Usually due to changes in weather, forced air heat
, or air conditioning use, which dessicates the very thin nasal mucus membranes.
Whendisturbed like during aggressive sneezing, noseblowing, or digital manipulation of the nose, the membranes will bleed. If persistent, it is imperative to have the nose examined for polyps or other tissue abnormalities. High blood pressure can also cause nosebleeds.