Which type of burn extends into the underlying fat and may require surgical intervention?

A burn that extends into the underlying fat is classified as a third-degree burn. This type of burn is characterized by damage to all layers of the skin, including the epidermis and dermis, and can affect deeper tissues like fat. Third-degree burns typically appear leathery, dry, and may vary in color from white to charred. Because they destroy the skin's ability to regenerate and can lead to significant complications such as infection or fluid loss, surgical intervention, including skin grafting, is often necessary to facilitate healing and restore function.

In contrast, first-degree burns affect only the outer layer of skin (epidermis) and typically heal without scarring. Second-degree burns can involve both the epidermis and part of the dermis, resulting in blisters but generally heal without surgical intervention. Fourth-degree burns go deeper, affecting muscle and bone, requiring extensive medical treatment and often resulting in significant functional impairment. While they are serious, the question specifically asks about burns extending to the fat layer, making third-degree burns the correct answer.