An abundant supply of tiny blood vessels makes the nose particularly vulnerable to bleeding.
Air moving through the nose can dry and irritate the mucous membranes.
This forms crusts which bleed when removed by rubbing, picking, or blowing the nose. The large majority of nosebleeds are associated with minor injuries to the nose or with common colds . Nosebleeds occur more frequently in the winter when viruses are common and heated indoor air dries out the nostrils. A cooler house and a vaporizer, to return humidity to the air, help many people with frequent nosebleeds. This list is not all inclusive, and the causes are not presented in order of likelihood.