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Severity of Burns

The severity of burns is determined by depth. There are three levels of burns: First-degree burns affect only the outer layer of the skin. They cause pain, redness, and swelling. Second-degree (partial thickness) burns affect both the outer and underlying layer of skin. They cause pain, redness, swelling, and blistering. Third-degree (full thickness) burns extend into deeper tissues. They cause white or blackened, charred skin that may be numb. Burns are also classified by size in relation to the entire body. There are formulas used to determine the percentage of the body burned. The table below roughly generalizes the 'rule of nines' for adults where the body is divided into areas equaling multiples of 9% of the body area.

Table: The "Rule of Nines"
Arm: 9% Arm: 9%
Head & Neck: 9% Head & Neck: 18%
Anterior Trunk: 18% Anterior Trunk: 18%
Posterior Trunk: 18% Posterior Trunk: 18%
Leg: 18% Leg: 14%

In an infant or child the 'rule' deviates because of the large surface area of the child's head and the smaller area of lower extremities. The medical team must determine the total area burned in order to determine the amount of replacement fluids needed.