Introduction

Spending a long time in cold and wet conditions can cause health problems.^1,2 This article will cover two problems that can be caused by freezing conditions, namely trench foot and frostbite. 

Trench foot

This problem, also called Immersion Foot Syndrome, occurs when the body is exposed to cold and damp.³ This can make the capillaries (small vessels that carry your blood)⁴ constrict (get smaller) and dilate (get bigger).⁵ This can damage or even destroy the vessels.^1,5 This means that the flesh around these capillaries doesn’t have enough blood, causing damage.⁵

The skin damage can cause: skin breaking, blisters and sores on your feet.⁵ This means that there’s a higher risk of infection from bacteria and fungi.³ 

Trench foot usually affects the toes and/or heels, but it can cover the whole foot.⁵ If it is not treated, it can lead to gangrene.⁵

Cause of trench foot

Trench foot occurs when a person is somewhere that is cold (but not freezing) while their feet are wet.^1,3 It can happen in temperatures as high as 16°C and can begin as quickly as ten hours after the feet become cold and wet.¹ 

Symptoms of trench foot

The first symptom of trench foot is an itching or tingling feeling that gradually changes to numbness.⁵ The skin will often have red or blue patches on it (this may be easier to see in people with paler skin; patients with darker skin may struggle to notice changes like this).^1,5 

The feet may swell to as much as twice their normal size.^1,5 The skin may become extremely sensitive.^1,5 The foot may develop blisters and sores, and it may start to smell if the tissue gets damaged enough to start breaking down (this is called “necrosis”).^1,5 

If left for long enough, the trench foot may lead to gangrene or sepsis.^1,5 

Treatment for trench foot

Prevention

If possible, it is best to make sure that trench foot never happens.⁵

The best way to try and stop trench foot from becoming a problem is to:

• Avoid getting your feet wet and cold if possible³
• If your feet do get cold and wet, dry them and warm them as soon as you ca³
• Change your socks at least once a day, especially if you have become cold and wet³
• Do not continue to wear shoes that have got wet³
• Keep moving as this will encourage the blood to keep flowing to your feet³
• You can rub oil into the feet as this repels water³
• Check your feet regularly for signs of trench foot.³
• Make sure your footwear fits well, neither too tightly nor too loosely, to prevent damage to the foot¹ 

Early trench foot

As long as it is caught early, trench foot is treatable^.1

Doctors will slowly warm the feet back to a normal temperature.⁵ This can be very painful, so pain relief like amitriptyline may be needed.⁵

The foot should also be cleaned and kept dry and warm as it heals.⁵ Your health professional may also ask you to keep your feet raised above the level of your heart, as this can help to stop blisters from forming.¹

You may be prescribed antibiotics to stop any infection.¹

Advanced trench foot

If the trench foot has become bad enough that gangrene has set in, surgery may be needed to remove the damaged tissue.⁵ It is very rare for trench foot to progress this far.⁵

Risk factors for trench foot

Some people are more likely to develop trench foot than others.^{1, 3} Some things that make trench foot more likely are:

• Smoking. Nicotine can reduce the amount of blood that flows to your feet, making trench foot more likel¹
• Malnutrition (a condition that can happen if the food you eat does not have enough nutrients to keep you healthy)⁶ can make trench foot more likely³
• If your foot is already damaged, whether from a bump or cut, or due to an infection from bacteria or fungus, then you are more likely to get trench foot³
• If you have lymphoedema (a problem where your body swells due to not being able to drain enough fluid)⁷, you are at more risk of getting trench foot³
• If your blood vessels have difficulty bringing blood back to your heart (sometimes known as venous hypertension)⁵ this can mean that you are more likely to get trench foot³ 

Frostbite

Frostbite is the most common injury caused to humans by the cold⁸ 

Causes of frostbite

Frostbite happens when the body is damaged due to being in conditions of -0.55^oC or below.² In low temperatures, your body sends less blood to the hands and feet so it can send more to its important organs.² This reduction in the blood flow means that those parts of the body can get cold enough to freeze.² When the tissue freezes, ice crystals form and damage the flesh.²

