What is a hot flash?

A hot flash (or hot flush) is a sudden sensation of intense heat, typically in the upper body and face, often accompanied by flushing, sweating, and sometimes a rapid heartbeat or feeling of anxiety. It lasts anywhere from 30 seconds to 10 minutes, and is followed by chills as the body overcorrects. When they happen at night and disrupt sleep, they're called night sweats.

Hot flashes are the most commonly reported menopause symptom. Around 75% of people going through menopause experience them, and for approximately 25% they are severe enough to significantly affect quality of life.

What's actually happening

Hot flashes are caused by changes in the hypothalamus — the part of the brain that regulates body temperature. During perimenopause, declining and fluctuating oestrogen levels affect the hypothalamus's thermoregulatory function. The thermoneutral zone — the range of body temperatures the hypothalamus considers normal — becomes narrow. Small increases in core temperature that would otherwise go unnoticed trigger a heat-dissipation response: vasodilation, sweating, increased heart rate.

It's not that you're actually overheating. Your body is responding to a perceived temperature change that isn't there. The result is a very real physical experience triggered by a calibration problem.

Known triggers

Hot flashes can be triggered or worsened by a range of factors:

• Heat — hot weather, warm rooms, hot drinks, hot showers
• Spicy food
• Alcohol, particularly red wine
• Caffeine
• Stress and anxiety
• Tight clothing or synthetic fabrics

Triggers vary significantly between individuals — what reliably causes flashes in one person may have no effect in another. Logging flashes with the context (time of day, what you ate and drank, stress level, ambient temperature) is the most reliable way to identify your personal triggers.

How long do they last?

Hot flashes typically begin in perimenopause and continue for several years after the final period. The median duration is around 7 years, though some people experience them for over a decade. Frequency and intensity usually peak around the time of the final period and gradually decrease in postmenopause — but this pattern is highly variable.

If hot flashes are severely affecting sleep, work, or daily life, that's a reasonable basis for discussing treatment options with a GP. Effective treatments exist — including HRT and non-hormonal options — and the impact on quality of life is a legitimate clinical consideration.