The medical term for nose bleeding is Epistaxis. A nosebleed typically involves only one nostril and the bleeding can be minor or excessive. There are small blood vessels in your nose that can rupture and bleed easily. The nose most commonly bleeds from the front of your septum, which is the tissue between the sides of your nose. Usually you can stop the bleeding yourself by pinching your nostrils together and keeping your head above your heart.
Temperature and Humidity
Nosebleeds are more common in the winter, because the air is very cold and dry. Warmer temperatures with very low humidity are also conducive to nosebleeds, and presumably you keep your house warm in the winter. This means that during the winter you may be breathing cold, dry air outside and warm, dry air inside. As a result you may experience more nosebleeds during this season.
Certain medications, such as blood thinners or aspirin, can cause nosebleeds. The purpose of blood thinners is to reduce the risk of blood clots and as a result they can cause excessive bleeding. Aspirin also interferes with blood clotting. Using decongestant nasal spray too often can irritate the lining of your nasal passages and cause a nosebleed.
Allergies can result in nosebleeds due to irritation and itching of your nasal passages as well as constantly sneezing and blowing your nose. All of this activity can dry out the lining of your nose, which can cause it to bleed.
Your nose may bleed due to injury, such as being hit in the nose or picking it. If you believe your nose is broken you need to seek medical treatment. In picking your nose you can accidentally damage the membranes inside your nostrils by scratching your fingernail across them, causing bleeding.
Upper Respiratory Infection
An upper respiratory infection will irritate your sinuses as well as your nasal passages. The combination of a runny nose, sneezing and blowing your nose can lead to your nasal membranes becoming sore. If this happens to occur during winter, you are also breathing very dry air, making you more susceptible to a nosebleed.
Lubricating your nose with petroleum jelly or using saline nasal sprays can help prevent nosebleeds, as keeping your nasal passages moist lessens the chance of a nosebleed. You may also try keeping your home at a cooler temperature and using a vaporiser or humidifier if you are prone to nosebleeds.
You should seek emergency medical care if your nose continues to bleed for more than 20 minutes, or if it is the result of a head injury. With continued bleeding, you may need to have the blood vessels in your nose cauterised. A head injury could indicate a fracture to your skull.