Blue marks on the skin, which are usually flat and without problems. If there are major injuries (blows, falls, accidents) there may be swelling and pain at the same time. As some days the colors change from blue-purple to more green and then yellow before disappearing after 1-2 weeks. Bruises are naturally most easily seen in those with fair skin.
Bruises are caused by blood leaking from the blood vessels and remaining in the tissue. It is the hemoglobin in the blood that gives the characteristic colour. Hemoglobin without oxygen is blue. Sometimes bruises can be an expression of an underlying disease. Some medicines make you bruise more easily. In the case of new bruises and possibly other ailments at the same time (for example fever, confusion, feeling sick), you should consider seeing a doctor or emergency room. If it bleeds from a skin change, this can be an expression of many different skin diseases, including skin cancer.
Usually no treatment is needed as bruises disappear on their own. In case of skin damage, cooling can relieve. The underlying cause of bruising and tendency to bleed must be investigated.