Why do bruises change color?
A bruise changes color because the blood that leaked under the skin is gradually broken down: red then blue-purple in the first 1 or 2 days, green then yellow between day 5 and day 10, and it goes away in about 2 weeks (KidsHealth, 2022). White blood cells called macrophages turn hemoglobin into green, then yellow pigments.
Schematic drawing, not to scale. Dotted curves are estimates, in relative level, based on the timing given by KidsHealth and MedlinePlus; the order of colors varies from person to person.
Why do bruises change color?
A bump, seen in cross-section under the skin, then the two weeks that follow. Choose a situation, then tap a label on the drawing to find out what it is.
Sources: colors and timing (KidsHealth, 2022; MedlinePlus); no yellow before about 18 hours, and earlier under age 65 (Langlois and Gresham, Forensic Sci Int, 1991); dating a bruise (Maguire et al., Arch Dis Child, 2005); biliverdin and bilirubin (StatPearls; Hughes et al., J Clin Pathol, 2004); blood and oxygen measured (Marin et al., Sensors, 2021); older skin (StatPearls, to be verified). Drawing not to scale; durations and sizes in the scene: estimates.
Keyboard: 1 to 3 situations, Space pause, L slow motion, R restart, ← → previous or next step.
Frequently asked questions about bruises
How long does a bruise last?
Most bruises go away in about 2 weeks (KidsHealth; MedlinePlus). A large or deep bruise can last longer: according to MedlinePlus, from a few days to a few months. It usually goes from red to blue-purple in the first 1 or 2 days, to green then yellow between day 5 and day 10, then to yellowish brown before fading between day 10 and day 14 (KidsHealth).
Why does a bruise turn green, then yellow?
Because the hemoglobin in the blood that leaked under the skin is gradually broken down. Cleanup white blood cells, the macrophages, swallow the red blood cells; their enzyme, heme oxygenase, turns heme into biliverdin, a green pigment, then a 2nd enzyme makes it into bilirubin, which is orange-yellow (StatPearls). Bilirubin absorbs blue light, which gives old bruises their yellow (Hughes, 2004). It is then carried away by the blood.
Can you date a bruise by its color?
Not reliably. A review of 167 studies, 3 of which were kept, shows that clinicians dated a bruise within 24 hours less than 4 times out of 10, and could only tell whether it was recent, middle-aged or old 55 to 63 times out of 100 (Maguire, 2005). Only one rule roughly holds: in 369 photos, a yellow bruise was always more than about 18 hours old (Langlois, 1991).
What can you do to make a bruise go away faster?
Right after the bump: ice wrapped in a cloth, never directly on the skin, up to 15 minutes per hour, and the limb raised (MedlinePlus). KidsHealth advises 15 to 20 minutes, 3 or 4 times a day, for 1 or 2 days, and no heat in the first 48 hours. For arnica, there is only one small study, on bruises made with a laser: a 20% ointment did better than petroleum jelly after 2 weeks, but no better than a 5% vitamin K cream (Leu, 2010).
When should a bruise worry you?
It is best to get advice for a bruise that is not better after 2 weeks, very swollen or very painful, near the eye with vision problems, or for frequent bruises for no reason (KidsHealth). Strong pressure in a bruised and very painful limb is an emergency (MedlinePlus). Blood thinners such as aspirin, warfarin, apixaban or clopidogrel make bruising easier: do not stop them without talking to your doctor (MedlinePlus).
True or false?
You can tell how old a bruise is from its color.
False. In a review of 167 studies, clinicians dated a bruise within 24 hours less than 4 times out of 10 (Maguire, 2005). The order of colors varies from one person and one bruise to another.
The yellow of an old bruise comes from the same pigment as jaundice.
True. It is bilirubin, made from hemoglobin by macrophages, by way of biliverdin, which is green (StatPearls). In a bruise, it stays in place for a few days before being carried away by the blood.
You should heat a bruise right away so it goes away faster.
False. In the first 1 or 2 days, cold is what helps: ice in a cloth, 15 to 20 minutes, and no heat in the first 48 hours (KidsHealth).
This page as text
The same information as the charts, to read without animation: for each chart, the values at the main moments, then the notes with their level of evidence.
Why does a bruise go from purple to green, then yellow?
