A fourth-degree burn is one that burns through all the layers of the skin, all the way down to the muscle, tendons and ligaments. Depending on how much skin is affected by the burn, a fourth-degree burn can be fatal.
There are six degrees of burns. First-degree burns are similar to a sunburn. Second-degree burns are red, blistering burns that affect deeper layers of skin. Third-degree burns go all the way through the skin and often destroy nerve endings. Fourth-degree burns give the skin a charred appearance. Fifth- and sixth-degree burns are often only diagnosed during an autopsy. These types of burns destroy everything from the skin to the bone.