A burn is damage to an area of the body, internal or external, resulting from application of excess heat, overexposure to sunlight or other radiation, or contact with a caustic chemical. A burn can be a minor, hardly noticeable irritation or it can be of such severity as to be life threatening. Burns are classified as first-, second-, or third-degree (now called full-thickness) depending upon the depth of the burn and damage to the tissue. A full-thickness burn is a severe burn.

The skin

To understand burns and their severity, one must first explore the functions of the skin. The skin is the largest organ of the body. It covers the outer surface and serves multiple purposes.

Its primary function is that of protection. The skin prevents bacteria, dirt, and other foreign materials from getting into the body and initiating an infection. Probably trillions of bacterial cellsrest on the human skin at any one time. Cutting or puncturing the skin offers bacteria and viruses an entry into the area of the body that is most hospitable to them. An intact skin is the outermost defense against this occurrence.

The skin is far more than simply a dry envelope, however. It aids in regulating the body temperature by sweating. The inner layer of the skin contains sweat and oil glands that discharge their products through pores in the outer skin. The oil keeps skin supple and the sweat aids in ridding the body of waste products and also, on hot days, helps to cool the internal temperature. Evaporation of the sweat cools the skin surface.

Beneath the skin the body fluids circulate between and in and out of the cells. Blood, serum, lymph, water, and other materials can move from place to place because the outer skin prevents their loss. Destruction of wide areas of the outer skin, as occurs in full-thickness burns, however, allows the body fluids to drain and evaporate at a great rate. If the burn is extensive enough the loss of fluids can become critical.

First-degree burns

A first-degree burn is the mildest burn and seldom poses any problem other than an irritation. A mild sunburn or a small burn received by touching a hot pan are examples of first-degree burns. The affected area of skin turns a darker color. No blisters are evident and the skin is not broken.

An extensive sunburn, affecting the entire back, back of the legs and arms, and back of the neck, while widespread, still is a first-degree burn. It will be tender to touch, irritated and by clothing, but it poses no hazard and usually will not require medical attention. Application of a soothing antisunburn agent available at most drugstores will dampen the heat and ease the area back to normalcy.

A sunburn is the reaction of the skin to ultraviolet light rays of a wavelength of about 3,000 angstroms. Skin reaction will be apparent in one to 24 hours, and even the most severe reactions will peak in about 72 hours. However, after such a sunburn the skin will be more susceptible to another such burn because the original sunburn resulted in skin cells being shed and some protection lost. A subsequent sunburn may be much more severe than the first one because of the newly exposed underlayer of skin. Fair-skinned individuals will not tan, but will shed the outer layer of skin. These individuals are especially susceptible to sunburn and should stay out of the Sun or well wrapped.

Second-degree burns

A slightly more severe condition than first-degree burns, the appearance of blisters on the skin indicates that the burn is second degree. The burn damage extends through the outer layer of the skin to the underlying dermis. Vesicles or blisters form, indicating the loss of fluid from the cells.

Second-degree burns are more painful and slower to heal, but not significantly, than lighter burns. The damage does not interfere with replacement of lost skin cells and the pain can be relieved by over-the-counter burn relief medications. Extensive second-degree burns may result in lost work time because tight clothing can break the blisters and irritate the underlying raw tissue. Loose, nonbinding clothing is necessary if one has a second-degree burn on the trunk or legs.

Again, the skin is more susceptible to another burn if the original burn was the result of overexposure to sunlight. Some of the protective outer layer of skin cells have been sloughed off and the inner layer, not yet hardened, burns easily.

Touching the hand or other part of the body to a hot object or having hot embers contact the skin also can result in second-degree burns. The result is the same as if sunburn had caused the lesion: the skin changes color and fluid leaks from between the cells under the skin and forms liquid-filled blisters on the surface of the skin. It is best that the blisters be punctured and drained from a pinhole than to wear chafing clothing over them that will rub off the entire skin surface. If need be a light bandage can be placed over the burned area to protect it.

Full-thickness burns

Third-degree, or full-thickness burns are the most severe. Sunburns are never so advanced. The burn damage includes destruction of the epidermis and dermis and possibly underlying tissue. At first, these burns may be difficult to distinguish from second-degree burns because blisters may form early, but they soon will slough off and the area of tissue destruction will become evident.

A more serious category of full-thickness burns, called fourth-degree burns, are those that penetrate the skin and burn into the underlying muscles and perhaps even into bones. Such burns will require extensive therapy, grafts, and rebuilding of the affected tissues as well as follow-up physical therapy to restore full function to the affected limb. Burns of this severity can result in loss of function of an extremity because muscle and nerve are destroyed.

