If the dermis is destroyed, the nerve endings that allow a person to feel pain, temperature and touch are also destroyed. Tissue damage is not only caused by heat but also toxic mediators of inflammation that are activated after a burn. Although inflammation is required for healing, excess production of mediators will cause more endothelial damage. Inflammation is also caused by surface eschar, bacterial colonization and mechanical trauma. Neutrophils are sent out to attack and kill the bacteria.
Dead cells accumulate and can put pressure on surrounding tissues.
Also with increased neutrophils, there is increased consumption of oxygen from neutrophils. This leaves little oxygen for other tissue. As a result of the burn injury the body releases chemicals that cause fluids to leave the blood vessels. This fluid accumulates in and around the burn causing edema Edema puts pressure on surrounding tissues causing pain. Additionally as burn injuries heal nerves are often trapped in scar tissue resulting in life long pain problems.