You may have noticed that some older people have many bruises on their arms and legs. There are a few reasons this can happen. For one thing older skin is thinner, has less supportive collagen, and less protective fat. But the integrity of tiny blood vessels tends to be weaker with aging, so even bumping into a table, or being hit by a ball your grandchild threw at you can cause blood to leak out into the surrounding tissue, resulting in a bruise. And if you are taking a blood thinner such as aspirin, the ability to clot is compromised, so bruises are more common.