When ice is applied to an injured area, blood clotting occurs. What may be the possible reason behind this?
Blood clotting is the bodies response to injury rather than to application of ice itself.
When tissue is damaged through an injury, it activates fragments in cells such as platelets and proteins in blood plasma to stop the injury from bleeding - forming clots also known as coagulation process.
Another part is, when blood is cold or senses a change in temperature it constricts - this is a part of the homeostatic process in the body wanting to maintain a stable internal environment. For example, if it's cold outside and you go for a walk the body sense's a change in temperature, the blood constricts (vasoconstriction) and prevents warm blood flow to the skin which is why skin looks pale when it is cold. (www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre.../bodytemprev4.shtml)
So, icing of an injury would slow down the inflammatory process/blood flow to the site of the injury (further reducing the extent of bruising etc.,) and this would also be aided by the bodies natural clotting process too.