Because the hemoglobin in blood is broken down into pigments: biliverdin, which is green, then bilirubin, which is yellow. Estimated curves, in relative level, for an ordinary bruise in an adult; the order varies from person to person.
| Days after the bump | Red: hemoglobin with oxygen (estimate) (dotted) | Blue-purple: hemoglobin without oxygen (estimate) (dotted) | Green: biliverdin (estimate) (dotted) | Yellow: bilirubin (estimate) (dotted) | Size of the bruise (estimate) (dotted) | What happens |
|---|---|---|---|---|---|---|
| Bump | 100 | 20 | 0 | 0 | 60 | The bump: blood leaks under the skin |
| Day 2 | 18 | 100 | 5 | 5 | 99 | after the bump: most common color, blue-purple (estimate) |
| Day 5 | 1 | 65 | 60 | 41 | 84 | after the bump: most common color, green (estimate) |
| Day 7 | 0 | 35 | 80 | 68 | 70 | after the bump: most common color, green (estimate) |
| Day 10 | 0 | 10 | 33 | 97 | 45 | after the bump: most common color, jaune (estimate) |
| Day 14 | 0 | 0 | 4 | 45 | 12 | after the bump: most common color, almost gone (estimate) |
| Day 21 | 0 | 0 | 0 | 0 | 0 | after the bump: most common color, almost gone (estimate) |
Key points
- Right after: pinkish red (Until day 1, Shown in humans)
A bump crushes small vessels under the skin without cutting it. The blood that leaks out first makes a pink or red spot, which then darkens to dark blue or purple, then turns green, dark yellow and pale yellow. Source: MedlinePlus, « Bruise healing, series : healing, part 2 », medical encyclopedia - Days 1 and 2: blue-purple or black (From day 0.5 to day 4, Shown in humans)
The blood that leaked from the vessels loses its oxygen and darkens. Seen through the skin, the bruise looks blue, purple, sometimes black, 1 to 2 days after the bump. Source: Pitone (reviewer), « Bruises », KidsHealth, Nemours, 2022 - No yellow before about 18 hours (Until day 3, Shown in humans)
In 369 photos of bruises from 89 people aged 10 to 100, a yellow bruise was always more than about 18 hours old. Red, on the other hand, was seen at any age of the bruise. Source: Langlois and Gresham, « The ageing of bruises: a review and study of the colour changes with time », Forensic Sci Int, 1991 - Measured with light (Until day 8, Shown in humans)
In 3 volunteers followed for 16 days, the amount of blood under the skin rose in the first days while its oxygen fell; bilirubin then appeared, and the skin was back to normal in about 2 weeks. Source: Marin et coll., « Noninvasive monitoring of dynamical processes in bruised human skin using diffuse reflectance spectroscopy and pulsed photothermal radiometry », Sensors, 2021 - Green: biliverdin (From day 4 to day 10, Shown in humans)
Cleanup white blood cells, the macrophages, eat the red blood cells. Their enzyme, heme oxygenase, splits the heme in hemoglobin into biliverdin, a green pigment. Source: StatPearls, « Physiology, Bilirubin » - Yellow: bilirubin (From day 5 to day 14, Shown in humans)
A 2nd enzyme turns biliverdin into bilirubin, which is orange-yellow. It gives old bruises their yellow: it absorbs blue light, around 480 to 490 nanometers. Source: Hughes et coll., « The practical application of reflectance spectrophotometry for the demonstration of haemoglobin and its degradation in bruises », J Clin Pathol, 2004 - Gone in about 2 weeks (From day 10, Shown in humans)
Between day 10 and day 14, the bruise turns yellowish brown, then fades. Most bruises go away in about 2 weeks. Source: Pitone (reviewer), « Bruises », KidsHealth, Nemours, 2022 - Dating a bruise by its color: not reliable (Throughout, Shown in humans)
In a review of 167 studies, 3 of which were kept, clinicians dated a bruise within 24 hours less than 4 times out of 10, and could only tell whether it was recent, middle-aged or old 55 to 63 times out of 100. Source: Maguire et coll., « Can you age bruises accurately in children? A systematic review », Arch Dis Child, 2005 - Yellow does not explain everything (Throughout, Shown in humans)
Measured with a device, the yellow of a bruise explained only 13% of the differences in bruise age, and 32% with other factors. Source: Hughes et coll., « Use of reflectance spectrophotometry and colorimetry in a general linear model for the determination of the age of bruises », Forensic Sci Med Pathol, 2010 - Estimated curves (Throughout, Hypothesis)
Colors and size are drawn in relative level, based on the timing given by KidsHealth and MedlinePlus. A real bruise does not always follow this order.
Why do some bruises last longer?
