Hot flash

A hot flash is a sudden feeling of intense heat, often accompanied by sweating and a rapid heartbeat, and it typically lasts between two and thirty minutes. This vasomotor symptom is most commonly linked to the hormonal shifts of menopause and is the most well-known sign of that transition. When these episodes last longer, they are often referred to as hot flushes.

The sensation of heat usually starts in the face or chest, though it can begin elsewhere, like the back of the neck, and may spread across the entire body. Some people feel faint during an episode. The skin, especially on the face, becomes hot to the touch, which is why the term "hot flush" is used—the heat often causes visible facial reddening. Hot flashes can occur a few times a week or as often as every few minutes throughout the day. They may start several years before menopause and continue for years afterward. Not everyone going through menopause experiences them; some have mild or infrequent flashes, while others have dozens daily. Hot flashes tend to be more frequent and intense in hot weather or a warm room, as surrounding heat can trigger or worsen them.

Severe hot flashes can disrupt sleep, leading to insomnia, which may affect mood, concentration, and cause other physical issues. When they happen at night, they are called night sweats. Because estrogen levels are typically lowest at night, some people have night sweats without daytime hot flashes. About one-third of women experience night sweats alone, and another third have them alongside hot flushes.

In younger women, hot flashes can occur at other points in the menstrual cycle and may signal a pituitary gland problem. For those who undergo surgical menopause, hot flashes are often more intense than in older women and may last until the natural age of menopause. In men, hot flashes can result from low testosterone, prostate or testicular cancer, or hormone therapy that reduces testosterone to castrate levels. Castrated men may also experience them. Intersex individuals can have hot flashes during hormonal shifts, or after surgeries like postpubertal orchiectomy if they do not receive supplemental hormones to replace lost hormone production.

Some menopausal women experience two types of hot flashes. The standard type comes on rapidly, sometimes peaking within a minute, and lasts at full intensity for only a few minutes before fading. The second type, called "slow hot flashes" or "ember flashes," appears almost as quickly but is less intense and lasts about half an hour. These may occur year-round and can linger for years after more intense flashes have stopped.

Research on hot flashes focuses mainly on treatment, and the exact cause of vasomotor symptoms is not fully understood. They are linked to declining estrogen levels, estrogen withdrawal, and other hormonal changes, but low estrogen alone is not the sole cause—women with hot flashes have similar plasma estrogen levels to those without them, and prepubertal girls do not have hot flashes despite low estrogen. There are signs that hot flashes may stem from changes in the hypothalamus's temperature regulation. Transgender men also commonly report hot flashes, linked to hormonal changes from masculinizing hormone therapy, such as puberty blockers, oophorectomy, or long-term testosterone use reducing estradiol production.

Hormone replacement therapy (HRT) can relieve many menopausal symptoms, but oral HRT may increase risks of breast cancer, stroke, and dementia, among other serious side effects. Recent studies suggest that transdermal estradiol applications may offer vascular benefits and lower cardiovascular risks with fewer adverse effects than oral preparations. Women with troublesome hot flashes may try alternative treatments.