Burns are injuries that occur when skin tissue is damaged by thermal energy. They can range from mild discomfort to severe tissue destruction. Even moderately warm temperatures can cause significant harm if exposure lasts long enough.
Temperature Thresholds for Skin Damage
Skin registers pain at temperatures just above normal body temperature, with discomfort beginning around 109.4°F (43°C). True burn injury to the epidermis can occur at 111.2°F (44°C). While brief contact with 120°F (49°C) might cause discomfort, prolonged exposure leads to serious damage. For example, a second-degree burn can develop after 30 seconds at 120°F, and a third-degree burn after five minutes.
As temperatures increase, the time to sustain a burn significantly decreases. At 130°F (54°C), a second-degree burn can occur in 10 seconds. At 140°F (60°C), a second-degree burn can happen in 3 seconds, and a third-degree burn in 5 seconds; pain receptors may even become numb. At 160°F (71°C) or higher, burns can occur almost instantaneously, with tissue destroyed on contact at 162°F (72°C). These timelines are general guidelines, influenced by individual sensitivity and heat source properties.
Factors Affecting Burn Severity
Beyond temperature and duration, several other elements influence burn severity. Prolonged contact with a heat source, even at lower temperatures, can cause profound damage. The type of heat source also plays a role, as conductive heat from solids or liquids, like hot water, transfers energy differently than convective heat from steam or hot air. Scald burns from hot liquids are common, especially among children.
Skin thickness and total body surface area affected also modify burn severity. Thinner skin, found in children and older adults, is more susceptible to deeper burns. Burns covering a larger percentage of the body are generally more serious. Certain body parts are also more vulnerable, such as the face, hands, feet, and groin. In contrast, palms and soles have naturally thicker skin, offering increased resistance to injury.
Underlying health conditions can complicate the body’s response to thermal injury. Individuals with chronic illnesses or those at the extremes of age, like very young children and the elderly, may experience more severe outcomes and a challenging recovery.
How Burns Progress
Burns are characterized by the depth of skin tissue damage. First-degree burns are superficial, affecting only the outermost layer of skin, the epidermis. They present with redness, pain, and tenderness, but without blistering. They typically result from brief contact with moderate heat and heal within a week without scarring.
Second-degree burns extend deeper, damaging the epidermis and part of the underlying dermis. They are characterized by blistering, redness, swelling, and pain. Depending on dermal involvement, they can be superficial or deep partial-thickness burns. While superficial second-degree burns heal within a few weeks, deeper ones may take longer, potentially resulting in scarring or requiring skin grafting.
Third-degree burns are the most severe form of thermal injury, destroying the epidermis and entire dermis, sometimes extending into deeper tissues like fat, muscle, or bone. The affected skin may appear white, leathery, or charred. Due to nerve ending destruction, there may be little to no pain at the burn site. These burns result from intense heat or prolonged exposure and require immediate medical attention, often necessitating skin grafting.