The most common cause of arm bruises is trauma or a direct impact that leads to bleeding under the skin. This commonly occurs during sports activities, although it can also occur during normal daily activities where a person comes into contact with a solid object. Arm bruises can also be caused by a twisting motion, and are sometimes referred to as an indicator of child abuse in certain situations. If a bruise occurs without impact, some common causes include heart problems and vascular problems. It is best to see a doctor if unexplained bruising occurs.
When an arm is traumatized, blood vessels within the arm can rupture, causing bleeding under the skin. The color of the bruise on your arm is likely to change over time; Initially, the bruise will be dark red or black in color, as the blood under the skin is red. After the bruise on the arm begins to heal, the color can change from black or red to green and even shades of yellow. Eventually, the bruise will completely disappear. Some swelling may also accompany the bruise, and if this swelling or discoloration lasts for more than a few days or weeks, or if the pain worsens, it is advisable to seek medical attention immediately.
Narrowing or hardening of the blood vessels in the arms can also lead to arm bruising. Such bruising as a result of hardening or narrowing of the blood vessels is often a concurrent condition along with high blood pressure, hardening of the arteries, and heart disease. People suffering from these conditions may notice bruising, especially after exercise, and if this occurs, it is advisable to see a doctor immediately for a full diagnosis of what may be causing the bruising on the arm. Some of the problems can be quite serious and may require immediate medical attention.
As people age, the capillaries in the skin tend to weaken and become more sensitive, so arm bruises are likely to occur more often in older people. This is not necessarily something to worry about, although if persistent or mysterious bruising occurs, it is advisable to see a doctor. Women tend to be more susceptible to bruising than men, although this is not the case across the board. Children can also bruise quite easily, especially since children tend to be much more active than adults.