A hard scab on the scalp that bleeds when you pick it may be caused by folliculitis, seborrheic dermatitis, ringworm of the head and other diseases. 1. Folliculitis: mainly caused by Staphylococcus aureus infection, commonly found in the scalp, face, thighs and other parts of the head. Patients will appear locally to the hair follicle as the center of the red mound pustules, pustules rupture after the crust. If picked out will flow pus and blood. 2. Seborrheic dermatitis: the cause of the disease is related to heredity, Malassezia infection and other factors, mostly seen in the scalp, face, trunk and other parts. Patients will appear local erythema, flaking. When the condition is serious, yellow or brown crusts will appear, and scratching can be accompanied by oozing and erosion. If the patient picks the hard crust on the scalp, bleeding may occur. 3. Tinea capitis: the cause of the disease is mainly related to dermatophyte infection. Patients will have scales, yellow crusts, small pustules and other symptoms on the head. If you pick the hard scabs, it may lead to bleeding symptoms. There are many reasons why there are hard scabs on the scalp that bleed when you pick them, so it is recommended that patients go to a regular hospital to get a clear picture of the cause.