What causes dandruff to appear in patches on the scalp?

Dandruff appearing in patches may be caused by conditions such as seborrheic dermatitis or tinea capitis: 1. **Seborrheic Dermatitis**: If patients have irregular作息 (作息 should be translated as作息 habits or lifestyle routine, but here it is better omitted for fluency), frequently stay up late, or consume excessive oily or spicy foods, it may easily lead to overproduction of scalp sebum, causing seborrheic dermatitis. The main symptoms include increased dandruff, itching, and red patches on the scalp. Some patients may experience dandruff in patches. Treatment options include selenium sulfide shampoo, desonide cream, and maintaining cleanliness and dryness of the scalp. 2. **Tinea Capitis**: If patients neglect scalp hygiene and skin cleanliness, excessive sebum secretion may easily lead to bacterial growth, causing tinea capitis. Common symptoms include papules on the scalp, mild itching, and flaking. A few patients may also develop patchy dandruff. Treatment options include ketoconazole cream, itraconazole capsules, among others.