Although these occur as temperatures begin to plummet, it's not really the low temperature but the absence of moisture in the air that's responsible. This is especially true of inside air that's been warmed by a heater. Although warm air feels nice and toasty, it has also had most of its moisture removed -- that's what causes nosebleeds.

Most winter nosebleeds -- the medical term for nosebleed is epistaxis -- occur from the tiny capillaries in the mucous membrane of the septum, the tough cartilage that divides the nose into two nostrils. When the air is robbed of its moisture by heaters or by climatic forces, this membrane dries out and is easily cracked, which causes breaks in the little capillaries through which small amounts of blood begin to seep.

Bleeding is usually limited because these capillaries are so small that they don't carry a lot of blood. Such nosebleeds are also typically easy to control, simply by applying direct pressure to the bleeding nostril. In more stubborn cases, the application of cold compresses to the nasal area may be required.

On the whole, winter nosebleeds caused by dry air are seldom serious.

Although it's possible to gain temporary relief from dryness in the nose with creams or petroleum jelly, they're seldom a good long-term solution because they don't replace the lost moisture that's drying out the nasal membrane. Medicated nose sprays aren't a good idea either, because they tend to make the dryness worse. Nasal sprays that use water or a mild salt solution, however, often do accomplish the needed moisturizing of the nasal membranes, as do mechanical devices such as vaporizers that add moisture to the indoor air.

More information

There's more to know about nosebleeds from the National Library of Medicine of at The National Institutes of Health.