A burn is partial or total destruction that may involve:

  • skin;
  • soft tissue parts;
  • even bone.

The severity of the burn depends on several parameters:

  • its location;
  • its topography (a circular burn will always be severe)
  • its depth (the degree of burn)
  • the extent of the damaged area (as a percentage of the total body surface)
  • the causative agent in question.

A burn can be caused by:

  • By contact with a hot source (solid, liquid, or gas);
  • By contact with a caustic substance;
  • By friction;
  • By the effect of combustion (action of a flame);
  • By the effect of radiation (sunburn: ultraviolet B radiation, infrared radiation, X-rays);
  • By the effect of an electric current (electrification);
  • By cold (frostbite).

Burns are injuries to the skin or other tissues caused by contact with :

  • thermal,
  • radiological,
  • chemical
  • electrical.

Burns are classified according to their depth (superficial, or deep) and the percentage of the total body surface area involved. Complications and associated problems include:

  • hypovolemic shock,
  • inhalation injuries,
  • infections,
  • scarring,
  • contractures (a permanent shortening of a muscle or joint).

Victims with extensive burns (>10% of total body surface area) are at high risk of developing hypothermia as a result of their burn injury. The rescuer should ensure that the victim is covered.

Victims with extensive burns (> 20% of total body surface area) require fluid resuscitation while being treated at the receiving hospital. 


Definition and Meaning

Burns are skin injuries caused by heat, chemicals, electricity, cold, radiation or friction. Burns can range in severity from mild to severe, depending on the depth of the skin injury and the size of the affected area. Symptoms of burns can include pain, redness, blistering, ulcers, peeling skin and inflammation. Severe burns can lead to complications such as infection, scarring, loss of mobility and organ failure. Treatment of burns depends on their severity and may include first aid measures such as cooling the affected area, applying a sterile dressing, taking pain medication and administering intravenous fluids. Severe burns often require hospitalization and specialized treatment to prevent complications. Prevention of burns can be achieved by taking appropriate safety measures, such as using protective gloves, avoiding hazardous areas, and safely handling chemicals and electrical equipment.


Thermal burns can result from any external heat source (flame, hot liquid, hot solid object, or occasionally steam). Fires can also result in the inhalation of toxic fumes (see also carbon monoxide poisoning).

Radiation burns most often result from prolonged exposure to the sun's ultraviolet rays (sunburn), but can result from prolonged or intense exposure to other sources of ultraviolet radiation (e.g., tanning beds) or from exposure to sources of x-rays or other non-solar radiation (see Radiation Exposure and Contamination).

Chemical burns can result from strong acids, strong alkalis (e.g., lye, cement), phenols, cresols, mustard gas, phosphorus, and some petroleum products (e.g., gasoline, paint thinner). Skin and deep tissue necrosis caused by these agents may progress over several hours.

Electrical burns result from heat generation and electroporation of cell membranes associated with massive electron currents. High-voltage electrical burns (>1000 volts) often cause deep and extensive damage to electrically conductive tissues, such as muscles, nerves, and blood vessels, despite minimal apparent skin damage.

Events associated with a burn (e.g., jumping from a burning building, being struck by debris, a car accident) can cause further injury. Abuse should be considered in young children and elderly patients with burns (see Child Abuse Overview and see Elder Abuse).


Rule of Nines

The rule of nine is a tool used to estimate the percentage of a burn on the victim's entire skin. It divides your body into sections by multiples of 9% each.

The sections of the rule of nine are as follows:

  • Head: 9%. 
  • Genitals: 1%.
  • Arm: 9%.
  • Legs: 18 
  • Torso: 36%.

Sections of the body can be divided into two. For example, the front of an arm or your head represents 4.5% of your total body surface. The front and back of your torso are 18% each. 

These percentages are accurate for people over the age of 14.

The rule of nines gives an idea of how much of your total body surface area a burn occupies. It helps guide treatment based on the size and intensity of the burn.

First aiders are some of the medical workers who use the Rule of Nines the most. They quickly assess the surface area of the burn to decide on treatments on the way to the hospital.

A medical provider can use the Rule of Nines calculations in several ways. This includes how much fluid to replace and how much care a person needs.

