What causes nosebleeds? A wide variety of things can act as nosebleed triggers. A nosebleed is one of those common conditions that can have many different causes. Nosebleeds are usually a bothersome condition, but not a terribly serious one.
A nosebleed usually occurs when the septum becomes irritated or injured. The septum is the bony, cartilage covered wall that divides your nose into two nostrils. This wall is filled with blood vessels, so any irritation can easily cause it to bleed. However, any irritation to the inside of the nose, septum or not, can lead to a nosebleed.