A bruise can start out red or purplish, become blue or nearly black, then turn green, yellow, or brown before gradually disappearing. Those color changes are a normal part of the body’s process of breaking down and clearing blood that has leaked into the tissues.
The color does not come from the bruise itself changing in some mysterious way. It reflects changes in the blood pigments left behind after small blood vessels are damaged.
What causes a bruise in the first place?
A bruise, medically called an ecchymosis, forms when small blood vessels beneath the skin are damaged, usually by a bump, pressure, fall, or other minor injury. The vessels may break without causing a cut in the skin, allowing blood to escape into the surrounding tissue.
Because the blood remains trapped under intact skin, it becomes visible as a patch of discoloration. At first, the leaked blood contains large amounts of hemoglobin, the iron-containing protein in red blood cells that carries oxygen. Hemoglobin gives fresh blood its familiar red color.
The appearance of a new bruise can vary depending on its depth, the person’s skin tone, the amount of bleeding, and the lighting. A deeper bruise may initially look dark red, purple, or blue rather than bright red.
Why does a bruise become darker?
As blood sits in the tissue, red blood cells begin to break down. Their hemoglobin no longer behaves exactly as it does inside intact red blood cells, and the changing chemical environment contributes to the bruise becoming darker.
A bruise often appears blue, purple, or very dark during this stage. Part of that appearance is also an optical effect: blood pigments are beneath the surface of the skin rather than exposed directly to view, so the color seen through skin is different from the color of blood outside the body.
The timing is not exact. A bruise can look different from one person to another, and its appearance may change even within the same day.
Where do the green and yellow colors come from?
The most distinctive color changes happen as the body dismantles the hemoglobin left in the injured tissue.
Specialized cells, particularly macrophages, help remove damaged blood cells and their contents. Hemoglobin is broken down into several products during this cleanup process.
One important product is biliverdin, a green pigment. As biliverdin is further processed, it contributes to the formation of bilirubin, a yellow pigment. These pigments help explain why an older bruise may develop green and yellow areas.
Eventually, the pigments and other cellular debris are carried away and processed by the body’s normal waste-removal systems. As less pigment remains in the tissue, the discoloration fades.
The familiar sequence is therefore roughly:
| Stage of healing | Common appearance | What is happening |
|---|---|---|
| Early | Red, reddish-purple, or purple | Blood has recently leaked from damaged vessels |
| Developing | Blue, purple, or dark | Red blood cells and hemoglobin are breaking down |
| Later | Green | Biliverdin and other breakdown products are present |
| Late | Yellow, yellow-brown, or brown | Bilirubin and remaining pigments are being cleared |
| Resolution | Returning toward normal skin color | Pigments and cellular debris have largely been removed |
This sequence is a useful general pattern, not a strict timetable. Bruises do not necessarily pass through every color, and different parts of the same bruise can be at different stages of healing.
How long does a bruise usually take to heal?
Most ordinary bruises gradually fade over about two weeks, although some disappear sooner and others remain visible longer. Larger or deeper bruises can take several weeks to resolve.
The location also matters. Blood can move through tissue after an injury, so discoloration may spread or appear in a nearby area as the bruise evolves. A bruise on a leg, for example, may become more noticeable lower down as blood and fluid shift with gravity.
The fact that a bruise changes shape or seems to move does not necessarily mean the injury is getting worse. What matters is the overall pattern: an uncomplicated bruise should generally become less painful and less prominent as it heals.
Why do bruises sometimes look different on different skin tones?
The underlying biological process is the same, but the visible color can differ substantially.
On lighter skin, bruises may show a progression from red or purple toward blue, green, yellow, and brown relatively clearly. On darker skin, some of these color changes may be less visually distinct, and a bruise may appear deep red, purple, brown, or nearly black.
This is important because the absence of an obvious color change does not mean there is no bruising. Swelling, tenderness, and a change in the texture or appearance of the skin can also signal an injury.
Why can a bruise appear without a memorable injury?
Minor bumps happen constantly, and many are not memorable enough to identify as the cause of a bruise. Some people also bruise more easily because of factors such as age, medications, or differences in the structure and support of the skin and small blood vessels.
As people get older, the skin generally becomes thinner and loses some of the protective tissue around small blood vessels. This can make bruising easier, particularly on areas such as the hands and forearms.
Certain medications can also increase bruising. Blood-thinning medicines and drugs that affect platelet function can make it easier for small amounts of bleeding to produce a visible bruise. Some other medicines can have similar effects indirectly.
Occasional unexplained bruises are often harmless. Frequent, unusually large, or unexplained bruising, however, can sometimes point to a problem with blood clotting, platelets, blood vessels, nutrition, or another underlying condition and deserves medical attention.
Does the color tell you exactly when the bruise happened?
No. Bruise color is not a reliable clock.
Although certain colors tend to occur at particular stages of healing, the progression varies considerably. The depth of the bleeding, amount of blood, location, skin tone, individual healing, and other factors all influence appearance.
For that reason, it is not possible to determine precisely when an injury occurred simply by looking at the color of a bruise.
When should a bruise be checked by a doctor?
A typical minor bruise gradually improves. It becomes less tender, its discoloration fades, and normal skin appearance returns.
Medical evaluation is more appropriate when a bruise is unusually large or painful, keeps getting larger, appears frequently without an obvious cause, or does not seem to be healing. Bruising accompanied by other unusual bleeding—such as frequent nosebleeds, bleeding gums, unusually heavy menstrual bleeding, or blood in urine or stool—also warrants attention.
A bruise that develops after a significant injury should be considered in the context of the injury itself. Severe pain, substantial swelling, numbness, weakness, difficulty moving the affected area, or other concerning symptoms may indicate damage beyond a simple superficial bruise.
A bruise’s changing colors are usually a reassuring sign of normal cleanup: the body is dismantling leaked blood, recycling what it can, and removing the remaining pigments. The progression from red or purple to darker shades and eventually to green and yellow is essentially a visible record of that biological process.
