A bruise, medically known as a contusion or ecchymosis, is a common discoloration of the skin. It develops when small blood vessels beneath the skin’s surface are damaged, causing blood to leak into the surrounding tissues. This localized collection of blood, without a break in the overlying skin, creates the visible mark. Bruises often result from everyday impacts or injuries.
The Process of Bruise Formation
Bruises form following blunt force trauma, which causes physical compression or deceleration forces on the body’s soft tissues. This impact damages tiny blood vessels called capillaries, situated just beneath the skin. When these capillaries break, blood leaks into the surrounding tissues.
The trapped blood then pools under the skin, leading to the visible discoloration. This leaked blood can activate nerve endings, potentially causing pain or tenderness. The damaged capillary lining also releases endothelin, a hormone that helps minimize ongoing bleeding by narrowing the blood vessel.
Common Triggers and Contributing Factors
Blunt force trauma, such as bumps or falls, is the most common cause of bruising. However, several factors can increase an individual’s susceptibility. Aging skin tends to be thinner and loses some of its protective fatty layer, making blood vessels more fragile and prone to damage from minor impacts.
Certain medications interfere with the body’s clotting ability, leading to easier bruising. These include blood thinners (like warfarin and heparin), antiplatelet agents (such as aspirin), and nonsteroidal anti-inflammatory drugs (NSAIDs). Corticosteroids, particularly topical forms, can also thin the skin, increasing bruising risk.
Underlying medical conditions also contribute to increased bruising. Bleeding disorders, such as hemophilia or von Willebrand disease, impair the blood’s ability to clot effectively. Conditions like liver disease or a low blood platelet count (thrombocytopenia) can also make individuals more prone to bruising. Additionally, deficiencies in certain vitamins, notably vitamin C and vitamin K, can weaken blood vessels or slow clotting.
The Healing Journey: Color Changes and Resolution
A bruise undergoes a series of characteristic color changes as the body repairs damaged tissue. Initially, a fresh bruise may appear reddish or purplish due to oxygen-rich blood under the skin. Within a day or two, as the blood loses oxygen, the bruise turns blue or even black.
Over the next five to ten days, the bruise progresses to shades of green or yellow. This color transformation occurs as hemoglobin breaks down into different pigments. Hemoglobin is first converted into biliverdin, which has a green hue, and then further broken down into bilirubin, responsible for the yellow color. Finally, the bruise may appear light brown before fading completely as the body reabsorbs these pigments. Most bruises resolve within one to two weeks, though larger or deeper bruises may take longer to heal.
When to Seek Medical Advice
While most bruises are harmless and heal on their own, certain situations warrant medical attention. Consult a healthcare provider if a bruise is unusually large, causes severe pain, or is accompanied by significant swelling. Bruising that appears without a clear injury or impact, particularly on the trunk, head, or face, should also be evaluated.
Medical advice is also recommended if bruising occurs alongside other symptoms, such as fever, unexplained bleeding elsewhere (like nosebleeds or blood in urine/stool), or numbness or weakness in the bruised limb. If a bruise does not show signs of improvement or fade within two weeks, or if new, unexplained bruises appear frequently, a doctor’s visit is appropriate. Any bruising around the eyes that affects vision or on the head or neck following an injury should prompt immediate medical evaluation.