A burn is an injury to tissue resulting from heat, chemicals, or electricity.
The severity of a burn depends on the amount of tissue affected and the depth of the injury, which is described as first, second, or third degree.
First-degree burns are the least severe. The burned skin becomes red, painful, very sensitive to the touch, and moist or swollen. The burned area whitens (blanches) when lightly touched, but no blisters develop.
Second-degree burns cause deeper damage. The skin blisters. The base of the blisters may be red or whitish and filled with a clear, thick fluid. The burn is painfully sensitive to the touch and may blanch when touched.
Third-degree burns cause the deepest damage. The surface of the burn may be white and soft or black, charred, and leathery. Because the burned area may be pale, it can be mistaken for normal skin in light-skinned people, but it doesn’t blanch when touched. Damaged red blood cells in the injured area may make the burn bright red. Occasionally, the burned area blisters, and hairs in the burn can easily be pulled from their roots. The burned area has no feeling when touched. Generally, third-degree burns aren’t painful, because the nerve endings in the skin have been destroyed.
Distinguishing between deep second-degree burns and third-degree burns is difficult until days after the injury.
Sunburn results from an overexposure to ultraviolet B (UVB) rays. Depending on the type of skin pigment a person has and the amount of sun exposure, the skin becomes red, swollen, and painful one hour to one day after exposure. Later, blisters may form, and the skin may peel. Some sunburned people develop a fever, chills, and weakness, and those with very bad sunburns even may go into shock–low blood pressure, fainting, and profound weakness.
The first tingling or redness is a signal to get out of the sun quickly. Cold tap water compresses can soothe raw, hot areas, as can lotions or ointments without anesthetics or perfumes that might irritate or sensitize the skin. Corticosteroid tablets can help relieve the inflammation and pain within hours.
Sunburned skin begins healing by itself within several days, but complete healing may take weeks. Sunburned lower legs, particularly sunburned shins, tend to be particularly uncomfortable and slow to heal. Skin surfaces rarely exposed to the sun can get badly sunburned because they contain little pigment. Such areas include the skin normally covered by a bathing suit, the tops of the feet, and the wrist normally protected by a watch.
Sun-damaged skin makes a poor barrier against infection, and if an infection develops, healing may be delayed. A doctor can determine the severity of an infection and prescribe antibiotics if necessary.
After burned skin peels, the newly exposed layers are thin and initially very sensitive to sunlight. These areas may remain extremely sensitive for several weeks.