is medically known as an ecchymosis. There are multiple reasons to have a bruise, not the least of which is trauma to the region. If you feel that your bruises are out of proportion to the degree of trauma, I would recommend you have this evaluated by your primary car physician. At the very least I would suggest that you see your primary doctor
to evaluate your dry skin which is known as xerosis.
A bruise represent damage to small blood vessels that allow blood to "leak" into the soft tissue and skin. Therefore it is a natural process to have a bruise with any trauma that damages blood vessels.
However there are some conditions that cause people to bleed very or too easily. The major cause of this condition is if the blood is "too thin." bleeding disorders such as low platelets (the blood cell that helps clot form) of low blood levels of clotting proteins can cause this. Another common condition that can cause this is if the blood vessels are weak... As can be caused by inflammation. This is known as a vasculitis
If you feel that the bruises are out of proportion to the physical trauma, you should see your doctor s there are medical conditions that can cause this. Good luck!