What Is a Bruise? The Science Beneath the Skin

Understand what happens when a bruise changes color

Bruises change color as the body breaks down and recovers hemoglobin from red blood cells.
Bruises change color as the body breaks down and recovers hemoglobin from red blood cells. Lisa Valder / Getty Images

Even if you're not clumsy, you've likely gotten enough bruises to know they undergo some pretty freaky color changes during the healing process. Why do bruises change colors? How can you tell when a bruise isn't healing correctly? Learn about the science of what's going on beneath your skin and get the answers.

What Is a Bruise?

Trauma to your skin, muscles, or other tissues breaks the tiny blood vessels called capillaries.

If the injury is severe enough, the skin tears and the blood spills out, forming a clot and a scab. If you're not cut or stabbed, that blood pools beneath the skin with nowhere to go, forming the discoloration known as a bruise or contusion.

Bruise Colors and the Healing Process

The time it takes for a bruise to heal and the color changes it undergoes follow a predictable pattern. It's so predictable, doctors and forensic scientists can use bruise color to estimate when the injury occurred.

At the instant of the injury, the fresh blood spilled into a bruise and the inflammation response to the injury turns the area bright red with fresh oxygenated blood. If the bruise occurs deep beneath the skin, the red or pink coloring may not be visible, but you'll likely feel pain from swelling.

The blood in a bruise isn't in circulation, so it becomes deoxygenated and darkens. While the blood is not actually blue, the bruise may appear blue because it's viewed through the skin and other tissues.

After the first day or so, the hemoglobin from dead blood cells releases its iron. The bruise darkens from blue to purple or black. Hemoglobin is broken down into biliverdin, a green pigment. Biliverdin, in turn, is converted into the yellow pigment, bilirubin, Bilirubin dissolves, returns to the blood stream, and is filtered by the liver and kidneys.

As bilirubin is absorbed, a bruise fades away until it's gone.

As a bruise heals, it often becomes multicolored. It may even spread, especially downward under the force of gravity. Healing is fastest at the edges of a bruise, slowly working toward the interior. The intensity and hue of bruise colors depends on multiple factors, including the severity of the contusion, its location, and skin color. Bruises on the face or arms typically heal more quickly than bruises on the legs.

This chart outlines the colors you can expect from a bruise, their cause, and when they typically start to appear:

Bruise ColorMoleculeTime
Red or PinkHemoglobin (Oxygenated)Time of Injury
Blue, Purple, BlackHemoglobin (Deoxygenated)Within First Few Hours
Purple or BlackHemoglobin and Iron1 to 5 Days
GreenBiliverdinFew Days to a Few Weeks
Yellow or BrownBilirubinFew Days to Several Weeks

How to Speed the Healing Process

If you don't notice a bruise until after you've gotten it, it's too late to do much about it. However, if you get a bump, taking immediate action can limit the amount of bruising and thus the time it takes to heal.

  1. Apply ice or frozen food to the injured area immediately to reduce bleeding and inflammation. Cold constricts blood vessels, so less blood will flow into the area from broken capillaries and the immune response.
  1. Elevate the area, above the heart, if possible. Again, this limits bleeding and swelling.
  2. For the first 48 hours, avoid activities that may increase swelling, such as hot packs or hot tubs. Drinking alcoholic beverages may also increase swelling.
  3. Compression may decrease swelling. To apply compression, wrap the area with an elastic bandage (e.g., Ace bandage). Don't wrap too tightly or swelling may occur below the bruised area.
  4. While cold helps limit bruise formation, use heat to speed healing. After the first couple of days, apply heat to the bruise for 10 to 20 minutes at a time to improve circulation to the area. This raises the rate of chemical reactions in the area and helps flush away pigments.
  5. After the first couple of days, gently massaging the area can help increase circulation and speed healing.
  1. Natural products that may be applied directly to the bruised area include witch hazel and arnica.
  2. If you're experiencing pain, over-the-counter pain relievers can help.

When to See a Doctor

Bruises from minor injuries typically heal on their own within a week or two. It can take months for a large, deep bruise to heal. However, there are some bruises that should get checked out by a medical professional. See a doctor if:

  • You get bruises for no apparent reason. This can be a symptom of a nutritional deficiency or illness. Bruising easily as a response to injury is not typically indicative of a problem.
  • A bruise worsens instead of getting better. Get help if a bruise continues to swell after the first day or two or if it becomes more painful. This could indicate the area is still bleeding or it is infected or that a hematoma has formed. In some cases, the body walls off a region of blood so that it can't drain and heal.
  • You have bruises around the eyes, to be certain there's no fracture or eye damage.
  • You don't have full use of the injured area. For example, if you can't walk on a bruised ankle or use a bruised wrist without pain, it's possible you have a fracture.
  • You develop a fever, streaks of red appear around the bruise, or the bruise starts to drain fluid. These are signs of an infection.
  • The bruise becomes hard and tender. Although uncommon, heterotopic ossification can occur in which the body deposits calcium at the injury site.

Fast Facts

  • A bruise results from blood released when small vessels are broken.
  • Bruises change colors as part of the healing process. The color is an indication of where you're at in the healing process.
  • Knowing what to expect can help you decide if a bruise is healing normally or whether you should seek medical attention.

References

  • "Harrison's Principles of Internal Medicine. 17th ed. United States: McGraw-Hill Professional, 2008".
  • Liem, Edwin B.; Hollensead, Sandra C.; Joiner, Teresa V.; Sessler, Daniel I. (2006). "Women with Red Hair Report a Slightly Increased Rate of Bruising but Have Normal Coagulation Tests". Anesthesia & Analgesia102 (1): 313–8.