After washing your hair at night, use a hair dryer to dry it before going to bed. If you go to bed without blow-drying, wet hair may cause the following effects: First, it may cause scalp skin infections, such as bacterial infections, fungal infections or eczema, because wet hair is conducive to the growth of bacteria or other microorganisms, causing skin infections, this situation requires examination and treatment in the dermatology department of a regular hospital. Secondly, wet hair and low temperature may cause contraction of the scalp, resulting in tension headache or cold symptoms, and it is best to go to the neurology or respiratory medicine department of the hospital for examination and treatment when such symptoms occur. Therefore, it is best to blow dry your hair after washing it at night to avoid adverse consequences.