Immersion foot is a nonfreezing cold injury (NFCI) of the peripheral neurovasculature caused by prolonged exposure to cold (0–15°C / 32–59°F), wet conditions, typically affecting the feet. [1-2] It is a clinical diagnosis that progresses through four distinct stages and is commonly encountered in homeless, military, and outdoor-exposed populations. [3-4] The critical management pearl: avoid rapid active rewarming — this distinguishes treatment from frostbite. [1][5]
1. History
- Duration and conditions of cold/wet exposure — typically ≥12 hours to several days in wet environments at temperatures above freezing but below 15°C (59°F) [6-7]
- Ask about continuous wearing of wet socks/footwear without removal [6]
- Onset of numbness lasting >30 minutes is the most common initial symptom [2]
- Progression: numbness → clumsiness/gait disturbance → pain on rewarming → burning/tingling [2][5]
- Ability to ambulate, prior episodes, and access to dry clothing/shelter
- Constricting footwear or wraps (e.g., tight boots, puttees) [2]
2. Alarm Features
- Tissue necrosis, hemorrhagic bullae, or gangrene — suggests severe injury or concomitant frostbite/pressure necrosis [8-9]
- Signs of secondary infection: cellulitis, purulent drainage, lymphangitis, fever [2][8]
- Absent peripheral pulses or capillary refill — consider arterial thrombosis [9]
- Concurrent hypothermia — assess core temperature [4]
- Severe cases may progress to sepsis or require amputation [8-9]
3. Medications
- Amitriptyline 50–100 mg PO at bedtime — likely the most effective analgesic for NFCI pain; start as soon as pain develops [1-2]
- Gabapentin — second-line if amitriptyline is inadequate for neuropathic pain [2]
- NSAIDs (ibuprofen) — may provide some relief but usually insufficient as sole therapy [2][5]
- Opioids — generally ineffective as sole treatment; may be needed for severe acute pain [2][5]
- Nifedipine — has NOT been shown effective for NFCI pain relief (unlike its use in chilblains) [2]
- Iloprost (prostacyclin analog) — some evidence for vasodilation benefit in severe cases [8]
- Avoid rapid rewarming agents or active heat application [1][5]
- Update tetanus prophylaxis if skin integrity is compromised [2]
4. Diet
- Malnutrition is a risk factor — adequate caloric intake helps prevent NFCI [2][8]
- Ensure adequate hydration and nutrition during recovery
- In WWI, increased rations sent to the trenches helped nearly eliminate trench foot [2]
- No specific dietary restrictions during recovery
5. Review of Systems
- Neurologic: numbness, paresthesias, burning pain, cold sensitivity, proprioceptive loss [1-2]
- Vascular: color changes (pallor → cyanosis → erythema), edema, diminished pulses [5][7]
- Dermatologic: skin maceration, blistering, ulceration, fungal infection [8][10]
- Constitutional: fever, chills (suggests secondary infection or concurrent hypothermia) [2]
- Musculoskeletal: gait disturbance, difficulty with weight-bearing [2]
- Psychiatric: assess for substance use, psychiatric illness affecting self-care [3][11]
6. Collateral History and Family History
- Collateral: Circumstances of exposure — living situation (homeless, military deployment, outdoor recreation), duration outdoors, access to dry footwear [3][11]
- Substance use history — alcohol and drug use impair thermoregulation and self-care; alcoholic peripheral neuropathy compounds injury risk [10]
- Mental health status — psychiatric illness (e.g., schizophrenia) may impair ability to seek shelter or change socks [3]
- Family history is generally not contributory, though some individuals may have increased susceptibility to cold-induced vasoconstriction [12]
7. Risk Factors
- Homelessness — up to 20% of medical complaints in homeless populations are foot-related; immersion foot is common [10-11]
- Military service — prolonged field operations in cold/wet environments [2][13]
- Prolonged immobility — sitting or standing in wet conditions [2][10]
- Constricting footwear — tight boots, wet socks worn continuously [2][6]
- Malnutrition [2][8]
- Peripheral vascular disease, diabetes, venous hypertension, lymphedema [8][10]
- Alcohol/substance use — impairs thermoregulation and pain perception [4][10]
- Psychiatric illness — impairs self-care behaviors [3]
- Prior NFCI — increases susceptibility to future cold injury [12]
- African descent — some military data suggest increased susceptibility [12]
8. Differential Diagnosis
