I have hair scalp issue since last 12 years. Sometimes it is there on the mustache as well. Have tried everything but of no use. The colour of the flakes removed from the scalp are white yellowish. It occurs when the sky is dry or when the skin is oily. So the flakes are dry and oily depending on the scalp. Is it seborrheic dermatitis or psoriasis or something else? If someone can answer this I can take forward the treatment.