Burns are injuries to tissue that result from heat, electricity, radiation, or chemicals.
Burns are usually caused by heat (thermal burns), such as fire, steam, tar, or hot liquids. Burns caused by chemicals are similar to thermal burns, whereas burns caused by radiation (see Radiation Injury), sunlight (see Overview of Sunlight and Skin Damage), and electricity (see Electrical Injuries) differ significantly. Events associated with a burn, such as jumping from a burning building, being struck by debris, or being in a motor vehicle crash, may cause other injuries.
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.
When tissues are burned, fluid leaks into them from the blood vessels, causing swelling. In addition, damaged skin and other body surfaces are easily infected because they can no longer act as a barrier against invading microorganisms.
More than 2 million people in the United States require treatment for burns each year, and between 3,000 and 4,000 die of severe burns. Older people and young children are particularly vulnerable. When children and elderly people are burned, doctors also consider the possibility that the person was abused.
Doctors classify burns according to strict, widely accepted definitions. The definitions classify the burn's depth and the extent of tissue damage.
The depth of injury from a burn is described as first, second, or third degree:
Burns are classified as minor, moderate, or severe. These classifications may not correspond to a person's understanding of those terms. For example, doctors may classify a burn as minor even though it can cause the person significant pain and interfere with normal activities. The severity determines how they are predicted to heal and whether complications are likely. Doctors determine the severity of the burn by its depth and by the percentage of the body surface that has second- or third-degree burns. 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.
Symptoms and Diagnosis
Symptoms of a burn wound vary with the burn's depth:
The appearance and symptoms of deep burns can worsen during the first hours or even days after the burn.
Doctors frequently examine hospitalized people for complications and assess burn wound depth and extent. In people with large burns, blood pressure, heart rate, and urine volume are measured often to help assess the extent of dehydration or shock and the need for intravenous fluids. Doctors do blood tests to monitor the body's electrolytes and blood count. Electrocardiography (ECG) and chest x-ray are also required. Tests of blood and urine are done to detect proteins caused by the destruction of muscle tissue (rhabdomyolysis) that sometimes occurs with deep third-degree burns.
Minor burns are usually 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 in a limb or digit, the resulting contracture may restrict movement of nearby joints.
Severe burns and some moderate burns can cause serious complications due to extensive fluid loss and tissue damage. These complications may take hours or days to develop. The deeper and more extensive the burn, the more severe are the problems it tends to cause. Young children and older adults tend to be more seriously affected by complications than other age groups. The following are some complications of some moderate and severe burns:
Before burns are treated, the burning agent must be stopped from inflicting further damage. For example, fires are extinguished. Clothing—especially any that is smoldering (such as melted synthetic shirts), covered with a hot substance (for example, tar), or soaked with chemicals—is immediately removed.
Hospitalization is sometimes necessary for optimal care of burns. For example, elevating a severely burned arm or leg above the level of the heart to prevent swelling is more easily accommodated in a hospital. In addition, burns that prevent people from carrying out essential daily functions, such as walking or eating, or that cause severe pain, often make hospitalization necessary. Severe burns, deep second- and third-degree burns, burns occurring in the very young or the very old, and burns involving the hands, feet, face, or genitals are usually best treated at burn centers. Burn centers are hospitals that are specially equipped and staffed to care for burn victims.
Superficial minor burns:
Superficial minor burns are immersed immediately in cool water if possible. The burn is carefully cleaned to prevent infection. If dirt is deeply embedded, doctors can give analgesics or numb the area by injecting a local anesthetic and then scrub the burn with a brush.
Often, the only treatment required is application of an antibiotic cream, such as silver sulfadiazine. The cream prevents infection and forms a seal to prevent further bacteria from entering the wound. A sterile bandage is then applied to protect the burned area from dirt and further injury. A tetanus vaccination is given if needed (see Tetanus).
Care at home includes keeping the burn clean to prevent infection. In addition, many people are given analgesics, often opioids, for at least a few days. The burn can be covered with a nonstick bandage or with sterile gauze. The gauze can be removed without sticking by first being soaked in water.