- Frostbite — freezing injury (tissue temperature <0°C); distinguished by ice crystal formation, hemorrhagic bullae, and history of sub-zero exposure; treated with rapid rewarming (opposite of NFCI) [2][5]
- Chilblains (pernio) — superficial erythrocyanotic papules after brief cold/wet exposure (1–5 hours); pruritic; self-limited [5][7]
- Cellulitis — usually unilateral, well-demarcated erythema with warmth; NFCI is typically bilateral and symmetric [2]
- Peripheral arterial disease — chronic ischemic changes, absent pulses, claudication history
- Venous stasis dermatitis — chronic bilateral lower extremity edema and skin changes in dependent populations [10]
- Warm water immersion foot — exposure to water 15–32°C; white wrinkled plantar surfaces; resolves in 2–3 days with drying [2]
- Tropical immersion foot — warm water >22°C for >3 days; bright red, swollen feet with pitting edema; may have fever and lymphadenopathy [2]
- Pressure necrosis — can mimic or coexist with immersion injury [2]
- Diabetic neuropathy/foot — chronic, associated with ulceration at pressure points
9. Past Medical History
- Prior episodes of NFCI or frostbite (increases susceptibility) [12]
- Peripheral vascular disease, diabetes, Raynaud phenomenon
- Venous insufficiency, lymphedema [8]
- Psychiatric illness, substance use disorders [3][10]
- Immunosuppression (increases infection risk)
- Tetanus vaccination status [2]
10. Physical Exam
Findings depend on the stage of injury at presentation: [1-2][5]
- Stage 1 (During exposure): Feet pale/white, cold, numb; diminished peripheral pulses; loss of proprioception [2]
- Stage 2 (Post-exposure/Prehyperemic): Mottled, cyanotic appearance; feet remain cold and numb; may have mild edema [5]
- Stage 3 (Hyperemic): Erythematous, warm, swollen feet; intense pain; full pulses with brisk capillary refill; possible blistering or tissue loss [5]
- Stage 4 (Posthyperemic): Chronic cold sensitivity, persistent neuropathic pain, cyanosis with cold exposure [5]
Key exam maneuvers:
- Palpate dorsalis pedis and posterior tibial pulses
- Assess capillary refill, skin temperature, sensation (light touch, pinprick, proprioception)
- Inspect for maceration, bullae, ulceration, necrosis, fungal infection
- Check for signs of cellulitis, lymphangitis, lymphadenopathy
- Assess core temperature to rule out concurrent hypothermia [4]
11. Lab Studies
- No specific labs are diagnostic — NFCI is a clinical diagnosis [1-2]
- If infection suspected: CBC, CRP/ESR, blood cultures, wound culture
- BMP — assess renal function, electrolytes (especially if hypothermic)
- Glucose — screen for diabetes in at-risk populations
- Lactate — if concern for sepsis
- CK — if concern for rhabdomyolysis from prolonged immobility
- Prealbumin/albumin — assess nutritional status in malnourished patients
12. Imaging
- Imaging is generally unnecessary for uncomplicated NFCI [1]
- Plain radiographs — if concern for osteomyelitis or foreign body
- Duplex ultrasound — if concern for DVT (prolonged immobility) or arterial insufficiency
- MRI — rarely needed; may help assess deep tissue involvement in severe cases
- Unlike frostbite, Tc-99m scintigraphy and MRA are not routinely indicated for NFCI [4]
13. Special Tests
- Nerve conduction studies / EMG — may be useful in chronic cases to document peripheral neuropathy; not needed acutely [12]
- Ankle-brachial index (ABI) — if concern for concurrent PAD
- Point-of-care ultrasound — assess for DVT if prolonged immobility
- No validated scoring system specific to NFCI severity exists
14. ECG
- Obtain ECG if concurrent hypothermia is suspected [4]
- Look for Osborn (J) waves, bradycardia, prolonged QT, atrial fibrillation — hallmarks of hypothermia
- Not routinely indicated for isolated immersion foot without systemic hypothermia
15. Assessment
Immersion foot is a peripheral vasoneuropathy resulting from prolonged cold-wet exposure causing intense vasoconstriction and ischemia-reperfusion neurovascular damage. [8][12] Key clinical pearls:
- Clinical diagnosis based on exposure history + characteristic staged progression [1-2]
- Tissue loss from NFCI alone is rare — necrosis usually indicates concomitant pressure injury or infection [1]
- Bilateral, symmetric involvement is typical; unilateral presentation should raise concern for infection or alternative diagnosis [2]
- Chronic sequelae (cold sensitivity, neuropathic pain) may persist for months to years and can be severely debilitating [2]
16. Treatment Plan
Initial management
- Remove from cold/wet environment; remove wet footwear and socks [5]
