Trench foot: what it is, symptoms, treatment and prevention

Patient.info's professional reference, written for UK doctors, defines trench foot as a non-freezing injury of the hands or feet resulting from chronic exposure to wet conditions and temperatures just above freezing. It places it within a broader group called non-freezing cold injury, a clinical syndrome that occurs as a result of exposure to low temperature over a long time without freezing of tissue fluids.

It is different from frostbite. The NHS says frostbite happens when your skin freezes after being in very cold temperatures, and that you can get it if your skin is exposed to temperatures of 0C (32F) or below. In trench foot the tissue does not freeze; the injury follows prolonged exposure to cold and wet.

Patient.info's professional reference says that during exposure the body part first feels cold, then numb, with individuals describing clumsiness alongside loss of sensation. The entire foot may appear black but deep tissue destruction may not be present.

The painful phase follows. The reference describes progression to hyperaemia (increased blood flow) within 24 to 48 hours, causing intensely painful burning and abnormal sensation, with tissue damage causing swelling, blistering, redness, bruising and ulceration. Complications include local infection, cellulitis, lymphangitis or gangrene.

• Cold, numb, clumsy feet with reduced feeling.

• Intense burning pain and pins and needles once the feet warm up.

• Swelling, redness, bruising and blistering.

• Skin breakdown or ulcers, which can become infected.

• In severe cases, signs of tissue death such as black, hard skin.

Patient.info's professional reference says that for non-freezing cold injury, gradual rewarming is the first stage of treatment, and affected extremities should not be rubbed. It says analgesia may be required, that pain may be relieved by tricyclic antidepressant treatment, that a pain specialist may be needed to advise about pain relief, and that in later stages a specialised foot service may help with insoles and footwear advice. It lists tetanus prophylaxis if indicated among additional areas to consider.

The NHS frostbite page gives a useful general principle for any cold-injured body part: go indoors or somewhere sheltered, remove wet or constricting items such as boots and rings, do not rub the area, and do not use a fire, radiator, hot water bottle or heat lamp to warm it. It suggests placing the body part in warm (not hot) water, drying it, putting on a light dressing, and raising it to reduce swelling.

There is no specific NHS page for trench foot. The NHS frostbite advice says to call 999 or go to A&E if you have been exposed to very cold temperatures and have hard, frozen skin, swelling and loss of feeling, blisters filled with blood or clear or milky fluid, or if you are constantly shivering, have slurred speech, slow breathing and are tired and confused, which can suggest hypothermia.

For milder cold damage, the NHS chilblains page says to see a GP if skin is not getting better after 2 to 3 weeks, if there is pus coming out of the skin, if your temperature is very high or you feel hot, cold or shivery, if you keep getting chilblains, or if you have diabetes because foot problems can be more serious. Trench foot is more severe than chilblains, so persistent numbness, severe pain, blistering or skin breakdown after cold, wet exposure is a reason to ask NHS 111 or a GP for advice.

Patient.info's reference defines trench foot as a non-freezing injury resulting from chronic exposure to wet conditions and temperatures just above freezing. It describes non-freezing cold injury as occurring after exposure to low temperature over a long time without freezing of tissue fluids.

It lists factors that increase susceptibility to cold injury generally: lower temperatures, especially windy conditions, dehydration, extremes of age, malnutrition and exhaustion, immobilisation, prolonged exposure, moisture and peripheral arterial disease. Smoking, diabetes and Raynaud's disease increase risk due to vasoconstriction, and body parts previously injured by cold are at increased risk.

Patient.info's professional reference lists open wounds, secondary wound infection, tetanus and gangrene among complications of cold injury, and says that when combined with hypothermia or wound-related sepsis, localised cold injuries may lead to death.

It lists possible long-term effects of cold injury: increased sensitivity to cold that persists in the long term, vasospasm, hyperhidrosis or anhidrosis (excessive or absent sweating), joint stiffness, and others. The NHS says frostbite can cause the skin and tissue to die (gangrene), which may mean the affected body part needs to be amputated, and that some people have lasting problems such as pain and stiffness.

Patient.info's reference says proper attention to foot hygiene can prevent the occurrence of most such injuries. The NHS chilblains page advises avoiding being outside when it is cold or damp, wearing warm, waterproof clothing, gloves and thick socks if you do go out, and drying and slowly warming your skin if you have been exposed to cold.

The NHS frostbite page advises wearing several loose layers of clothing with a waterproof outer layer, a hat and scarf, gloves or mittens, and thick socks and boots, and eating and drinking regularly if you are in cold conditions for long periods. The NHS chilblains page says foot problems can be more serious if you have diabetes, so extra care applies to anyone with diabetes.

Trench foot is usually first assessed by a GP, NHS 111 or an urgent care or emergency department if it is severe, and, as the professional reference notes, people may later be referred to a specialised foot service or pain specialist. Frostbite, the related freezing injury, is treated in hospital according to the NHS.

If you consider a private foot or pain clinic for lasting symptoms, ask how your history of cold exposure will be taken into account, and how care will be shared with your GP.