in the development of dandruff. Hair care habits such as not washing your hair enough or too much, and using the wrong hair products can cause dandruff to appear and worsen. Additionally, other factors such as sun exposure, poor diet, and exposure to dust can also aggravate dandruff. In particular, people with diseases such as Parkinson's, HIV, or medical conditions that weaken the immune system are at higher risk of dandruff.