A bruise forms when small blood vessels beneath your skin break open and leak blood into the surrounding tissue. This usually happens after a bump, fall, or impact, but the force doesn’t have to be dramatic. Sometimes even mild pressure is enough, especially if other factors make your blood vessels more fragile than usual.
How a Bruise Actually Forms
Your skin is laced with tiny blood vessels called capillaries. When something hits you hard enough, the walls of these capillaries rupture. Blood escapes into the soft tissue beneath your skin, and the red blood cells quickly burst open, releasing hemoglobin, the protein that carries oxygen in your blood. That pool of leaked hemoglobin is what you see as discoloration on the surface.
Your body treats this leaked blood as debris and immediately starts cleaning it up. White blood cells move in to break down the hemoglobin, converting it through a series of pigments. That’s why a bruise doesn’t stay one color. It typically starts red or dark purple (from the fresh hemoglobin), shifts to blue or deep purple as oxygen leaves the hemoglobin, then turns green as the body converts the hemoglobin into a green-tinted pigment, and finally fades to yellow or brown before disappearing. Most bruises heal completely within about two weeks.
Why Some People Bruise More Easily
Not everyone bruises at the same rate from the same impact. Several factors influence how easily your capillaries break and how visible the resulting bruise becomes.
Age: As you get older, your skin thins and loses the layer of fat that cushions blood vessels. The connective tissue in deeper skin layers weakens and can no longer support the tiny blood vessels running through it. This means minor bumps that wouldn’t have left a mark at 30 can cause large, vivid bruises at 70. The medical term for this is actinic purpura, and it’s extremely common on the forearms and hands of older adults.
Sex: Women tend to bruise more easily than men, partly because their skin is generally thinner and has a different distribution of subcutaneous fat.
Skin tone: Bruises are equally common across all skin tones, but they’re more visible on lighter skin. On darker skin, bruises can be harder to spot visually, which sometimes delays recognition of injury.
Medications That Increase Bruising
Several common medications make bruising more likely by interfering with your blood’s ability to clot. Over-the-counter pain relievers like aspirin, ibuprofen, and naproxen all reduce clotting. If you take any of these regularly, even small impacts can produce noticeable bruises.
Prescription blood thinners carry an even higher risk. Anticoagulants such as warfarin, along with anti-platelet medications, directly reduce the blood’s clotting ability, so leaked blood spreads more freely before the body can seal the break. Corticosteroids, whether taken as pills or applied as creams over long periods, thin the skin itself, making the blood vessels underneath more exposed and easier to damage. Some antibiotics, antidepressants, and even dietary supplements like ginkgo biloba can also increase bruising through similar blood-thinning effects.
Nutritional Deficiencies and Bruising
Two vitamins play direct roles in preventing bruises. Vitamin K is essential for producing the clotting factors your blood needs to seal broken vessels. Without enough vitamin K, your clotting factors don’t work properly, and even tiny capillary breaks can bleed more than they should. Vitamin K deficiency is uncommon in people who eat leafy greens regularly, but it can develop in people with certain digestive conditions that impair nutrient absorption.
Vitamin C is necessary for building collagen, the structural protein that strengthens blood vessel walls. When vitamin C levels drop low enough, capillary walls become fragile and break more easily. Severe vitamin C deficiency (scurvy) causes widespread bruising, but even moderate deficiency can make you bruise from lighter impacts than usual.
Bone Bruises Are Different
Not all bruises are skin-deep. A bone bruise, or bone contusion, happens when the impact is forceful enough to damage the bone tissue itself. These injuries feel like a deep, throbbing ache that seems to come from inside the body rather than the surface. You may also notice swelling and skin discoloration over the area.
Bone bruises heal more slowly than soft-tissue bruises. While a typical skin bruise clears up in two weeks, bone bruises can take several weeks to several months to fully resolve. They’re most common after hard falls, sports collisions, or joint injuries, and they often show up alongside sprains or ligament damage.
When Bruising Signals Something Deeper
Most bruises are harmless. But certain patterns can point to an underlying bleeding disorder or other medical condition worth investigating. A bruise larger than 3 centimeters (a little over an inch) that appears without any clear injury is considered clinically significant, especially if you haven’t taken aspirin or similar medications in the prior week.
Other patterns that warrant attention:
- Bruises that don’t match the injury: Large swelling or deep blue areas on the neck, buttocks, or around joints after only minor contact.
- Bruising from multiple sites at once: Bleeding that shows up in two or more unrelated areas of the body suggests a systemic problem rather than a local injury.
- Tiny red or purple dots (petechiae): These pinpoint spots, different from a standard bruise, suggest problems with platelets or blood vessel walls. If they’re raised and tender, a type of blood vessel inflammation may be involved.
- Five or more bruises larger than 1 centimeter in exposed areas: This threshold is one indicator clinicians use to screen for bleeding disorders.
- Unusually heavy periods, prolonged bleeding after dental work, or spontaneous nosebleeds: Any of these alongside easy bruising raises the likelihood of a clotting problem.
Conditions like von Willebrand disease, the most common inherited bleeding disorder, often show up as large bruises without the tiny dot-like spots. Hemophilia tends to cause bleeding into joints and muscles rather than surface bruising. If a bleeding tendency first appears in adulthood rather than childhood, it’s more likely to be an acquired condition, possibly related to liver disease or a medication interaction, rather than something genetic.
In children, unexplained bruising deserves careful attention. An active child with a significant bleeding disorder will almost always have a history of large blood-filled swellings, joint bleeding, or deep muscle bleeding, not just surface bruises. Bruising in unusual patterns, in the shape of objects, or in children who aren’t yet mobile enough to injure themselves raises separate concerns that should be evaluated promptly.