Bruises develop when small blood vessels under the skin tear or rupture, most often from a bump or fall. Blood leaks into tissues under the skin and causes the black-and-blue color. As bruises (contusions) heal, usually within 2 to 4 weeks, they often turn colors, including purplish black, reddish blue, or yellowish green. Sometimes the area of the bruise spreads down the body in the direction of gravity. A bruise on a leg usually will take longer to heal than a bruise on the face or arms.
Most bruises are not a cause for concern and will go away on their own. Home treatment may speed healing and relieve the swelling and soreness that often accompany bruises that are caused by injury. But severe bruising, swelling, and pain that begin within 30 minutes of an injury may mean a more serious problem, such as a severe sprain or fracture.
If you bruise easily, you may not even remember what caused a bruise. Bruising easily does not mean you have a serious health problem, especially if bruising is minimal or only shows up once in a while.
- Older adults often bruise easily from minor injuries, especially injuries to the forearms, hands, legs, and feet. As a person ages, the skin becomes less flexible and thinner because there is less fat under the skin. The cushioning effect of the skin decreases as the fat under the skin decreases. These changes, along with skin damage from exposure to the sun, cause blood vessels to break easily. When blood vessels break, bruising occurs.
- Women bruise more easily than men, especially from minor injuries on the thighs, buttocks, and upper arms.
- A tendency to bruise easily sometimes runs in families.
Occasionally after an injury, blood collects and pools under the skin (hematoma), giving the skin a spongy, rubbery, lumpy feel. A regular bruise is more spread out and may not feel like a firm lump. A hematoma usually is not a cause for concern. It is not the same thing as a blood clot in a vein, and it does not cause blood clots.
Bruises that do not appear to be caused by an accidental injury may be caused by abuse. It is important to consider this possibility, especially if the bruises can't be explained or if the explanations change or do not match the injury. Report this type of bruising and seek help to prevent further abuse.
Blood spots under the skin may be either purpura or petechiae. Purpura might look like bruises, but they are not caused by an injury as most regular bruises are. Petechiae don't look like bruises. They are tiny, flat, red or purple spots in the skin, but they are different than the tiny, flat, red spots or birthmarks (hemangiomas) that are present all the time.
Sudden unexplained bruising or blood spots under the skin or a sudden increase in the frequency of bruising may be caused by:
- A medicine, such as aspirin or blood thinners (anticoagulants).
- Infection that causes the buildup of toxin in the blood or tissues (sepsis).
- A bleeding or clotting disorder, such as hemophilia, von Willebrand's disease, thrombocytopenia, or another less common bleeding or clotting disorder.
- Other diseases that affect clotting. Examples include:
- Inflammation of a blood vessel (vasculitis).
- Malnutrition, such as deficiencies of vitamins B12, C, or K, or folic acid.
Medical treatment for abnormal bruising or blood spots focuses on preventing or stopping bleeding, changing or adjusting a medicine that may be causing the bruising, or treating the medical problem that is causing the bruising.
If the skin is injured over a bruise, be sure to watch for signs of a skin infection.
Check your symptoms to decide if and when you should see a doctor.