Burns are contact injuries resulting from exposure to heat, electricity, radiation (mainly solar radiation), or caustic chemicals. They most often involve the skin, but swallowing caustic chemicals can burn the cells lining the inner surface of the esophagus.
The severity of a burn is indicated by its degree. First-degree burns damage only the epidermis, or outermost skin layer; the symptoms are redness, mild swelling, and stinging pain. Second-degree burns penetrate to the dermis, or second skin layer; they appear red or mottled, are more painful, and may be wet because of seepage of tissue fluids through the damaged skin. Third-degree burns destroy all skin down to the fatty layer, and the skin appears white or charred. Such burns may actually feel less painful than second-degree burns because nerve endings are destroyed. In adults, second-degree burns affecting 15 percent of the body are considered a cause for hospitalization; in children the figure is 10 percent.
First aid for burns requires cooling by plain cold water; ice may induce shock. After this an ointment may help to soothe a minor burn, but ointments or greasy substances should never be applied to serious burns. For chemical burns, cool water should be run over the area until all of the chemical is removed. Recovery of persons with severe burns has improved greatly in recent years, following recognition of the special treatment needs of victims and the establishment of regional burn-treatment centers. Early replacement of tissue fluids has become routine at these centers, along with intravenous nutritional support.
Infections account for a large percentage of the deaths among burn patients, because of injury to the immune system and because the skin is the first line of defense against pathogenic organisms. Burn patients are guarded against infections by being kept in sterile wards and by aggressive treatment with antibiotics; wounds are also closed by grafting as soon as possible after the burn.
Currently, burned areas eventually must be covered by grafts of the patient's own skin, sometimes first stretching the grafts. Temporary grafts from other humans or from pigs can be used as well, and epidermal skin has also been cloned into sheets. An artificial skin being tested in the late 1980s consists of a synthetic epidermis called Silastic and a dermal layer of collagen and a cartilage derivative. The latter serves as a permanent scaffolding for dermal regrowth, while the Silastic is later replaced by grafts. In animal experiments, seeding of the artificial dermis with epidermal cells apparently causes a whole new skin to regenerate on the muscle substrate, so use of the artificial skin could become a one-time operation.