Nosebleeds are often caused by nasal injury, nasal mucous membrane dryness, nasal inflammation and stimulation of undesirable physical and chemical factors, etc. Smoke after smoking contains nicotine, carbon monoxide and tar and other ingredients, which stimulate the sensitive and fragile mucous membrane of the nasal cavity, causing nosebleeds, but each person reacts differently to this stimulus, and whether or not it bleeds varies from person to person. 1. Nasal injury: Nosebleeds are usually caused by physical or traumatic injury to the nose, which can rupture the internal blood vessels and cause bleeding. 2. Dry nasal mucosa: dry air or dry rhinitis can make the nasal mucosa not moist enough, and then the blood vessels also become fragile, easy to rupture and bleed. 3. Nasal inflammation: bleeding from rhinitis is mainly caused by repeated stimulation of nasal mucosa by pathogenic bacteria. 4. Other causes: such as nasal polyps, nasal septum abnormalities, nasal tumor factors, systemic diseases such as hypertension, heart disease, pulmonary edema, acute infectious diseases are also related to blood disorders, poisoning of certain drugs and chemicals can lead to nose bleeding. 5. Smoking: nicotine, carbon monoxide and tar contained in smoke and other components can stimulate the inflammatory reaction of the nasal mucosa, resulting in expansion of nasal capillaries, brittle, mucosal edema after rupture tendency. In summary, nosebleeds are the result of a variety of causes, whether smoking nosebleeds and the environment and their own factors are closely related, it is recommended to quit smoking to reduce the possibility of causing nosebleeds.