Burn injuries occur when the skin and underlying tissues are damaged due to exposure to heat, electricity, chemicals, radiation, or friction. They can vary in severity, from minor superficial burns to severe deep burns that can be life-threatening.

The damage results in the death of skin cells, which can lead to a massive loss of fluid. Dehydration, electrolyte imbalance, and renal and circulatory failure follow, which can be fatal. Burn patients are treated with intravenous fluids to offset dehydration, as well as intravenous nutrients that enable the body to repair tissues and replace lost proteins. Another serious threat to the lives of burn patients is infection. Burned skin is extremely susceptible to bacteria and other pathogens, due to the loss of protection by intact layers of skin.

In addition to the depth of the burn, burns are also classified by the total body surface area (TBSA) affected. The "Rule of Nines" is commonly used to estimate the TBSA involved in adults, where each major body part is assigned a percentage (e.g., the head is 9%, each arm is 9%, the front chest and abdomen are 18%, etc.). For children, a modified rule is used to account for the differences in body proportions.

Burns are also classified by the degree of their severity:

A first-degree burn is a superficial burn that affects only the epidermis. Although the skin may be painful and swollen, these burns typically heal on their own within a few days. Mild sunburn fits into the category of a first-degree burn.

A second-degree burn goes deeper and affects both the epidermis and a portion of the dermis. These burns result in swelling and painful blistering of the skin. It is important to keep the burn site clean and sterile to prevent infection. If this is done, the burn will heal within several weeks.

A third-degree burn fully extends into the epidermis and dermis, destroying the tissue and affecting the nerve endings and sensory function. These are serious burns that may appear white, red, or black; they require medical attention and will heal slowly without it. Oddly, third-degree burns are usually not as painful because the nerve endings themselves are damaged. Full-thickness burns cannot be repaired by the body, because the local tissues used for repair are damaged. They require excision (debridement), or amputation in severe cases, followed by grafting of the skin from an unaffected part of the body, or from skin grown in tissue culture for grafting purposes.

Treatment for burn injuries depends on the severity and extent of the burns. It may involve cleaning and debriding the wound, applying topical medications or dressings, administering pain medications, and providing supportive care such as intravenous fluids and nutritional support. Severe burns often require specialized care in burn centers or hospitals with expertise in burn management.

This text is adapted from Openstax, Anatomy and Physiology 2e, Section 5.4: Diseases, Disorders, and Injuries of the Integumentary System.