A burn injury usually results from an energy transfer to the body. There are many types of burns caused by thermal, radiation, chemical, or electrical contact.
Thermal burns: Thermal and chemical burns usually occur because heat or chemicals contact part of the body's surface, most often the skin. Thus, the skin usually sustains most of the damage. However, severe surface burns may penetrate to deeper body structures, such as fat, muscle, or bone. Hot metals, scalding liquids, steam, and flames, when coming in contact with the skin, can cause thermal burns.
Chemical burns: Chemical burns are caused by caustic substances that contact the skin. Caustic substances are sometimes found in household products, including those containing lye (in drain cleaners and paint removers), phenols (in deodorizers, sanitizers, and disinfectants), sodium hypochlorite (in disinfectants and bleaches), and sulfuric acid (in toilet bowl cleaners). Many chemicals used in industry and during armed conflicts can cause burns. Wet cement left on the skin can cause severe burns as well.
Radiation burns: Radiation burns are burns due to prolonged exposure to ultraviolet rays (UV) of the sun or to other sources of radiation, such as x-ray or gamma radiation therapy for cancer. Radiation burns can also be caused by tanning booths and sunlamps. A sunburn is literally a burn on the skin from ultraviolet radiation. The consequence of this burn is swelling and redness of the skin. Injury can start within 30 minutes of exposure. UVA and UVB refer to different wavelengths in the light spectrum. UVB is more damaging to the skin and the main UV cause of skin cancer. Both UVA and UVB are responsible for photo aging (premature aging of the skin and wrinkles) and sunburn. UVA rays are predominately responsible for the aging process. Tanning beds produce both UVA and UVB rays.
Prior recent sun exposure and prior skin injury are risks for sunburn, even in limited exposure to the sun. Travel to the southern United States, regions close to the equator, and places at high altitudes all offer the unwary visitor an opportunity to be injured by sunburn. Certain light-skinned and fair-haired people are at greater risk of sunburn injury.
A benefit of UV radiation is the production of beneficial vitamin D in the skin.
Friction burns: Friction burns are caused by contact with any hard surface such as roads ("road rash"), carpets, or gym floor surfaces. They are usually both a scrape (abrasion) and a heat burn. Friction burns to the skin are seen in athletes who fall on floors, courts, or tracks. Motorcycle or bicycle riders who have road accidents while not wearing protective clothing might get friction burns.
Electrical burns: An electrical burn may appear minor or not show on the skin at all, but the damage can extend deep into the tissues beneath the skin. If a strong electrical current passes through the body, internal damage, such as a heart rhythm disturbance or cardiac arrest, can occur. Sometimes the jolt associated with the electrical burn can cause the individual to be thrown or to fall, resulting in fractures or other associated injuries.
If the burn is severe enough for the individual to be taken to the hospital, the doctor will take a history and perform a physical examination to determine the extent and severity of the burn. In determining the extent of the burn, the doctor may use a tool called the Rule of Nines. This tool is a formula that divides the surface area of the body into sections, each roughly 9%. Determining the amount of surface area burned helps the doctor with treatment of the burn. The doctor will determine whether the burn or burns are superficial, partial thickness, or full thickness and then begin appropriate treatment.
Special charts are used to show what percentage of the body surface various body parts comprise. For example, in an adult, the arm constitutes about 9% of the body. Separate charts are used for children, because their body proportions are different. All first-degree burns as well as second-degree burns that involve less than about 15% of the body surface usually are classified as minor, although they may seem severe to the person. A third-degree burn may be classified as minor if it involves less than 5% of the body surface, unless it involves the face, hands, feet, or genitals. Burns involving these areas or involving deeper layers of skin over larger areas of the body are classified as moderate or, more often, as severe.
In addition to the intensity, the total area of the burn is significant. This is usually measured in terms of percent of total body burnt. The skin acts as a barrier from the environment, and without it, patients are subject to infection and fluid loss. Burns that cover more than 15% of the total body surface can lead to shock and require hospitalization for intravenous fluid resuscitation and skin care.
