It should be noted that it is difficult to differentiate first-degree frostbite from abrasion produced by the insulated vapor barrier boot. Medical personnel must be cognizant of the difference as both injuries occur in the same clinical setting. Edema may form, but it disappears within days. Vesicles appear within 12-24 hours. They generally appear on the dorsum of the extremities, and when these vesicles dry they form an eschar.
Blisters are a good clinical sign as long as they are filled with clear fluid.
If the fluid is hemorrhagic, they are not a good sign. As these vesicles dry, they sluff cleanly with pink granulation tissue beneath or they form black eschars. Throbbing and aching pain occurs 3-10 days after this injury. Hyperhydrosis is apparent at the second or third weeks. Early rupture of the blisters with subsequent infection often occurs in second-degree cold injury.