Deep minor burns:
As with more superficial burns, deep minor burns are treated with antibiotic cream. Sometimes doctors do not use antibiotic cream but instead apply special sterile dressings that can be left in place for several days to a week. Some of these dressings contain silver, which helps kill bacteria. Other dressings are slightly porous—just enough to allow fluid to drain from the burn but not enough to let bacteria through. Any dead skin and broken blisters should be removed by a health care practitioner before the antibiotic cream or dressing is applied. In addition, keeping a deeply burned arm or leg elevated above the heart for the first few days reduces swelling and pain. The burn may require admission to a hospital or frequent re-examination at a hospital or doctor's office, possibly as often as daily for the first few days.
A skin graft may be needed. Some skin grafts replace burned skin that will not heal. Other skin grafts help by temporarily covering and protecting the skin as it heals on its own. In a skin grafting procedure, a piece of healthy skin is taken from an unburned area of the person's body (autograft), a dead person (allograft), or an animal (xenograft). Autografts can be solid pieces of skin or meshed grafts. For a meshed graft, doctors use a tool to make multiple, regularly spaced, small incisions in the piece of skin. The incisions allow the donor skin to be stretched to cover a much larger area (often several times the area of the original piece of skin). Meshed grafts are used in areas where appearance is less of a concern and when burns involve more than 20% of the body surface and donor skin is scarce. Meshed grafts heal with an uneven gridlike appearance, sometimes with excessive scarring. After any dead tissue is removed and the wound is clean, a surgeon sews or staples the skin graft over the burned area. Artificial skin can also be used. Autografts are permanent. Allografts and xenografts, however, are rejected after 10 to 21 days by the person's immune system, and artificial skin is removed. Although allografts and xenografts provide temporary protection to healing skin, an autograft eventually must be placed if the wound is full-thickness and is too large to heal by itself. Burned skin can be replaced anytime within several days of the burn.
Physical and occupational therapy usually are needed to prevent immobility caused by scarring around the joints and to help people function if joint motion is limited. Stretching exercises are started within the first few days after the burn. Splints are applied to ensure that joints that are likely to be immobile rest in positions that are least likely to lead to contractures. The splints are left in place except when the joints are moved. If a skin graft has been used, however, therapy is not started for 3 days after the grafts are attached so that the healing graft is not disturbed. Bulky dressings that put pressure on the burn can prevent large scars from developing.
Severe, life-threatening burns require immediate care. People who have gone into shock as a result of dehydration are given oxygen through a face mask.
Large amounts of intravenous fluids are given, beginning immediately, for people who have dehydration, shock, or burns that cover a large area of the body. Fluids are also given to people who develop destruction of muscle tissue. The fluids dilute the myoglobin in the blood, preventing extensive damage to the kidneys. Sometimes a chemical (sodium bicarbonate) is given intravenously to help dissolve myoglobin and thus also prevent further damage to the kidneys.
A surgical procedure to cut open eschars that cut off blood supply to a limb or that impair breathing may be needed. This procedure is called escharotomy. Escharotomy usually causes some bleeding, but because the burn causing the eschar has destroyed the nerve endings in the skin, there is little pain.
Skin care is extremely important. Keeping the burned area clean is essential, because the damaged skin is easily infected. Cleaning may be accomplished by gently running water over the burns periodically. Wounds are cleaned and bandages changed at various intervals (usually once per day or less frequently), depending on the type of dressing. Skin grafts are needed to cover burns that will not heal.
A proper diet that includes adequate amounts of calories, protein, and nutrients is important for healing. People who cannot consume enough calories may drink nutritional supplements or receive them by way of a tube inserted through the nose into the stomach (a nasogastric tube), or less often nutrition may be given intravenously. Additional vitamins and minerals are usually given.
Physical and occupational therapy are needed.
Depression is treated. Because severe burns take a long time to heal and can cause disfigurement, people can become depressed. Depression often can be relieved with drugs, psychotherapy, or both.
First- and some second-degree burns heal in days to weeks without scarring. Deep second-degree and small third-degree burns take weeks to heal and usually cause scarring. Most require skin grafting. Burns that involve more than 90% of the body surface, or more than 60% in an older person, are often fatal.
Last full review/revision August 2013 by Steven E. Wolf, MD