redness, heat, swelling, and pain are the cardinal signs of inflammation. redness and local heat are both caused by vasodilation of arterioles, which increases the flow of blood to the affected area. swelling is due to the release of histamine and other chemical mediators of inflammation, which increase capillary permeability. this increased permeability allows proteins to leave into the ISF, increasing the ISF osmotic pressure and drawing more fluid out of blood vessels and into the tissues, thereby causing swelling. pain is due to the actions of kinins and prostaglandins on nerve ending, and the swelling which can compress nerve endings