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Why Do Head Injuries Bleed so Much?

Head injury patient at doctor

Bleeding happens as the result of trauma to a blood vessel. A head injury is any trauma to your scalp, skull, or brain. Head injuries can range in severity from a mild bump on your head to a serious brain injury. Traumatic brain injury (TBI) is a serious type of head injury, according to the Centers for Disease Control and Prevention (CDC), and more than 2 million people go to the emergency department for TBIs every year.

A head injury may be closed or open. A closed head injury is one where something hit you very hard on your head but the object did not break your skull. An open head injury occurs when the object breaks your skull and enters your brain. Both types of head injuries can cause bleeding.

Head injuries can cause internal and external bleeding. Internal bleeding occurs inside the head, while external bleeding spills blood outside of the body through a break in the skin. Internal bleeding from a head injury may cause visible signs, such as a bruise, or cause injuries invisible to the naked eye.

Bleeding associated with head injuries can occur in brain tissues, in the layers surrounding the brain, and from the skin on your scalp. Most bleeding from minor head wounds is not serious, however. When bleeding is restricted to one area, bruising and swelling may appear. Doctors refer to this as a hematoma and, for the most part, a superficial hematoma is not harmful.

But Why Do Head Injuries Bleed So Much?

Head injuries bleed a lot because of all the blood vessels there. Your brain requires a tremendous amount of oxygen to do its job. In fact, about 20 percent of the blood flowing from your heart goes up to your brain. Other organs in your head, such as your eyes, also require a steady supply of oxygen-rich blood to work well.

Arteries transport the oxygen- and nutrient-rich blood from your heart to the rest of your body, including your head. The cells of your body absorb the oxygen and nutrients from the blood to work and function, which causes the cells to create carbon dioxide and other toxins. Veins carry these toxins away from cells and back to the heart and lungs.

Blood vessels in your skin also help regulate your body temperature. Your body increases blood flow to vessels near the surface of the skin to allow heat to escape when you are too hot, and reduces blood flow when you are too cold. Because of their location, these superficial blood vessels are vulnerable to injury associated with trauma.

Your scalp can bleed profusely from even a minor cut. Many tiny arteries and veins serve the individual muscles and skin on your head. Some of these blood vessels lie deep within your skull, while other superficial arteries and veins are quite close to the surface of your skin.

"The scalp is very thick skin, and because of it's extensive blood supply even small lacerations to the head can lead to very large amounts of bleeding," says Troy Madsen, MD, an emergency physician at the University of Utah Hospital.

What to Do for a Bleeding Head Injury

Most head injuries are minor and do not require medical attention, but they sure can bleed a lot. For minor head injuries, treat the wound by holding pressure to stop the bleeding, then wash the wound in the sink or shower. Once the wound is totally clean, you can use an antibiotic ointment to help with the healing process.

"If you can't stop the bleeding by holding pressure, if the edges of the scalp wound are significantly separated, or if the person seems confused, is vomiting, or loses consciousness," says Madsen. "If you've had a head injury you treated at home and experience a headache afterwards, but do not have more serious issues like confusion, vomiting, drowsiness, difficulty with memory or loss of consciousness, you have still experienced a concussion. Rest and make sure there's someone with you to keep an eye on you to watch for any confusion or significant drowsiness—reasons they would want to take you to the ER. Follow up with your doctor for further care of your concussion, and avoid any contact sports or any potential activities which may cause another concussion during at least the next two weeks."

Children with serious head injuries may display the same signs and symptoms as adults but may also cry persistently, refuse to eat, or vomit repeatedly. Infants and small children may develop a collection of blood under the scalp, a "goose egg" that can be a sign of a more serious injury.