Nosebleeds in children at night may be caused by physical factors, allergies, poor blood clotting function, tumors and other diseases. 1. Physical factors: if the room is dry, children often pick their noses before going to bed, which can cause damage to the mucous membrane of the nasal cavity and bleeding, so it is necessary to ensure that the indoor temperature and humidity are appropriate, and avoid letting children often pick and scratch their nostrils. 2. Allergy: If the environmental conditions are poor, there are allergenic substances, which can lead to the emergence of allergic rhinitis, thus causing the nasal mucosa red, swollen and bleeding. 3. Poor coagulation function: if the child has coagulation disorder and thrombocytopenia, it can appear bleeding from the fragile wall of the nasal cavity, which needs to be clarified by blood test. 4. Tumor: Nasopharyngeal cancer and other malignant diseases can cause nosebleed phenomenon, need to further improve the cranial CT and nuclear magnetic examination to clarify the diagnosis. Children with nosebleeds at night, if repeated episodes, it is recommended to actively seek medical treatment, to clarify the cause of the disease and active treatment.