Why a Bruise Changes Colour as It Heals
Most people have pressed a bruise on day three and wondered why it looks worse than it did on day one. The skin has gone from a clean red to something murkier, purple, then a greenish edge, then a yellow wash spreading outward. It looks like deterioration. It is the opposite.
A bruise forms when small blood vessels under the skin, capillaries or slightly larger vessels, break from an impact. Blood leaks into the surrounding tissue. That pooled blood is what you see through the skin. What happens next is a tightly sequenced chemical process that your immune system runs without any input from you, and the colours are its progress report.
The First Colour: Red and Dark Purple
Fresh leaked blood contains haemoglobin carrying oxygen. Oxygenated haemoglobin is bright red. Within hours, that oxygen is consumed by the surrounding tissue, and the haemoglobin becomes deoxygenated, the same colour shift that makes venous blood darker than arterial blood. Through the skin, this reads as deep red moving into purple or violet, sometimes almost black where the bleeding was heaviest. The bruise is at its most visible here, not because it is getting worse, but because the full volume of leaked blood is now sitting just under the surface with no breakdown yet underway.
Why Green Appears Next
The body cannot reabsorb whole haemoglobin. It has to dismantle it. Specialised immune cells called macrophages move into the bruised tissue and begin breaking haemoglobin apart. The first major breakdown product is a compound called biliverdin. Biliverdin is green. This is the same pigment responsible for the greenish colour in old bruises, in certain bird eggshells, and in bile. Its appearance at the bruise's edge, usually starting around day two to four, means the macrophages have begun their work. The green often appears first at the margins of the bruise because those outer areas receive the most immune cell traffic.
The Yellow Stage and What It Means
does not stay as biliverdin for long. An enzyme converts it into bilirubin, which is yellow-orange. Bilirubin is water-soluble, which matters: once haemoglobin has been converted all the way to bilirubin, the body can transport it through the bloodstream to the liver, where it is processed and eventually excreted. The yellow colour spreading across a fading bruise is the moment the breakdown products become small enough to move. A bruise that has gone fully yellow is close to gone, the liver is doing the final clearance. This is also why jaundice, which involves bilirubin building up in the blood when the liver cannot clear it fast enough, turns skin and eyes yellow by exactly the same chemistry.
Why the Sequence Goes Outward
The colour change does not happen uniformly across the bruise. It typically starts at the edges and moves inward, and the centre stays darker longer. This is because the immune cells clearing the debris work from the healthy tissue surrounding the injury inward toward the densest concentration of leaked blood. The centre of a large bruise may still look purple while its edges have already gone green or yellow. Seeing two colours at once on the same bruise is normal and expected, it reflects the geography of the cleanup, not a complication.
When the Timeline Runs Differently
The sequence, red-purple, green, yellow, gone, is consistent, but the pace varies. Skin that is thinner, as it is around the eyes or on the inner forearm, shows colour changes faster because there is less tissue between the blood and the surface. Older skin bruises more easily because the capillary walls are more fragile, and the bruises tend to be larger and slower to clear. Certain medications, including aspirin, warfarin, and other blood thinners, allow more blood to leak from the initial injury and slow the body's ability to form the clot that limits the bruise in the first place, both effects make bruises larger and longer-lasting. A bruise that is still dark purple after ten days, that is growing rather than shrinking, or that appeared without any impact you can recall is worth showing a doctor. The colour sequence itself is reassuring; a bruise that skips it or reverses it is not.
The chemistry running under a bruise is the same chemistry the liver uses every day to process the red blood cells that naturally reach the end of their lifespan. A bruise is simply that process made visible through the skin, compressed into one location, triggered by one event. The colours are not damage. They are evidence of a system working through a problem in the only order it knows how.
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