Answer:
A bruise occurs when small capillaries under the skin rupture and blood leaks out. It is usually due to trauma but it is common for some people to "bruise easily" or find bruises and not even remember any trauma causing it.
People with fair skin, older folks, and thin people without much subcutaneous fat will bruise more easily. Like so many variations we see in humans, it is all in your genes. Sudden onset of bruising can be the sign of a blood disorder like leukemia, thrombocytopenia (low platelets) or alcoholism, but other symptoms would also be present.
Talk with your doctor about your bruising and see what explanation fits for you. Since it has been going on since childhood, it is likely to be a manifestation of your individuality.
People with fair skin, older folks, and thin people without much subcutaneous fat will bruise more easily. Like so many variations we see in humans, it is all in your genes. Sudden onset of bruising can be the sign of a blood disorder like leukemia, thrombocytopenia (low platelets) or alcoholism, but other symptoms would also be present.
Talk with your doctor about your bruising and see what explanation fits for you. Since it has been going on since childhood, it is likely to be a manifestation of your individuality.