Cold produces injury by increasing the rate of body-heat loss. This rate is determined not only by the ambient temperature, but also by other factors such as moisture and wind. Moisture increases the rate of heat loss by conduction and evaporation, wind by convection. A variety of environmental and host factors combines in the total causation of cold injury and influences the incidence, prevalence, type, and severity of the injury, though these influences vary from situation to situation. The most important environmental factors in cold injury are weather, clothing, and type of combat action.
Weather is a predominant influence in the causation of cold injury.
Temperature, humidity, precipitation, and wind modify the rate of loss of body heat. Low temperatures and low relative humidity favor the development of trenchfoot. The type of combat action is apparently the most important environmental factor. Units in reserve or in rest areas have few cases. Units on holding missions or on static defense, in which exposure is greater, show a moderate increase in incidence.