“Because of an increased risk of infection, simple non-tense areas of clear blistering in a frostbitten patient are best left intact. Tense or hemorrhagic blisters may be carefully aspirated, but only under sterile conditions. Rapid rewarming of affected areas is best done in a whirlpool bath containing a mild antiseptic at 40°C–41°C. Freezing injuries are extremely painful and analgesics are indicated. Vigorous rubbing of affected tissue is contraindicated, as it may lead to further tissue loss.
Hallam MJ, Cubison T, Dheansa B, Imray C: Managing frostbite. BMJ 2010;341:c5864.” AAFP