Recurring hot and cold flashes happen when your body’s internal thermostat gets disrupted, and the causes range from hormonal shifts and stress to infections and medication side effects. The sensation isn’t random. Something is triggering your hypothalamus, the part of your brain that regulates temperature, to miscalculate whether you need to heat up or cool down. Figuring out which trigger applies to you depends on when the flashes happen, how long they last, and what else is going on in your body.
Hormonal Changes Are the Most Common Cause
If you’re in your 40s or 50s, fluctuating estrogen levels are the most likely explanation. Estrogen directly influences the hypothalamus, and when levels drop during perimenopause and menopause, your brain becomes hypersensitive to small changes in core body temperature. A shift of just a fraction of a degree can trigger a full-blown hot flash followed by chills as your body overcorrects.
Hot flashes peak in the year before your period stops and the year after. But they aren’t short-lived for everyone. Recent research shows hot flashes can continue for up to 14 years after menopause. That’s a much longer window than many people expect, and it means flashes that started years ago may still be hormonally driven even if menopause feels like old news.
Hormonal flashes aren’t exclusive to menopause. Low testosterone in men can produce similar episodes. So can thyroid disorders, particularly an overactive thyroid, which speeds up metabolism and throws off temperature regulation. Doctors sometimes check thyroid-stimulating hormone (TSH) levels alongside reproductive hormones like FSH and estradiol when evaluating unexplained temperature swings, because hyperthyroidism mimics menopausal symptoms closely enough to be mistaken for them.
Stress and Anxiety Can Trigger Temperature Swings
Your fight-or-flight system is a powerful and often overlooked source of hot and cold flashes. When you feel anxious or panicked, your body floods with adrenaline. That surge sends blood rushing to your muscles and increases circulation, which can make you feel suddenly hot, flushed, and sweaty. Once the adrenaline subsides, the rapid cooldown can leave you shivering.
This cycle is especially common in people with generalized anxiety, panic disorder, or chronic stress. The flashes tend to come on suddenly and pair with a racing heart, shallow breathing, or a sense of dread. If your hot and cold episodes line up with moments of worry or tension rather than appearing at random, stress hormones are a strong suspect. The pattern can also become self-reinforcing: the flash itself feels alarming, which triggers more anxiety, which triggers another flash.
Your Body Fighting an Infection
The classic chill-then-flush cycle during illness is your immune system at work. When you have an infection, your hypothalamus deliberately raises your body’s temperature set point to create a less hospitable environment for the invading pathogen. Before your core temperature reaches that new target, you feel cold, and your muscles contract and shiver to generate heat. Once your temperature hits the mark, the chills stop. Then, when the fever breaks (or you take fever-reducing medication), the set point drops back down and you suddenly feel hot and sweaty as your body dumps the excess heat.
This alternating pattern of chills followed by flushing is normal during acute illness. It becomes worth paying attention to if it keeps cycling over days without improvement, if fevers spike above 103°F, or if you can’t identify an obvious illness causing it.
Medications That Disrupt Temperature Control
Several common medications interfere with your body’s ability to regulate temperature, and the effect isn’t always obvious. Antidepressants are some of the biggest culprits. SSRIs and SNRIs can cause increased sweating and heat sensitivity, while older tricyclic antidepressants do the opposite, decreasing your ability to sweat and making it harder to cool down. Antipsychotic medications can impair both sweating and the brain’s central temperature regulation.
Stimulant medications used for ADHD, certain antihistamines, and diuretics (often prescribed for blood pressure) also affect thermoregulation. If your hot and cold flashes started or worsened after beginning a new medication, that timing is a meaningful clue. Don’t stop a prescription on your own, but it’s worth raising the connection with whoever prescribed it.
Autonomic Nervous System Problems
Your autonomic nervous system controls the behind-the-scenes functions you never think about: heart rate, blood pressure, sweating, and body temperature. When this system malfunctions, a condition broadly called dysautonomia, temperature regulation is one of the first things to go haywire.
One well-known form is postural orthostatic tachycardia syndrome (POTS), in which the blood vessels don’t tighten properly when you stand up. Blood pools in the lower body, and the resulting cardiovascular compensation can produce waves of heat, flushing, and chills. In neuropathic forms of POTS, damage to the small nerve fibers that control blood vessel constriction in the limbs and abdomen is the underlying problem. If your temperature swings come with dizziness when standing, a racing heartbeat, or fatigue that worsens with upright activity, dysautonomia is worth investigating.
Everyday Triggers That Make It Worse
Regardless of the root cause, certain daily habits reliably intensify hot and cold flashes. Caffeine is a common amplifier. It stimulates the nervous system and can directly provoke hot flashes and night sweats, creating an ironic cycle: poor sleep from night sweats leads to more caffeine, which leads to more flashes, which leads to worse sleep.
Alcohol increases both the frequency and intensity of hot flashes, particularly if you’re having more than one drink a day. Spicy foods raise your core temperature and can trigger an episode on their own. None of these cause the underlying problem, but cutting back on them is one of the few things you can control immediately while sorting out the bigger picture.
How Doctors Figure Out the Cause
There’s no single test for hot and cold flashes. Diagnosis usually starts with your pattern. Your doctor will want to know when the episodes happen (day, night, or both), how long each one lasts, whether they come with other symptoms, and what medications you’re on. Blood work can help narrow the field. FSH and estradiol levels indicate whether menopause is involved, though these hormones fluctuate enough during perimenopause that a single test isn’t always conclusive. TSH levels rule thyroid dysfunction in or out. Additional testing depends on what your symptoms suggest.
For hormonally driven flashes, treatment options have expanded. Hormone therapy remains the most effective approach for menopausal hot flashes, and newer non-hormonal options now exist. One recently approved medication works by blocking a specific brain receptor involved in thermoregulation and reduced both the severity and frequency of hot flashes by half in clinical trials. For flashes driven by anxiety, addressing the anxiety itself through therapy, stress management, or medication adjustments typically resolves the temperature swings as a byproduct.
The key distinction is whether your flashes are an isolated nuisance or part of a larger pattern. Flashes paired with an irregular heartbeat, unexplained weight changes, persistent fatigue, or dizziness point toward a systemic cause that benefits from workup. Flashes that track cleanly with stress, menstrual cycle changes, or a known medication are easier to address directly.