Inflammation is characterized by redness, swelling, and heat. The redness of the skin is due to an increase in blood flow, which leads to an increase in temperature. Fluid accumulates when inflammatory cells release histamine, which causes the small blood vessels in tissue to open and let fluid escape. Pain is caused by chemical signals that are released from damaged or injured tissues. These chemicals activate the sensory receptors in the nerve endings surrounding an area.
All of these processes form part a complex series known as an inflammatory reaction, designed to provide protection against infection or injury by activating a localized immunity response. The inflammatory response helps protect the body from further injury while also healing it by providing extra nutrients, oxygen and molecules for repair.