Which description corresponds to 3rd-degree frostbite?

• A. Formation of clear bullae, numbness followed by aching and throbbing
• B. Extends deeper into muscle with mottled skin
• C. Freezing of skin and subdermal plexus with hemorrhagic bullae and skin necrosis
• D. Partial thickness skin freezing with erythema and edema

Answer: (C)

The key idea is that frostbite depth tracks the amount of tissue that is frozen and damaged. Third-degree frostbite means the freezing extends beyond the surface into deeper vessels in the skin—specifically the subdermal plexus—causing significant tissue injury. The description of freezing that involves the skin and subdermal plexus with hemorrhagic bullae and skin necrosis matches this level of depth: the subdermal vessels are injured, blisters become hemorrhagic, and necrosis can develop.

To put it in context, milder frostbite forms are more superficial. First-degree frostbite (frostnip) affects only the epidermis, with redness, numbness, and no blisters. Second-degree frostbite involves deeper skin and may form clear or fluid-filled blisters but typically lacks necrosis. Fourth-degree frostbite goes even deeper, involving muscle, tendon, or bone.