The symptoms of inflammation, or the inflammatory response, are redness, heat, swelling, and pain. Inflammation is a response to tissue damage caused by injury, irritants, pathogens, distortion or disturbance of cells, and extreme temperatures. There are three stages to the inflammatory response: 1) vasodilation, allowing more blood to flow to the damaged tissue, and increased permeability of the blood vessels; 2) migration of phagocytes to the site of tissue damage; and 3) repair.