A lot of hair loss when scratching may be related to seborrheic dermatitis, baldness, chemotherapy and other factors. 1. Seborrheic dermatitis: If the roots of the hair fall with white muddy material when you scratch your hair, it is likely to be caused by seborrheic dermatitis. It may be due to inflammation of the scalp due to sebum overflow, and the inflammatory cells harm the local hair follicles, which can lead to a lot of hair loss when you scratch your hair. 2. Patchy baldness: Patchy baldness refers to sudden, limited patchy hair loss caused by endocrine disorders, emotional stress, genetic factors, autoimmune abnormalities, etc., so it will produce a lot of hair loss when you scratch the phenomenon. 3. Chemotherapy: when doing chemotherapy, the toxic effect of chemotherapy drugs will inhibit the proliferation of scalp cells, so that the hair follicles are damaged, which leads to a lot of hair loss when you scratch. If the hair falls out a lot, we should go to the regular hospital in time to identify the cause of the disease, and under the guidance of a professional doctor to choose a suitable method of treatment.