It feels like heat in the upper body or even the whole body. The woman's upper body or face often turns red, or get red blotches. She may sweat and then shiver as her body returns to a normal temperature. Hot flashes can appear at any time, day or night. The hot flash may last only seconds, or may last up to half an hour.
Hot flashes are a result of decreasing estrogen levels.
As estrogen levels decline, the body releases other hormones. These can cause the fluctuations in body temperature. As women get closer to menopause, the risks of osteoporosis , or bone thinning, and heart disease increase. Lower estrogen levels may be part of the Reason that these risks increase. There is no prevention for perimenopause.