A bruise lasts longer when more blood has leaked under the skin, or when the skin is thin and older. Estimated curves: share of the bruise still visible, day by day.
| Days after the bump | Adult, small bump (estimate) (dotted) | Older skin, on the forearm (estimate) (dotted) | On a blood thinner (estimate) (dotted) | What happens |
|---|---|---|---|---|
| Bump | 100 | 100 | 100 | The bump: blood leaks under the skin |
| Day 2 | 98 | 99 | 100 | after the bump: most common color, blue-purple (estimate) |
| Day 5 | 82 | 93 | 95 | after the bump: most common color, green (estimate) |
| Day 7 | 65 | 85 | 85 | after the bump: most common color, green (estimate) |
| Day 10 | 40 | 69 | 65 | after the bump: most common color, jaune (estimate) |
| Day 14 | 10 | 45 | 35 | after the bump: most common color, almost gone (estimate) |
| Day 21 | 0 | 10 | 5 | after the bump: most common color, almost gone (estimate) |
Key points
- Days to months (Throughout, Shown in humans)
According to MedlinePlus, a bruise can last from a few days to a few months, depending on its size and depth. Source: MedlinePlus, « Bruise », medical encyclopedia, National Library of Medicine - Blood thinners (Throughout, Shown in humans)
Aspirin, warfarin, dabigatran, rivaroxaban, apixaban or clopidogrel make bruising easier. Never stop such a treatment without talking to your doctor. Source: MedlinePlus, « Bruise », medical encyclopedia, National Library of Medicine - Yellow comes sooner before age 65 (Until day 10, Shown in humans)
In the study of 369 bruise photos, yellow appeared sooner in people under 65 than in older people. Source: Langlois and Gresham, « The ageing of bruises: a review and study of the colour changes with time », Forensic Sci Int, 1991 - Thin, older skin (Throughout, Shown in humans)
With age and sun, the skin thins and small vessels are less well supported: large purple patches appear on the forearms and the backs of the hands at the slightest bump. This so-called actinic purpura is said to affect about 12% of people over 50 and 30% of those 75 and older, and each patch lasts up to 3 weeks (to be verified). Source: StatPearls, « Actinic Purpura » - Estimated curves (Throughout, Hypothesis)
No study gives the exact duration of a bruise by age or treatment: these curves only show the direction of the difference, in relative level.
What makes a bruise go away faster?
Cold and raising the limb, right away, limit the blood that leaks out. For arnica, there is only one small study, on bruises made with a laser. Estimated curves: share of the bruise still visible.
| Days after the bump | Nothing (estimate) (dotted) | Cold and limb raised right away (estimate) (dotted) | 20% arnica ointment, twice a day (estimate) (dotted) | What happens |
|---|---|---|---|---|
| Bump | 100 | 80 | 100 | The bump: blood leaks under the skin |
| Day 2 | 98 | 79 | 96 | after the bump: most common color, blue-purple (estimate) |
| Day 5 | 82 | 68 | 76 | after the bump: most common color, green (estimate) |
| Day 7 | 65 | 52 | 58 | after the bump: most common color, green (estimate) |
| Day 10 | 40 | 30 | 33 | after the bump: most common color, jaune (estimate) |
| Day 14 | 10 | 7 | 6 | after the bump: most common color, almost gone (estimate) |
| Day 21 | 0 | 0 | 0 | after the bump: most common color, almost gone (estimate) |
Key points
- Cold, the first 1 or 2 days (Until day 2, Shown in humans)
Ice wrapped in a cloth, 15 to 20 minutes, 3 or 4 times a day, for 1 or 2 days, and no heat in the first 48 hours. MedlinePlus advises up to 15 minutes per hour, never ice directly on the skin. Source: Pitone (reviewer), « Bruises », KidsHealth, Nemours, 2022 - Raise it (Until day 2, Shown in humans)
Keeping the arm or leg higher than the heart helps less blood pool. Source: MedlinePlus, « Bruise », medical encyclopedia, National Library of Medicine - Arnica: one small study (Until day 14, Shown in humans)
On 7 mm laser-made bruises in volunteers, a 20% arnica ointment, twice a day for 2 weeks, did better than petroleum jelly and a 1% vitamin K cream, but no better than a 5% vitamin K cream. The difference was only measured after 2 weeks. Source: Leu et coll., « Accelerated resolution of laser-induced bruising with topical 20% arnica: a rater-blinded randomized controlled trial », Br J Dermatol, 2010 - What we do not know (Throughout, Hypothesis)
No large study says by how many days cold shortens a bruise. The curves only show the direction of the effect. - When to show it to a doctor (From day 14, Shown in humans)
A bruise that is not better after 2 weeks, very swollen and painful, near the eye with vision problems, or frequent bruises for no reason: it is best to get advice. Source: Pitone (reviewer), « Bruises », KidsHealth, Nemours, 2022
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