Cold-weather warfare
Trench foot is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions at temperatures as warm as for as few as 13 hours. Exposure to these environmental conditions causes deterioration and destruction of the capillaries and leads to morbidity of the surrounding flesh. Affected feet may become numb, affected by erythema (turning red) or cyanosis (turning blue) as a result of poor blood supply, and may begin emanating a decaying odour if the early stages of necrosis (tissue death) set in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections. If left untreated, trench foot usually results in gangrene, which may require amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when feeling returns. Trench foot affected tens of thousands of soldiers engaged in trench warfare in World War I. Keeping feet warm and dry, or at least changing into warm and dry replacement footgear, is the best way to avoid trench foot.
Barefoot
Since there is no artificial protection of the bare foot, some of the possible issues include cuts, abrasions, bruises, or puncture wounds from glass, nails, rocks, or thorns, as well as poisonous plants, animals, or parasites that can enter the body through the cuts on an injured bare foot. In people who are not habitually barefoot, Athlete's foot is spread by fungal spores coming into contact with skin that has been weakened and made moist. The fungus is known to only affect around 0.75% of habitually barefoot people in one study and can be prevented by reducing shoe use and keeping the feet dry, particularly after walking through a damp environment where people communally walk barefoot as the fungus only develops under the right conditions, such as when people fail to properly dry their feet after swimming or showering and then put on shoes. Wearing shoes such as flip flops or sandals in these areas can reduce the risk. As such, the fungus is very unlikely to develop on a person who goes barefoot all the time.