Erythema, crusting with dandruff on the scalp can be considered to be caused by seborrheic dermatitis, eczema or tinea capitis, psoriasis and other causes. 1. Seborrheic dermatitis: it can occur in seborrheic areas, such as the head, face, chest and back, etc. It can be associated with increased lipids, Malassezia colonization, immune response, etc. It often manifests itself as erythema and furfuraceous dandruff, with hair loss, and there can be oily scabs attached to the scalp with obvious inflammation underneath the scabs, vesiculation, and oozing. 2. Eczema: allergic inflammatory reaction, can occur in the scalp, acute stage can have erythema, papules and oozing, oozing more, revealing red moist vesicles, long lasting can be on the surface of the crust and scales. 3. Tinea capitis: after the infection of the scalp by dermatophytes, it can cause tinea capitis, in which tinea cruris, the lesions are yellowish red spots covered with flaky scales at the beginning, and then yellowish scabs can be formed later, and the serious ones can cover the whole scalp. 4. Psoriasis: the main symptom is red spots on the skin, covered with silvery-white scales, so there can also be red spots on the scalp, scabs and dandruff symptoms. If scalp erythema, crusting and flaking, it is recommended to consult a doctor in time, after a clear diagnosis, follow the doctor’s instructions for treatment.