Long dander on the head consider the possibility of the following diseases: 1, common psoriasis, is a chronic inflammatory skin disease, the cause is not completely clear, can be related to immune abnormalities, genetics, infection, endocrine and other factors. The scalp is covered with thick scaly erythematous plaques with clear borders, which can be fused into patches. You can see bundles of hair.2. Consider seborrheic dermatitis, which can be due to vitamin deficiency or infection and other factors that lead to the appearance of fine scales, which can be treated by applying selenium disulfide lotion to wash the hair.