Cold protecting emollients and frostbite

Abstract Frostbite of the face and ears is a common problem in cold winters. Application of an emollient on the face is a traditional way to prevent frostbite in Finland. The preliminary results of an epidemiological study on frostbite in Finnish conscripts unexpectedly showed that the use of cold protecting emollients increased the risk of facial frostbite. This finding motivated studies on the effects and use of cold protecting emollients. 830 male Finnish conscripts answered a questionnaire concerning the use of cold protecting emollients, subjective experience of using them in cold and cumulative incidence of frostbite in the ears and face. Risk factors of frostbite were investigated in a prospective epidemiological study including 913 Finnish conscripts needing medical attention for frostbite of the ears or face and their 2478 matched, uninjured controls. Thermal properties of four different emollients were studied in vitro with a skin model and in vivo in experimental cold exposures of test persons. Test emollient was applied on one half of the face, as the other half acted as control. The skin temperatures of the face-halves were compared symmetrically by thermistors and infrared thermography. Subjective sensation of thermal half-difference was also registered. 21% of the conscripts had used emollients in the cold, a majority with an experience of protection. 47% of the conscripts had had frostbite in the head (42% in the ears and 23% on the face). There was a statistically significant correlation between the use of emollients and the incidence of facial frostbite in both epidemiological studies. Applying protective emollients formed an independent risk factor for frostbite of the cheeks, nose and ear lobes (odds ratios 3.3-5.6). The thermal insulation of test emollients on the skin model was minimal. On living skin, the applied half was somewhat cooler in a majority of comparisons. However, white petrolatum gave often a subjective perception of a warming effect. False sensation of safety may form the principal cause for the increased risk of frostbite associated with the use of emollients. When the warning symptoms of cold are weak, necessary protective measures are not carried out