what causes hot flashes at 21???

Answer 1

Niacin. The flu. Standing too close to an open oven.

Answer 2

It could be several sources. It could be a hormonal imbalance, an undiagnosed health problem, and there are numerous medications which are known to cause flushing of the skin. Several medication inserts, or medication books will tell you that a medication can cause such symptoms that you should "not be exposed to prolonged sunlight," due to the fact that the med causes reduced sweating, and other symptoms.
The first thing you should do is have a complete physical to rule out any medical problem and discuss the "hot flashes" with your primary care physician, to see if any referral or medication adjustments may be necessary. Good Luck!

Answer 3

A diminished level of estrogen has a direct effect on the hypothalamus, the part of the brain responsible for controlling your appetite, sleep cycles, sex hormones, and body temperature. Somehow (we don't know how), the drop in estrogen confuses the hypothalamus—which is sometimes referred to as the body's "thermostat"—and makes it read "too hot."

The brain responds to this report by broadcasting an all-out alert to the heart, blood vessels, and nervous system: "Get rid of the heat!" The message is transmitted by the nervous system's chemical messenger, epinephrine, and related compounds: norepinephrine, prostaglandin, serotonin. The message is delivered instantly. Your heart pumps faster, the blood vessels in your skin dilate to circulate more blood to radiate off the heat, and your sweat glands release sweat to cool you off even more.

This heat-releasing mechanism is how your body keeps you from overheating in the summer, but when the process is triggered instead by a drop in estrogen, your brain's confused response can make you very uncomfortable. Some women's skin temperature can rise six degrees Centigrade during a hot flash. Your body cools down when it shouldn't, and you are miserable: soaking wet in the middle of a board meeting or in the middle of a good night's sleep.