Immersion (trench) foot is most likely to occur under which conditions?

• A. Dry exposure to cold air
• B. Short exposure to warm indoor environment
• C. Exposure to cold air without moisture
• D. Prolonged exposure (12 hours to 4 days) to cold and wet conditions

Answer: (D)

Immersion (trench) foot arises when the feet are kept wet and exposed to cold for a long period. Moisture dramatically increases heat loss from the skin, and sustained cooling with poor perfusion from vasoconstriction leads to tissue damage even if the air isn’t extremely cold. The critical factor is the duration of exposure combined with moisture, roughly spanning many hours to days, which is when the characteristic numbness, swelling, and potential tissue injury develop.

If feet are dry in cold air, or exposed only briefly to a warm indoor environment, or exposed to cold air without moisture, the conditions aren’t providing that prolonged wet-cold stress needed for trench foot to occur.