Such burns result most often from the direct exposure of skin to open flame or very hot substances such as molten metal. Tissue destruction can be deep and, if widespread, dangerous. A full-thickness burn, even a very localized one, will require medical attention because of the distinct possibility that an infection will develop in the burned area. In addition, a widespread full-thickness burn allows the escape of fluid from the burn area and may result in dehydration of the patient. Special measures may need to be applied to hydrate the burned person.

These burns often require skin transplants to cover the burn area. The depth of the burn allows blood and fluid to escape and also provides a very easy route for invasion of infectious agents. If left unattended, the burn area may start to heal from the edges and formation of scar tissue will result. This will draw the wound area together in a taut and painful scar that may interfere with normal function of a hand, for example. Skin grafting prevents such a result and allows the area to heal in a way that will preserve function.

Third- and fourth-degree burns, if they involve a large enough area of the body, are life threatening. Someone who has suffered a third-degree burn over, say, 50% of his body is facing a long and painful course of recovery that must be carefully monitored to prevent secondary infections. The loss of fluid through such a widespread area of damage may be more rapid than the fluid can be replaced. Surprisingly, there is usually little pain with such burns because the nerve endings have been burned away with the tissue. The pain involved results from the therapy that must be applied. Debriding the area, which is the removal of destroyed tissue, charred skin, and any foreign material in the burn, is a painful and time-consuming process.

Widespread full-thickness burns offer the double hazard of entry for infectious agents and an open area for body fluids to escape. Covering the burned area with grafts will help to seal it, will protect the interior of the body from infection, and will prevent the formation of scars. Scar tissue is a nonfunctional tissue that has little elasticity, which means that it can interfere with proper functioning of an extremity. For moderate burns the needed skin graft can be obtained from other areas of the patient's body. A thin patch of skin is removed and is put through a machine that punctures the graft so that it can be expanded, somewhat like the lattice topping of a pie. The area covered by the perforated skin is much greater than is the area that could be covered by the intact skin patch.

Man-made materials also can be used as skin grafts. Individuals who have a full-thickness burn that covers most of their body cannot spare the skin for a graft. Man-made materials can be applied to the burned area to seal it off and allow natural skin to grow back. Whatever the method, treatment of a full-thickness burn is a long and involved procedure that must be closely followed to achieve the desired cure.

Scalds

Scalding, that is burning by steam or hot liquid, differs from contact burns or sunburns. Small children are especially prone to scalds because in their curiosity they may pull a pan from the stove and spill hot water or grease on themselves.

The scalded skin will be painful and in severe cases the skin will be of a lighter color than normal. Skin reaction eventually will parallel that of sunburn or contact burn. A minor scald will result in skin color change and little else. A more severe one will result in the formation of blisters and even tissue destruction. Inhaling steam can burn the lining of the nose, larynx, and trachea, and if hot enough, the bronchi and lungs. Formation of scar tissue following a burn inside the respiratory tract is a serious and possibly lethal situation.

Preventing burns

Obviously, burn prevention is the best measure. Avoiding first- and second-degree burns can be accomplished by spending shorter time spans in the Sun, using an effective sunscreen, and taking care in the kitchen or other areas in which one is at risk for burn.

Light-skinned individuals are more prone to painful sunburn than are people with darker skins. The lack of melanin in the lighter skin offers less protection from the burning ultraviolet rays. Some individuals do not burn readily, but tan quickly when exposed to the Sun. This is the reaction of the melanin-producing cells in the lower level of the skin, which release the dark melanin granules to spread into the epidermis and shield the skin from damaging sun rays. Redhaired people do not have a sufficient number of melanin-producing cells to provide a protective layer. Light-skinned people will burn instead of tan and the burn will be painful and may blister.

Skin that is repeatedly exposed to sunlight is at higher risk for the development of skin cancer. Though it is usually not fatal, skin cancer requires medical attention to prevent its spreading. Those who have close relatives who have had skin cancer are at increased risk for developing it. These individuals should avoid "sunbathing" or they should wear an effective sunscreen when out of doors.

Chemical burns

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.

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. Also, the eyes are 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 if one is exposed to it for some hours. 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.

Obviously, chemicals present a ready source for burns, internal and external. 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 one is 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.

Further Reading

Englebardt S.L. "A Rage against Dying." Reader's Digest. 144 (May 1994): 161-162+.

Larry Blaser

Bush babies see Lorises

KEY TERMS

Angstrom--A unit of length equal to 100-millionth of a centimeter, usually applied to electromagnetic wavelengths.

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

Epidermis--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.

Graft--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.

Hydration--Restoring fluids to the body. Deep and extensive burns allow the escape of fluids needed for proper body functions. Restoring those fluids is called hydration.

Record Number: A30420829

SOURCE:
Burn. Gale Encyclopedia of Science.  June 2001 pNA.

Full Text: COPYRIGHT 2001 Gale Group