Because the age of a burn victim and the percentage of the body's surface area that has been burned are the two most important factors affecting the prognosis of a burn injury, the American Burn Association recommends that burn patients who meet the following criteria should be treated at a specialized burn center: younger than 10 years or older than 50 years with partial- or full-thickness burns over 10% or more of the total body surface area (TBSA); age 10 years or older or age 50 years or younger with partial- or full-thickness burns over 20% or more of the TBSA; any age with full-thickness burns covering 5% or more of the TBSA; burns of the face, hands, feet, or perineum (groin, or genital area), or burns that extend all the way around a portion of the body; burns accompanied by an inhalation injury affecting the airway and/or the lungs; burn patients with existing chronic conditions such as diabetes, high blood pressure, heart disease, kidney disease, or multiple sclerosis; chemical burns; electrical injury; scald burns; grease burns; tar burns; and radiation burns.
signs and symptoms
First-degree burns: First-degree burns (or superficial burns) involve only the epidermis, or the outermost layer of the skin. First-degree burns are red, moist, swollen, and painful. The burned area whitens (blanches) when lightly touched but does not develop blisters. Sunburns are generally considered first degree burns.
Second-degree burns: Second-degree burns (or partial thickness burns) involve the epidermis and some portion of the dermis, the second layer of the skin. This type of burn may be broken down into superficial or deep, depending on how much of the dermis is involved. Superficial signs and symptoms include pain and redness at the burn site. This area may turn white to touch and appear discolored, blistered, and moist. Hairs may still be present. Deep signs and symptoms include: may or may not be painful, due to the fact that burns may be so deep that nerve endings have been destroyed; may be moist or dry, as sweat glands may have been destroyed; may or may not turn white when area is touched; and hairs are usually gone.
Third-degree burns: Third-degree burns (or full thickness burns) are the most severe. Third-degree burns involve all of the epidermis and dermis - the first two layers of the skin. Nerve endings, tiny blood vessels, hair follicles, and tiny sweat glands are all destroyed. If very severe, the burn may involve bone and muscle. Third degree burn areas are painless (due to damaged nerve endings). There is no sensation to touch, and they appear pearly white or charred, dry, and possibly leathery. No blisters develop. The appearance and symptoms of deep burns can worsen during the first hours or even days after the burn.
Most minor burns are superficial and do not cause complications. However, deep second-degree and third-degree burns swell and take more time to heal. In addition, deeper burns can cause scar tissue to form. This scar tissue shrinks (contracts) as it heals. If the scarring occurs at a joint, the resulting contracture may restrict movement. Thick, crusty surfaces (eschars) are produced by deep third-degree burns. Eschars can become too tight, cutting off blood supply to healthy tissues or impairing breathing if occurring near the throat. Burns can also cause emotional problems, such as depression, nightmares, or flashbacks from the traumatizing event. The loss of a friend or family member and possessions in a fire may add grief to the emotional strain of a burn.
A severe burn (third-degree) can be a seriously devastating injury, not only physically but emotionally. A severe burn can not only affect the burn victim, but the entire family. Individuals with severe burns may be left with a loss of certain physical abilities, disfigurement, loss of a limb, loss of mobility, scarring, and infection. In addition, severe burns are capable of penetrating deep skin layers, causing muscle or tissue damage that may affect every system of the body.
Severe burns can cause serious complications due to extensive fluid loss and tissue damage. Complications from severe burns may take hours to develop. The longer the complication is present, the more severe the problems it tends to cause. Young children and older adults tend to be more seriously affected by complications than other age groups.
Dehydration eventually develops in people with widespread burns, because fluid seeps from the blood to the burned tissues. Shock develops if dehydration is severe. Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. Destruction of muscle tissue (rhabdomyolysis) occurs in deep third-degree burns. The muscle tissue releases myoglobin, one of the muscle's proteins, into the blood due to muscle tissue breakdown. If present in high concentrations, myoglobin harms the kidneys. Rhabdomyolysis can be diagnosed from tests of the blood and urine.