If a body temperature of 107 degrees Fahrenheit is fatal, what low body temperature is generally fatal?

Medical literature contains few if any cases in which people have recovered after their inner, or core, temperatures dropped below 55 degrees Fahrenheit.

Core body temperature is usually measured by elec, tronic sensors inserted into the digestive tract. It cannot be measured with an ordinary oral thermometer. Hypothermia is considered to exist whenever the core temperature is below 95 degrees.

Hypothermia occurs when the body loses heat faster than it can burn fuel to replace it. How severe a person’s reactions to low temperatures will be depends on age and overall physical condition, with the very old and the very young the most vulnerable; about 80 percent of hypothermia deaths occur in those older than 65.

Age increases the risk for several reasons. The ability to generate body heat declines because the heart rate is slower, blood vessels do not contract as well, and the elderly often lose muscle tone (which generates heat) and body fat (which conserves heat and supplies body fuel).

Exposed skin, cold air, cold water, cold wet clothing, and sitting on a cold surface that conducts heat away from the body all greatly increase the rate of heat loss. Dehydration also adds to the risks.

The rates of chemical activity in the body are slowed by very low temperatures. Eventually the heartbeat and breathing may stop, but even a very slow heartbeat and rate of respiration may maintain vital body functions.

Immediate treatment for hypothermia victims involves stopping further loss of heat by wrapping the person in warm, dry blankets.

Gentle handling is essential because jolts can cause fatally irregular heart rhythms. minimized by keeping out of tanning booths and direct sunlight at midday, routinely using sunscreen, covering arms and legs, and wearing a hat with a four-inch brim.

Treatment may involve bleaching or fading creams, which can take weeks or months; chemical peels; prescription drug treatments like tretinoin, a derivative of vitamin A, used with sunscreens; related over-the-counter products containing retinols; and surgical resurfacing, often with lasers, to remove the pigmented cells.