Trench foot develops when your feet stay wet and cold for an extended period, typically at temperatures between 32°F and 59°F (0 to 15°C). It’s not caused by freezing, which is what separates it from frostbite. Instead, the combination of moisture and cool temperatures slowly damages blood vessels and nerves in your feet, even in conditions that might not feel dangerously cold.
The Conditions That Cause It
Two ingredients are required: prolonged wetness and cold that stays below about 60°F. Your feet don’t need to be submerged in water. Wet socks inside damp boots are enough. The longer your feet stay in those conditions without drying out, the greater the damage. Hours of exposure are generally needed, though the exact threshold varies from person to person depending on factors like circulation, footwear, and activity level.
The name comes from World War I, when soldiers stood for days in flooded trenches, but you don’t need a battlefield to get it. Hikers caught in multi-day rain, outdoor workers in wet conditions, people experiencing homelessness during cold and wet weather, and festival-goers spending days in muddy fields have all developed trench foot. Anyone whose feet stay wet and cool without a chance to dry off is at risk.
What Happens Inside Your Feet
When your feet are cold and wet for a long time, the small blood vessels constrict to conserve heat. That’s a normal response, but sustained constriction starves the tissue of oxygen and nutrients. The walls of those tiny blood vessels become damaged, and small clots can form inside them. Nerves in the feet, which depend on that same blood supply, also suffer direct cold damage. The result is a combination of vascular injury and nerve injury concentrated in the toes and soles.
When the feet are finally warmed and dried, blood rushes back in, and this “reperfusion” phase can actually cause additional tissue damage. It’s similar to what happens with other types of restricted blood flow: the return of circulation triggers inflammation that compounds the original injury. This is why the pain from trench foot often gets worse, not better, when you first warm up.
How Symptoms Progress
Trench foot doesn’t announce itself all at once. It moves through distinct phases, and recognizing the early signs is the difference between a full recovery and lasting damage.
In the first phase, while your feet are still cold and wet, they go numb. The skin looks pale or waxy, and your feet may feel heavy or stiff. Because numbness masks the damage happening underneath, many people don’t realize anything is wrong at this point. They assume their feet are just cold.
Once the feet begin to warm up, the second phase hits. This is when pain, tingling, and swelling set in, sometimes intensely. The skin may turn red or blotchy, and the feet become extremely sensitive to touch. Blisters can form. In moderate cases, this painful phase lasts days to weeks as circulation slowly recovers.
In severe cases, the skin can turn dark or bluish, open sores develop, and tissue begins to die. At that point the damage may be irreversible, and in the worst scenarios, amputation becomes necessary. These extreme outcomes are rare with prompt treatment but were common in wartime when soldiers couldn’t leave wet trenches for days on end.
Long-Term Nerve Damage
Even after the skin heals, nerve damage from trench foot can persist for months or become permanent. Cold sensitivity is one of the most common lasting effects. People who’ve had trench foot often find that their feet ache or tingle in cool weather long after the initial injury has resolved. Chronic pain, excessive sweating in the feet, and heightened sensitivity to pressure are also reported. The nerve damage and the damage to the tiny blood vessels that feed those nerves can be reversible or permanent depending on severity and how quickly treatment began.
How to Prevent It
Prevention comes down to keeping your feet dry or, when that’s not possible, giving them regular breaks from moisture. The CDC recommends cleaning and thoroughly drying your feet, changing into clean dry socks, and elevating bare feet when you sleep. If you’re in a situation where wet feet are unavoidable, like a long hike in rain or working outdoors in wet conditions, rotating between two pairs of socks and air-drying the unused pair is one of the most practical steps you can take.
Waterproof boots help but aren’t foolproof, since sweat alone can keep feet damp inside sealed footwear. Boots that breathe or periodic sock changes matter more than waterproofing alone. Avoid sleeping in wet socks. If your feet have been wet all day, take the socks off at night and let your feet air out completely. Nicotine constricts blood vessels and worsens the reduced circulation that drives trench foot, so smoking increases your risk.
What to Do If You Have Symptoms
If your feet have been wet and cold and you notice numbness, tingling, or skin color changes, the first step is to get them dry and gently warm. The CDC recommends soaking affected feet in warm (not hot) water for about five minutes, then drying them thoroughly. Elevate your feet to help reduce swelling. Don’t rub or massage the affected skin aggressively, and avoid direct heat sources like campfires or heating pads, which can burn tissue you can’t fully feel.
Mild cases caught early often resolve within days to weeks with consistent dry conditions and rest. If the skin is blistered, discolored, or the pain is severe, you need medical evaluation. Infection is a real risk in damaged tissue, and severe cases may require wound care and monitoring. After recovery, check your feet daily for signs of returning symptoms and continue wearing clean, dry socks until the skin and sensation have fully returned to normal.