burn, 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.