What happens if you leave blood under your skin? The stages of healing and potential risks

September 28, 2025 •

4 min read

According to the Cleveland Clinic, most minor bruises and hematomas are not serious and will be reabsorbed by the body naturally. So, what happens if you leave blood under your skin? The body initiates a complex, multi-stage healing process to break down and clear the pooled blood.

Quick Summary

If left alone, pooled blood from a minor injury is reabsorbed by the body through a natural, multi-stage healing process, resulting in the bruise's characteristic color changes. However, larger or deeper blood collections known as hematomas can sometimes cause complications and require medical attention.

Key Points

Natural Reabsorption: The body's immune system naturally reabsorbs pooled blood from a bruise or minor hematoma over several weeks through a process that causes color changes.
Color Progression: As a bruise heals, it changes color from red/purple to green, and finally to yellow/brown, reflecting the breakdown of hemoglobin.
Bruise vs. Hematoma: A bruise is a flat patch of discoloration, while a hematoma is a larger, deeper collection of blood that often forms a firm, painful lump.
Watch for Complications: Large hematomas can cause pressure on nerves and tissues, potentially leading to pain, numbness, or, in rare severe cases, tissue damage.
When to See a Doctor: Seek medical attention for unexplained or rapidly growing bruising, severe pain, signs of infection, or if a hematoma is causing nerve-related symptoms.

The Body's Natural Healing Process

When small blood vessels are damaged, they leak blood into the surrounding tissue, causing the discoloration we recognize as a bruise. A hematoma is a more significant collection of pooled blood, often forming a firm, swollen lump. In most cases, the body's immune system will naturally reabsorb this blood over time.

The Stages of Color Change

The familiar progression of a bruise's color is a visual timeline of your body's recovery process:

Reddish/Pink: Immediately after the injury, the bruise appears reddish or pink as fresh, oxygen-rich blood pools under the skin.
Blue/Purple/Black: Within one to two days, the blood loses its oxygen, causing it to turn blue, dark purple, or black.
Green: After about five to ten days, the body begins breaking down hemoglobin into other compounds, causing the bruise to turn green.
Yellowish-Brown: In the final stages, the bruise appears yellowish or brownish before completely fading.

How Long Does Healing Take?

Healing time varies depending on the bruise's size, location, and a person's overall health. Minor bruises typically resolve within two weeks. Larger bruises or hematomas can take a month or longer to fully disappear.

Bruise vs. Hematoma: Understanding the Difference

While often used interchangeably, bruises and hematomas are not the same, and distinguishing them is crucial for knowing when to seek medical help.


Characteristic	Bruise (Ecchymosis)	Hematoma
Appearance	Flat, discolored patch; often small.	Raised, swollen, lumpy mass; larger and deeper.
Feel	Tender to the touch but generally not firm.	Firm, rubbery, or spongy to the touch; often more painful.
Location	Typically shallow, just under the skin.	Can be subcutaneous (under the skin), intramuscular (in muscle), or even internal.
Associated Risks	Rarely serious unless accompanied by other injuries.	Potential for severe complications, especially internal types.

Potential Risks and Complications

While many pooled blood collections are benign, larger or internal hematomas, if ignored, can lead to serious complications. The risk is elevated if the collection puts pressure on surrounding structures, particularly nerves or organs.

Nerve Compression: A large hematoma can press on nearby nerves, causing symptoms such as numbness, tingling, or weakness in the affected area.
Infection: Though rare, a hematoma can become infected, especially if it develops near an open wound or is caused by a medical procedure. An infected hematoma may develop into an abscess, requiring drainage and antibiotics.
Tissue Necrosis: In cases of extremely tense or large hematomas, especially in the extremities, the pressure can compromise the blood supply to the overlying skin or underlying tissues, potentially leading to tissue death (necrosis).
Compartment Syndrome: An urgent medical emergency, this condition occurs when a large hematoma within a confined space (like a muscle compartment) creates so much pressure that it cuts off blood flow to the nerves and muscles.

When to Seek Medical Attention

Most simple bruises do not require a doctor's visit and will heal naturally. However, you should consult a healthcare provider for any of the following:

A bruise or hematoma that is rapidly enlarging.
Intense pain and swelling that worsens over time, not improving after 48 hours.
Bruising that appears without an explanation, especially if you take blood-thinning medications.
A firm, painful lump that persists for several weeks without improvement.
Any signs of infection, such as redness, warmth, fever, or pus.
Bruising accompanied by numbness, weakness, or tingling.
Head injuries causing a change in consciousness, a severe headache, confusion, or vomiting.

At-Home Care for Minor Bruises and Hematomas

For minor, superficial cases, a few simple steps can help manage swelling and discomfort:

Rest: Avoid using the injured body part to prevent further damage and give the body time to heal.
Ice: Apply a cold compress or ice pack wrapped in a towel for 15-20 minutes at a time, several times a day, for the first 24-48 hours. This helps reduce swelling and pain.
Compression: Use a light elastic bandage on the bruised area to help prevent further swelling, but ensure it is not too tight.
Elevation: Elevate the bruised limb above the level of your heart to help reduce swelling.

For more detailed information on the healing stages of a bruise, you can consult the MedlinePlus website.

Conclusion

Leaving blood under your skin, in the form of a minor bruise, is a common occurrence that the body effectively handles on its own through a predictable healing cycle. The discoloration will fade as the pooled blood is reabsorbed. However, it is important to recognize the signs of a larger or more complicated hematoma. Being aware of the distinction between a simple bruise and a potentially serious hematoma, and knowing the red flags for when to seek medical help, is key to ensuring a safe recovery. Early intervention for concerning symptoms can prevent complications and promote better health outcomes.

Frequently Asked Questions

The time it takes for blood under the skin to be reabsorbed depends on the amount of blood and location. Minor bruises typically fade within two weeks, while larger hematomas may take a month or longer to disappear completely.

While most hematomas are reabsorbed by the body, an untreated hematoma can sometimes lead to complications such as fibrosis or calcification, which can result in a permanent hard mass or scarring.

For minor injuries, blood under the skin (a bruise) is usually not a serious concern. However, large, deep, or internal collections of blood (hematomas) can be serious, especially if they put pressure on nerves or organs, and require medical evaluation.

To help a minor bruise heal faster, you can use the R.I.C.E. method: Rest the area, apply Ice for the first 48 hours, use a Compression bandage, and Elevate the limb. Over-the-counter pain relievers can help with discomfort.

A bruise changes color because the body is naturally breaking down the pooled blood. As hemoglobin (the oxygen-carrying protein) is broken down, it creates new compounds like biliverdin and bilirubin, which cause the characteristic green and yellow colors.

A hematoma is a localized collection of blood outside a blood vessel, which can clot. This is different from a blood clot inside a vein (thrombosis). A hematoma does not cause blood clots in veins.

During healing, a bruise often starts with pain and swelling. As it resolves, it may become itchy as the body’s immune system clears away the trapped blood. This is a normal part of recovery.

You should apply ice or a cold compress for the first 24-48 hours. After that initial period, you can switch to a warm compress or heating pad to help increase blood flow and speed up the reabsorption process.