What are the most common causes of excessive bruising?

As we get older, the very tiny blood vessels in the outer layer of skin get more fragile. Easy bruising is almost always related to this. Some drugs make skin more fragile, especially oral corticosteroids (prednisone, dexamethasone, prednisolone are examples). Also aspirin, warfarin (Coumadin), and other medicine that interferes with blood clotting will make the bruises larger and more noticeable. It’s very rare, but vitamin and mineral deficiencies can cause skin bruising.