There is red blood at the mouth of the nostril. Patients are advised to go to the ENT clinic for nasal endoscopy to check the situation of each nasal tract in the nasal cavity, and also if the condition requires, it is recommended to do sinus CT or MRI to assist in the examination. Routinely, there may be the following diseases, and the treatment for each disease is different. The first one is more common and may be the erosion and ulceration of the mucous membrane of the nasal cavity, resulting in localized bleeding, which may not bleed a lot and therefore manifest as blood coming out of the nostrils. In this case, you can ask your doctor to prescribe compound menthol nasal drops or use recombinant bovine basic fibroblast growth factor gel to apply to the nasal cavity to promote the healing of the erosion and reduce the possibility of blood leakage. The second condition is the growth of something inside the nasal cavity, such as nasal inversion papilloma, nasal maxillary sinus cancer or septal sinus cancer, olfactory neuroblastoma and other tumors, which may show a small amount of blood and other manifestations when these tumors have localized rupture or invade the surrounding structures. In this case, local biopsy can be performed first to obtain pathology, and based on the pathology results, different surgeries or other radiotherapy treatments can be chosen.