burn, injury resulting from exposure to heat, electricity, radiation, or caustic chemicals. Three degrees of burn are commonly recognized. In first-degree burns the outer layer of skin, called epidermis, becomes red, sensitive to the touch, and often swollen. Medical attention is not required but application of an ointment may relieve the pain. Second-degree burns are characterized by the variable destruction of epidermis and the formation of blisters; nerve endings may be exposed. The more serious cases should be seen by a physician and care should be taken to avoid infection. Local therapy includes application of a chemical such as silver nitrate to produce a soft crust, reduce the threat of infection, and relieve the pain. Third-degree burns involve destruction of the entire thickness of skin and the underlying connective tissue. In the more severe cases underlying bones are also charred. The surface area involved is more significant than the depth of the burn. Shock must be prevented or counteracted; blood transfusion may be required to replace lost body fluids. Invasion of various bacteria must be prevented or cured by administering antibiotics and other drugs. Morphine may be employed to ease pain. Long-term treatment may include transplantation of natural or artificial skin grafts.

Damage caused to the body by contact with flames, hot substances, some chemicals, radiation (including sunlight), or electricity. Burns are classified by depth of skin damage and by percentage of skin damaged. First-degree burns injure only the epidermis (top layer), with redness, pain, and minimal edema. In a second-degree burn, damage extends into the dermis (inner layer), with redness and blisters. Third-degree burns destroy the entire thickness of the skin. There is no pain, because the skin's pain receptors are destroyed. Burns deeper than the skin can release toxic materials into the bloodstream and may require amputation. Secondary shock follows severe burns, caused by loss of fluid both in the destroyed tissue and in leaks from the damaged area. Treatment depends on severity; first-degree burns need only first aid; third-degree burns require long-term hospitalization. Depending on the type, extent, and site of the burn, it may be left exposed, covered with a bandage, or excised to remove dead tissue in preparation for skin grafts. Complications of burns include respiratory problems, infection, ulcers in the stomach or duodenum, and, especially in brown skin, thick scarring. Seizures and hypertension after burns occur almost entirely in children. Survivors usually require plastic surgery, long-term physical therapy, and psychotherapy.

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