Like any other medical symptom, a sudden drop in body temperature can have many causes, some of which are quite normal. For example, people typically experience a rapid drop in body temperature before sleep, and women experience a drop in temperature each month before menstruation begins. And everyone is familiar with the sudden drop in temperature after an illness, when a fever is said to "break." Other sudden drops in temperature, however, are not so harmless: These severe drops, known as hypothermia, require immediate medical attention. The most common cause of hypothermia is exposure to extreme cold, but certain drugs and medical conditions can also make your body temperature fall.
Cause of Hypothermia: Heat Loss
If you're exposed to cold, it's possible for your otherwise healthy body to lose heat faster than it can make more. This is most likely to happen if you're outside in extreme cold for a long time, especially if you're not dressed adequately for the cold, but it can also happen if something else causes your body to lose heat more quickly than usual. For example, if your body is wet, it will lose heat faster than when you're dry. Windy conditions will also speed up heat loss.
Cause of Hypothermia: Medical Conditions
Other times, the cause of hypothermia lies within the body itself. A part of the brain known as the hypothalamus is responsible for regulating your body's temperature. To do this, it receives signals from your nervous system indicating that your body is too hot or too cold, and in turn it sends out signals to the rest of your body to take action. For example, if you're cold, the hypothalamus directs your body to shiver or to constrict blood vessels to prevent heat loss. Certain medical conditions, such as spinal cord injuries or diabetes, can interfere with the body's ability to receive or send out these signals effectively. Without appropriate signals, hypothermia can result.
Cause of Hypothermia: Drugs and Medications
Certain drugs -- prescription or otherwise -- can interfere with the body's ability to regulate its own temperature. For example, drinking alcohol tends to cause your blood vessels to dilate, which can interfere with your nervous system's efforts to keep you warm by constricting those blood vessels. Even worse, when you drink alcohol and your blood vessels dilate, you may actually feel warm, even as your body is losing more heat than it can generate. This can mislead you into thinking everything is fine when it's not. Other drugs, such as narcotics, sedatives, and certain antidepressants and antipsychotics, can also interfere with your body's ability to regulate temperature.
What to Do
If you suspect hypothermia in yourself or a loved one, get medical attention as soon as possible, because treatment depends on the cause. If the cause is cold, you can take certain measures while you wait for help. The Centers for Disease Control and Prevention recommends getting the person to a warm place of shelter right away, removing any wet clothing, and warming him in any way available -- for example with dry blankets or even skin-to-skin contact with a warmer person. The CDC advises focusing on warming the person's central regions -- the chest, abdomen and head -- before the extremities.