Sometimes people do not know that they have frostbite.⁹ This is because frostbite makes the affected parts of the body go numb.⁹

Stages and symptoms of frostbite

Doctors have divided frostbite into three stages.⁹

Stage 1: frostnip

In this stage, the damage is reversible.⁹ Your skin may be red or purple (this is easier to see on people who have pale skin).⁹ You may also feel a tingling or slight pain.^{2, 9}

The skin may be painful as it goes back to a normal temperature, and you may get chilblains (small red spots) on your skin.⁹ 

Stage 2: superficial frostbite

At this stage, your skin may start to feel warm again, even though the tissue is freezing, causing ice crystals to damage your flesh.⁹ Your skin may swell, or sting, and you might feel a “pins and needles” sensation.⁹

Once you are warm again, the skin might be covered in blue-purple marks like bruises, it may feel sunburned, and it could blister.⁹

Stage 3: severe frostbite

This happens when the deeper layers of the skin freeze.⁹ Because the affected area is frozen, it may be difficult to move that part of your body.⁹ The area will usually be numb, and the colour of the skin will change to black due to the skin dying.⁹ This black area may fall off after a while.⁹

Treatment of frostbite

Prevention

If you can, it is best to prevent frostbite from happening in the first place.² You can avoid frostbite by:

• Avoid going outside in freezing temperatures if you can²
• Don’t stay in the same place or position for long periods, as this may mean that blood doesn’t flow as well to some areas of your body⁸
• If you have to go out in freezing conditions, make sure you have all of the cold-weather gear that might be needed.⁸ Ideally, this should be several layers of loose, warm clothes to help build insulation² 
• Change quickly out of wet clothes into dry ones⁸
• Try to stay out of the wind⁸
• Undergo training on how to survive cold conditions⁸
• Wear mittens rather than gloves, as they help keep you warmer²
• Make sure your ears are protected²

Treatment

Your healthcare team will slowly warm up the affected area by placing it in a warm (not hot) bath.² The frostbitten person may have severe pain when this happens, so painkillers may be given.²

If the person has had frostbite for less than a day, your healthcare provider might treat you with iloprost,¹⁰ a drug which helps with blood flow by widening the blood vessels.¹¹ Frostbite can also cause your blood to clot, which can block your blood vessels and make it even harder for blood to reach the affected parts of the body.¹² Your medical team may give you tissue plasminogen activator (tPA),¹² which helps to dissolve blood clots¹³ and can mean that the body will heal more effectively.¹² 

Sometimes the frostbitten area cannot be saved and must be removed by surgery.¹² 

Risk factors for frostbite

Some things make a person more likely to get frostbite.² Some of these are:

• Smoking, as this makes the blood vessels get narrower²
• Taking medications that narrow the blood vessels, for example, beta blockers²
• Spending time in winter environments for work or sport²
• People who have problems with their blood flow, for example, if they have Raynaud’s disease or diabetes²
• People who are homeless and so may not be able to get out of the cold²
• Infants and the elderly, as young and old bodies, have more trouble controlling their temperatures²

Differences between trench foot and frostbite

Though they are similar in some ways, there are several key differences between these two conditions.

• Trench foot happens in temperatures above freezing; frostbite happens in conditions that are below freezing
• Trench foot only happens when it is cold and wet. Frostbite can happen without dampness
• Trench foot is thought to be caused by damage to the capillaries that supply the feet with nutrients. Frostbite happens when the skin and the tissue beneath it freeze, meaning that ice crystals in the flesh cause damage to the body

Summary

Both trench foot and frostbite are treatable if caught early. It is important to get help from a medical professional as soon as possible if you think that you or someone you know has either problem, due to the risk of severe problems if it is not managed quickly.

Though they can appear similar, trench foot and frostbite are two distinct conditions.