||Tissue damage from extreme cold is similar in appearance to heat injury. Exposure to cold temperatures causes prolonged vasoconstriction of the capillary wall, with resulting anoxic capillary wall damage. After the ear has been warmed, the capillaries dilate, producing a bright red color resembling a first-degree burn. There is often an accompanying sensation of burning or itching in the affected areas during rewarming.
Cell wall damage may also occur from ice crystal formation, which expands and disrupts cell membranes. Rubbing of the frostbitten ear is ill-advised, since this will only increase the mechanical damage to the tissues.
The erythema over the outer aspect of the ear on the left resembles a first-degree burn.