What indicates a fourth-degree burn?

A fourth-degree burn is characterized by damage that extends beyond the skin into deeper tissues, including muscles, tendons, and even bone. This type of burn is the most severe and can result in extensive tissue loss and potential complications, including infections and significant scarring.

In the context of the other options, they describe burns of lesser severity. For instance, burns that affect only the epidermis indicate a first-degree burn, which presents with minimal symptoms like redness and slight swelling. Severe blistering is characteristic of a second-degree burn, which penetrates deeper into the dermis. Lastly, the option that describes burns resulting in redness and mild swelling pertains to first-degree burns. Thus, only the identification of underlying tissue damage, including bone, accurately describes the severity of a fourth-degree burn.