Final answer:
Critical burns include third and fourth-degree burns that can appear white, red, or black, and they may not be painful due to nerve damage. Treatment requires medical intervention, including potential skin grafting, and careful management to prevent infection.
Step-by-step explanation:
The symptoms of critical burns include the appearance of the skin being white, red, or black, the destruction of both epidermis and dermis layers, and damage to nerve endings. Such burns might not be painful due to nerve damage. The appropriate treatment for serious burns such as third and fourth-degree burns involves medical attention, possibly including excision (debridement), amputation, and grafting of skin from another part of the body or from tissue culture. It's also crucial to handle these burns with great care to prevent infection and support the healing process with intravenous fluids and nutrients.