The skin is composed of multiple layers of cells. A burn injury to the skin affects the surface first and, as the burn gets more severe, it penetrates deeper into the layers of the skin.
The most superficial burn is called a first-degree burn. This appears red but does not have any peeling skin or blisters. A first-degree burn is painful because the ends of the nerves are inflamed but recovers fully and without a scar.
The next level burn is called a second-degree burn and it can be superficial or deep. The superficial type is characterized by blistering or peeling skin. This burn extends below the outer layer of the skin into the dermis. Superficial second-degree burns usually heal well but are subject to getting infected in which case they can convert to a deeper level burn. Deep second-degree burns extend into the depths of the dermis and are significant and dangerous injuries. Most of the support structure for the skin’s function is disrupted. The skin is a barrier to infection, a way of keeping foreign material including liquids and solids out of the body and of keeping bodily fluids and structures inside the body. The nerves are damaged in a deep second-degree burn and it is less painful than a more superficial burn. However, it heals with a noticeable and sometimes deforming scar. All but small deep second-degree burns require surgery to remove the dead portions of the skin and to skin graft or otherwise provide coverage to the exposed surface. These usually appear pale and sometimes are blackened in flame burns.
Third degree burns are the most damaging as all the skin layers are destroyed. Generally, the dead skin forms an eschar which is a scab of dead skin. Initially it can look whitish or reddish, but as the dead skin cells dry up, it turns into a leathery adherent surface layer. It does not protect the body the way living skin does, resulting is severe metabolic changes and systemic illness in the patient. Almost all third degree burns except for very small ones require extensive surgery and frequently multiple surgeries. The deeper burn injuries can result in death or severe permanent deformities and loss of function.