A large piece of hard dandruff on the head is considered to have the following possibilities: in the first case, psoriasis is considered, divided into common psoriasis, arthritic psoriasis, erythrodermic psoriasis and pustular psoriasis, all of the above types can appear a relatively hard large piece of dandruff, this disease is mainly due to infection or smoking, trauma, genetics and other factors. Erythrodermic psoriasis as well as pustular psoriasis are mostly triggered by bad drug stimulation on top of having common psoriasis. In the second case, consider hair erysipelas. The cause of this disease is not clear, may be related to vitamin A deficiency or genetic factors, immune disorders and other factors, in clinical treatment can be applied fluticasone propionate ointment, once a day for treatment.