Causes of sudden nosebleeds in adults include trauma to the nose, picking at the nose or irritation from a cold, according to WebMD. It is also possible to get a sudden nose bleed due to the development of a disease.
Disease is a less common reason for sudden nose bleeds, but conditions such as blood clotting diseases may contribute to bleeding from the nose, explains WebMD. Medications such as warfarin or aspirin may also cause blood to be thinner and not clot as it should. Liver disease can also lead to sudden nose bleeds, as it can cause the blood to thin. Rarer reasons for a sudden nose bleed include cancer in the nose or abnormal blood vessels.
Most nosebleeds are not serious, but there are a few times when an individual may want to contact a doctor, WebMD advises. For instance, if nosebleeds are persistent or if there is bleeding from other parts of the body, including blood in the stool or urine, a person should contact a doctor. It's also best to get medical attention when nosebleeds and bruising occur easily. Those taking blood-thinning drugs, such as warfarin or aspirin, should contact a doctor if nosebleeds become frequent. The same is true for those with kidney or liver disease.