They usually result from blows to the skin or a fall.
Bruises can also occur after blood is drawn, or after injections, or shots are given.
Bruises can be small or large, tender to touch, and associated with swelling in the area, depending on how severe the blow, fall, or injury to the skin. There are things one can do at home to treat bruises. Cold packs should be applied to the area in the first 48 hours after an injury, to help constrict the blood vessels and reduce swelling. The sooner the cold pack is applied, the less bleeding will result. A cold pack can be made by putting ice in a plastic bag, covering the bag with a wash cloth or small towel, and applying to the skin.