No one knows exactly what the physiologic cause is for hot flashes but the beginning trigger is probably increased heat (or blood flow) in the heat regulatory area of the brain.
The brain, sensing an increased body temperature, releases chemicals that cause the skin blood vessels to dilate so the heat can be released.
Apparently estrogens and testosterone allow the body to have a higher tolerance for changes in core body temperature. In other words, normally a body might tolerate a change in 1.5 degrees C. before dilating the blood vessels whereas in the absence of the sex hormones, the blood vessels are triggered to dilate at a change of only 0.8 degrees C.
This means that anything increasing core body heat or even just the heat of increased blood flow at the brain's heat regulatory center will cause a hot flash. The hot flash will last or keep repeating as long as needed to dissipate the increased heat.
Even women who are menopausal can reduce by almost 50% the number of night sweats by dropping the evening bedroom temperature a few degrees cooler.
Can foods or drinks cause a hot flash?
Definitely yes. Almost everyone should be familiar with how a meal containing hot pepper (capsaicin) can cause a rapid out break of a hot sweat. In this case, the capsaicin directly stimulates nerve endings that affect and dilate the brain blood vessels.
Alcohol, other food additives and just eating a large meal itself can cause hot flashes. The truth is that we do not know all the different foods and additives and other ingested substances that can trigger this reaction.
Many prescription drugs such as anti-hypertensives and mood altering drugs such as anti-depressants or anti-anxiety medications can also cause hot flashes. Each prescription drug you are taking should be checked to see if hot flashes or night sweats are a known side effect.
Over-the-counter medications and supplements should also be examined for their side effect profile.
What other conditions or circumstances can cause hot flashes that are not "menopausal"?
Many systemic conditions can also produce flushing such as carcinoid syndrome, systemic mast cell disease, pheochromocytoma, medullary carcinoma of the thyroid, pancreatic islet-cell tumors, renal cell carcinoma, hyperthyroidism, neurological flushing, emotional flushing, and spinal cord injury.
These conditions are thought to secrete chemicals into the blood stream that can stimulate the nerves or blood vessels of the brain.