When a person suffers a second-degree burn or worse, the protective layer of the skin is destroyed. As a result, a significant amount of body water is lost. Fluid intake is therefore vital to help a person maintain their total hydration level. According to the National Institutes of Health, burns that are greater than 20-25% of the total body surface area require a significant amount of intravenous (IV) fluids. Physicians will also use the estimated body surface area burned to determine how much fluid to administer.

The rule of nines can also tell the medical team receiving the patient how severe the injury is. Health care providers also know that burns that exceed 30 percent of a person's body surface area can be potentially fatal, according to the National Institutes of Health.


Alternative method

Estimate the percentage reached using the size of the victim's palm as well as fingers with the and not your own.

The Palmer method of estimating total body surface area is an easy way to get a rough estimate of burn size that can be used to calculate a patient's fluid resuscitation needs.

The patient's palmar surface area, including the fingers, represents 1% of the total body surface area.


Why know the total burn percentage?

If a person has burns on 10% or more of their body surface, a burn center should treat their injuries. Other circumstances in which a burn center must treat the injuries are:

  • when the person is a child
  • when the burns affect key areas of the body, such as the hands, feet, genitals, face or major joints
  • chemical burns
  • electrical burns
  • third degree burns

Another example of how a provider can use the rule of nine is to determine the amount of IV access needed. If a person has been burned over 15% or more of their total body surface, they will need at least one peripheral line to provide IV fluids. If a person's body is burned 40% or more, they will need at least two IVs.


The degree of the burns

First degree burns

These are the least serious and most common burns. Only the epidermis is affected. They result in the appearance of redness and increased sensitivity of the affected area. A good example is simple sunburn. These burns do not require special care for their repair, as the skin retains its ability to regenerate. However, the pain usually requires relief. Simple cold water compresses on the burns can be used to alleviate the pain.

Second degree burn

A second-degree burn is defined by the appearance of a phlyctene (water bells). Second-degree burns are divided into two entities:

  • superficial second degree;
  • the deep second degree.

What separates them is the level of damage to the dermis, which will affect the skin's ability to regenerate. The diagnosis of the depth is difficult, even for a professional. Often, the burn will be qualified as "second degree intermediate" and it is the evolution (over a period of 7 to 10 days) that will allow a more precise diagnosis. Areas of varying burn depth can coexist on the same burn.

In a superficial second-degree burn, the skin will regenerate by itself in the absence of superinfection. The deep second degree is distinguished by an impossibility of regeneration. There is a vascular damage and a destruction of the epidermal stem cells. The second deep degree requires a skin graft.

In case of loss of sensitivity (painless burned area), the burn is probably deep. However, this sign lacks specificity and does not really guide medical management.

Third degree burns

These are the most serious burns. They destroy the entire skin (dermis and epidermis). The damaged skin takes on a white, brown or black color. These areas become insensitive, dry and prone to infection. In this case, there is no possibility for the skin to regenerate itself because all the skin cells are missing. Skin grafting is then essential for the survival of the victim in case of extensive injury.

Fourth degree burns

The burn is so deep that it reaches the subcutaneous structures such as bones and muscles. This situation is critical and can only be improved by surgical intervention. The skin is charred and has a cardboard-like appearance.



Treatment begins in the prehospital setting. The first priorities are the same as for any injured patient: ABC (airway, breathing, and circulation). The airway is cleared, ventilation is supported, and any associated smoke inhalation is treated with 100% oxygen. Ongoing burns are extinguished, and smoking and hot materials are removed. All clothing is removed. Chemicals, except powders, are rinsed with water; powders should be brushed off before wetting. Burns caused by acids, alkalis, or organic compounds (e.g., phenols, cresols, petrochemicals) are rinsed with copious amounts of water for at least 20 minutes after nothing of the original solution remains.

After adequate analgesia, the wound is cleaned with soap and water and all loose debris is removed. The water should be room temperature or warmer to avoid causing hypothermia. Ruptured blisters, with the exception of small blisters on the palms, fingers, and soles of the feet, are debrided. Unruptured blisters can sometimes be left intact but should be treated with a topical antimicrobial. In patients who need to be transferred to a burn center, clean, dry dressings can be applied (burn creams may interfere with wound assessment at the receiving facility), and patients are kept warm and relatively comfortable with IV opioids.

Once the wound is cleaned and assessed by the final provider, burns can be treated topically. For shallow partial burns, topical treatment alone is usually sufficient. All deep partial-thickness burns and full-thickness burns must ultimately be treated with excision and grafting, but until then, topical treatments are appropriate.