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A burn is damage to the skin. Depending on the type of and severity of the burn, skin may be only superficially damaged, or damage may extend deep within the layers of the skin.

Burns can be caused by extreme heat, extreme cold, chemicals, electricity, or radiant energy (i.e., ultraviolet rays from the sun or an artificial source, and x rays).

The degree of damage of a burn can be classified in two ways. The first, and more traditional way, uses the terms first degree, second degree, and third-degree burns. The second means of classification refers to partial thickness and full thickness burns.

A first-degree burn is one that affects only the uppermost layer of the skin, which is called the epidermis. This type of burn is the most common. Touching a hot stove element or scalding of skin by steam are examples of first-degree burns. Despite the pain associated with these burns, the first-degree burn is the least damaging. Within a few days healing is complete. A first degree burn is also a partial burn.

A second-degree burn extends through the epidermis to the underlying layer of skin, which is called the dermis. Redness and blistering of the skin are characteristics of a second-degree burn. Healing takes longer than with a first-degree burn and some scarring of the healed area might result. A second degree burn is also a partial burn.

A third-degree burn is the most serious type of burn. Here, skin damage extends all the way through the epidermal and dermal layers. These are full thickness burns. The patient may not feel as much pain with these burns, as the nerve endings in the burned area have been destroyed. Skin grafts are usually necessary to repair the damage of third-degree burns, and scarring is routine.

Chemical burns differ from radiant burns in that the skin has no protective mechanism to prevent them. With radiation, the melanin cells spread melanin in the skin to block ultraviolet light from penetrating. With chemical burns no such protective measure exists.

A patient is treated for burn wounds. Photograph by Ken Sherman. Phototake.

Chemical burns can occur with the application of acids, strong alkali (such as lye), or other agents. Some 25,000 industrial chemicals (of about 300,000 in use) can produce chemical burns, either internal or external.

Eyes are also vulnerable to chemical burns. Ideally the worker who is using dangerous materials wears goggles and other protective gear, but the home craftsman may not. Alkalis burn into the eyes rapidly and deeply. Acids burn rapidly, but usually are neutralized by the tears before they burn deeply. Initially, chemical burns may appear to be mild, but during the following day or so the injured tissue may slough off and the extent of the injury will be revealed.

Chemical burns may occur from unexpected sources. Dry cement, for example, because of its lime content, is capable of causing burns if one's skin is exposed to it for hours. Gasoline can penetrate skin and cause a burn after several hours of exposure as well. Never use fuel to clean the hands or use it in any other way that would result in long-term exposure.

Surprisingly, air bags in automobiles have burned some accident victims. The bags inflate explosively upon impact to cushion the car's occupants. However, the gas that inflates the bag is hot when it is released from the cylinder. Several burns from contact with inflating air bags have been reported.

Household chemicals can be as dangerous as industrial ones. Drain openers, for example, are based on lye with other additives and can be responsible for serious burns. Lawn fertilizer should never be handled with bare hands, and any that gets on the skin should be rinsed off immediately. Chemicals present a ready source for both internal and external burns. It is important that these materials be stored out of reach of young people and that they be used with great care. Protective clothing, gloves, and goggles should be worn whenever working with such chemicals. Spills and splashes should be cleaned up immediately and any chemical that contacts the skin should be rinsed off quickly. Excess chemicals or empty containers should be disposed of with care and in accordance with existing regulations. Empty containers should not be saved for reuse.

See also Physiology.



Munster, A. M., and S. Burns. A Family Guide to Medical and Emotional Recovery. Baltimore: Johns Hopkins University Press, 1993.

Wardrope, J., and J. A. Edhouse. The Management of Wounds and Burns (Oxford Handbooks in Emergency Medicine). Oxford: Oxford University Press, 1999.

Wolf, S. E., and D. N. Herdon. Burn Care. Georgetown, TX: Landes Bioscience, 1999.

Brian Hoyle


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—The internal layer of skin lying below the epidermis. It contains the sweat and oil glands, hair follicles, and provides replacement cells for those that are shed from the outer layer.


—The outer layer of the skin consisting of dead cells. It is the primary protective barrier against sunlight, chemicals, and other possible harmful agents. The epidermal cells are constantly being shed and replenished.


—The attachment of skin to an injured area. The new skin, natural or artificial, will prevent the loss of fluids and provide the means for a new, intact layer of skin to form.


—Restoring fluids to the body. Deep and extensive burns allow the escape of fluids needed for proper body functions.

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