Bleeding in the mouth at night during the day is fine for a number of reasons, generally considered to be related to trauma, gingivitis, periodontitis, and coagulation disorders and other factors, the specific situation is analyzed as follows: 1. Trauma: if you sleep at night when dreaming accidentally damage the oral mucosa tissue, resulting in local blood vessel rupture bleeding, can cause oral bleeding. Generally do not need special treatment, the bleeding caused by this situation is small, can disappear by itself. 2. Gingivitis periodontitis: If the patient usually do not pay attention to oral hygiene, the formation of dental calculus. Continuous growth of calculus may stimulate the gum tissue to cause gingivitis, resulting in edema and congestion of the gums. If you unintentionally touch the gum tissue while sleeping, it may cause bleeding gums, manifested as bleeding in the mouth, and need to visit the doctor for a clear diagnosis and targeted treatment. 3. Coagulation dysfunction: mostly seen in hemophilia, leukemia patients. One of the common manifestations of these patients is a variety of bleeding disorders, therefore, if you unintentionally touch the teeth and gums during sleep, can cause local mucosal bleeding, manifested as oral bleeding. This situation often need to improve the relevant examination before targeted, systematic treatment.