What Happens When You're in Subzero Weather?

When the human body is exposed to subzero weather, the brain activates a protective physiological response in an attempt to survive the harsh conditions. If wind chill becomes a factor or a human is exposed to dampness in subzero weather, the seriousness of the situation increases dramatically. Without proper clothing, exposure to subzero weather may result in what experts term freezing and nonfreezing injuries or the life-threatening condition known as hypothermia.

Risks

• Among the nonfreezing injuries humans are susceptible to from repeated exposure to cold temperatures are chilblains, an inflammation of the hands, feet or ears, and trench foot, a painful condition affecting the feet that results from prolonged exposure to cold and wet weather. Freezing injuries include frostnip and frostbite. Frostbite is more serious than frostnip. Frostbite may involve death to the tissue of the affected area, as well as permanent damage to the blood vessels. When only the top layers of skin freeze, the injury is termed frostnip.

Physiological Response

• The human body works to protect its most vital parts during prolonged exposure to subzero weather. Shivering, a response that activates and prompts muscles to create heat, is often the first defense. Blood flow to the extremities, as well the ears and nose, is reduced as a means of conserving crucial heat for internal organs. As a result, hands and feet -- especially fingers and toes -- chill more quickly and are more likely to suffer frostbite.

Hypothermia

• In the event of prolonged exposure to subzero weather, the cold penetrates the body more deeply as surface areas are chilled, resulting in a decrease in core body temperature. Hypothermia, a severe injury from the cold, results when the body's core temperature falls to dangerously low levels. Sensations of pain from the extreme cold give way to numbness, an indication that serious injury is imminent. If the core temperature continues to fall, the victim will likely experience drowsiness and reduced consciousness. The pupils of the eyes become dilated. Should the body temperature fall to around 68 degrees Fahrenheit, the heart may stop. At around 63 degrees Fahrenheit, brain function ceases and death occurs.

Wind and Water

• If the body is exposed to damp or windy weather in addition to subzero air temperature, the risk for injury increases. Wet conditions cause the body to lose heat more quickly. Furthermore, wind chill increases the effect of subzero weather on the body, causing hypothermia more quickly. The corneas of the eyes may be frozen by exposure to cold, strong winds without the use of eyewear.