If the scalp bleeds yellow water after scratching, there are two possibilities: 1. infection secondary to acute eczema. 2. infection secondary to the acute phase of seborrheic dermatitis. If it is a bacterial infection secondary to acute eczema, the reason is related to allergies, which may be related to genetics, environmental factors, such as baking oil, hair dye, exposure to allergens, their own sensitive body and many other factors, and also related to diet and scalp local application of strong stimulating drugs, treatment can be anti-inflammatory, anti-allergy treatment. If the infection is secondary to the acute phase of seborrheic dermatitis, it may be related to mental factors, dietary habits, vitamin B deficiency, alcoholism and other factors. Both should avoid spicy and irritating food, alcohol, and local water.