Bruises turn yellow due to the breakdown of hemoglobin.
Here's a breakdown of the process:
The Bruising Process
When you get a bruise, blood vessels under the skin rupture, leaking blood into the surrounding tissues. This blood initially appears red or dark blue/purple. Over time, the body starts to break down this blood, leading to the color changes we see.
Hemoglobin Degradation and Color Changes
The key to the color change lies in the breakdown of hemoglobin, the oxygen-carrying molecule in red blood cells. As the reference states, "After 5 to 10 days, they may turn yellow or green due to the presence of biliverdin and bilirubin by hemoglobin degradation."
- Initial Colors (Blue, Purple, Black): In the first 1-2 days, the blood loses oxygen, causing the bruise to appear blue, purple, or black.
- Green and Yellow Appearance: As hemoglobin breaks down, it is converted into biliverdin (greenish) and then bilirubin (yellowish). The presence of these compounds gives the bruise its characteristic yellow or green color.
Visual Summary
Stage | Timeframe | Primary Cause | Color(s) |
---|---|---|---|
Initial | 1-2 Days | Blood losing oxygen | Blue, Purple, Black |
Late Stage | 5-10 Days | Hemoglobin degradation to Biliverdin & Bilirubin | Yellow, Green |
In essence, the yellow color of a bruise signals that your body is effectively clearing away the leaked blood and that the healing process is well underway.