Common causes of nosebleeds when children wake up from sleep include: indoor environmental discomfort, allergic rhinitis, nasal polyps and so on. 1. Indoor environmental discomfort: If the indoor temperature is too high or too dry, coupled with the child does not like to drink water, it is very easy to cause the body to lack of water when the child sleeps, resulting in nasal mucosa dryness, nasal capillary rupture, and then appear in the morning woke up nosebleed. 2. Allergic rhinitis: If the child himself is allergic, when indoor allergens exist, inhaled while sleeping, it is easy to produce stimulation of the nasal mucosa, resulting in the morning get up runny nose, sneezing, itchy nose and so on, if the nasal mucous membrane is broken, there will be a nosebleed after waking up. 3. Nasal polyps: due to nasal polyp tissue is relatively fragile, when waking up to inhale cooler air or other external stimuli, it is easy to cause polyp tissue rupture bleeding, nosebleed after waking up. All in all, the child woke up with nosebleeds have physiological causes and pathological causes, such as symptoms of discomfort in time to consult a doctor, and for the cause of the treatment.