 Frostbite. Frostbite occurs when exposure to low temperatures causes freezing of the skin or other tissues. The initial symptom is typically numbness. This may be followed by clumsiness with a white or bluish color to the skin. Swelling or blistering may occur following treatment. The hands, feet, and face are most commonly affected. Complications may include hypothermia or compartment syndrome. People who are exposed to low temperatures for prolonged periods, such as winter sports enthusiasts, military personnel, and homeless individuals are at greatest risk. Other risk factors include drinking alcohol, smoking, mental health problems, certain medications, and prior injuries due to cold. The underlying mechanism involves injuries from ice crystals and blood clots in small blood vessels following fine diagnosis is based on symptoms. Severity may be divided into superficial first and second degree or deep third and fourth degree. A bone skin or MRI may help in determining the extent of injury. Prevention is through wearing proper clothing, maintaining hydration and nutrition, avoiding low temperatures, and staying active without becoming exhausted. Treatment is by re-warming. This should be done only when re-freezing is not a concern. Rubbing or applying snow to the affected part is not recommended. The use of eye-will-profen and tetanus-toxoid is typically recommended. For severe injuries pilot frost or thrombosiletics may be used. Surgery is sometimes necessary. Amputation, however, should generally be delayed for a few months to allow determination of the extent of injury. The number of cases of frostbite is unknown. Rates may be as high as 40 percent a year among those who mount near. The most common age group affected is those 30 to 50 years old. Evidence of frostbite occurring in people dates back 5,000 years. Frostbite has also played an important role in a number of military conflicts. The first formal description of the condition was in 1814 by Dominique Jean-Larry, a physician in Napoleon's army.