- Gradual, passive rewarming — allow feet to rewarm at room temperature; do NOT actively rewarm (no warm water baths) [1][4]
- Elevate affected extremities [2]
- Keep feet open to air or lightly dressed with loose dressings — avoid constriction [2]
- Gentle drying; avoid rubbing or massage
Pain management (stepwise)
- NSAIDs (ibuprofen) — first-line for mild pain [5]
- Amitriptyline 50–100 mg PO QHS — most effective for NFCI neuropathic pain; initiate early [1-2]
- Gabapentin — add if amitriptyline alone is insufficient [2]
- Opioids — for severe acute pain not controlled by above [5]
Infection management
- Wound care for any skin breakdown; tetanus prophylaxis if skin integrity compromised [2]
- Antibiotics if secondary cellulitis or infection develops [8]
Prevention counseling
- Change into dry socks at least daily [1-2]
- Avoid constricting footwear; stay active to promote circulation [2]
- Adequate nutrition and hydration [2][8]
- Regular foot inspection [2]
17. Disposition
- Discharge — mild cases (Stage 1–2) with intact skin, no infection, adequate social support, and ability to keep feet warm and dry [5]
- Observation/Admission — significant edema, blistering, skin breakdown, signs of infection, inability to ambulate, or concern for concurrent hypothermia
- Admission — tissue necrosis, gangrene, cellulitis/sepsis, severe pain requiring IV analgesia, or patients unable to care for themselves (homeless without shelter access) [3][9]
- Surgical consultation — if necrosis, compartment syndrome, or potential need for debridement/amputation [9][14]
- Social work consultation — for homeless patients to arrange shelter, dry footwear, and follow-up [11][15]
18. Follow Up / Return Precautions
- Follow-up in 2–3 days for wound check and reassessment of pain control
- Chronic neuropathic pain and cold sensitivity may persist for months to years — arrange outpatient pain management and neurology referral if needed [2][12]
- Return precautions: worsening pain, new skin breakdown or blistering, fever, spreading redness, foul-smelling drainage, inability to bear weight, or signs of systemic illness
- Counsel on increased vulnerability to future cold injury — prior NFCI significantly raises risk of recurrence [12]
- Expected recovery: mild cases resolve in days; severe cases may take weeks, with potential for long-term neuropathic sequelae [2]
References
1. Nonfreezing Cold Injury (Trench Foot). — Zafren K. International Journal of Environmental Research and Public Health. 2021.
2. Prevention and Treatment of Nonfreezing Cold Injuries and Warm Water Immersion Tissue Injuries: A Supplement to the Wilderness Medical Society Clinical Practice Guidelines. — Zafren K, Hollis S, Weiss EA, et al. Wilderness & Environmental Medicine. 2023.
3. Immersion Foot: A Case Report. — Olson Z, Kman N. The Journal of Emergency Medicine. 2015.
4. Hypothermia and Cold Weather Injuries. — Rathjen NA, Shahbodaghi SD, Brown JA. American Family Physician. 2019.
5. Heat and Cold Illness in Travelers. — Howard D. Backer and Luanne Freer CDC Yellow Book. 2025.
6. National Athletic Trainers' Association Position Statement: Environmental Cold Injuries. — Cappaert TA, Stone JA, Castellani JW, et al. Journal of Athletic Training. 2008.
7. American College of Sports Medicine Position Stand: Prevention of Cold Injuries During Exercise. — Castellani JW, Young AJ, Ducharme MB, et al. Medicine and Science in Sports and Exercise. 2006.
8. A Review of Trench Foot: A Disease of the Past in the Present. — Mistry K, Ondhia C, Levell NJ. Clinical and Experimental Dermatology. 2020.
9. A Case of Bilateral Trench Foot. — Parsons SL, Leach IH, Charnley RM. Injury. 1993.
10. Infections in the Homeless. — Raoult D, Foucault C, Brouqui P. The Lancet. Infectious Diseases. 2001.
11. Health Care of People Experiencing Homelessness: Part I. — Taylor SN, Munson D. NEJM Evidence. 2023.
12. ACSM Expert Consensus Statement: Injury Prevention and Exercise Performance During Cold-Weather Exercise. — Castellani JW, Eglin CM, Ikäheimo TM, et al. Current Sports Medicine Reports. 2021.
13. Preventing and Treating Trench Foot: Validation of an Educational Manual for Military Personnel. — Mendes B, Salomé GM, Pinheiro FAM, et al. Journal of Wound Care. 2018.
14. Recent Cases of Trench Foot. — Ramstead KD, Hughes RG, Webb AJ. Postgraduate Medical Journal. 1980.
15. Foot Conditions Among Homeless Persons: A Systematic Review. — To MJ, Brothers TD, Van Zoost C. PloS One. 2016.