Violent nose-blowing, nose-picking, dry nasal mucous membranes, or quite simply a knock on the nose during sport can often be enough to start a nosebleed. Initially the person affected is shocked, but it usually looks much worse than it is. Our nasal mucous membrane consists of many small blood vessels which are referred to as capillaries. These are very easily damaged, but it's rarely necessary to see a doctor because most nosebleeds stop by themselves after a few minutes.
To actively prevent nosebleeds, you should keep the air in the room moist by using a humidifier. People with very sensitive mucous membrane are recommended to treat their nose regularly with a special ointment. If a nosebleed starts despite your best efforts, the usual household remedies are generally effective:
The most important thing is not to swallow the blood. If blood gets into the stomach, the stomach will do its best to get it out again and vomiting will inevitably follow.
If you need a solution fast because you neither have enough time nor a handy ice-pack, there is one more tip. Take a paper handkerchief and tear it down the middle. Then you fold it in such a way that it fits into your mouth and place the folded tissue under your tongue. The bleeding will stop in a few minutes.