Sweating and Dysautonomia: Too Much, Too Little, and Night Sweats

If your sweating has gone strange since developing POTS, long COVID, or another form of dysautonomia, there is a clean physiological reason, and it is not that you are unfit or anxious. Sweating is run entirely by your autonomic nervous system. So when that system is dysregulated, your sweating very often is too, and, confusingly, it can go in either direction: too much for some people, too little for others, and a patchy mix for many. This article explains the wiring behind autonomic sweating, walks through the common patterns in dysautonomia, and lays out how to read your own without spiraling.

These are educational field notes, not medical advice. Nothing here diagnoses or treats anything. Sweating has plenty of causes outside the autonomic nervous system, so any sudden, drenching, or one-sided change is worth taking to a clinician.

How sweating is wired to your nervous system

Your sweat glands do not decide anything on their own. The eccrine glands that cover most of your body, and do nearly all of your temperature-regulating sweating, are switched on by nerves from the sympathetic branch of the autonomic nervous system, the same branch behind the “fight or flight” response. The command starts in the hypothalamus, your brain’s thermostat, which senses core temperature and stress signals, and runs down through the spinal cord and out along small sympathetic nerve fibers to the skin.

There is one genuinely odd detail that explains a lot. Most sympathetic nerves release noradrenaline at their target, but the sympathetic fibers going to eccrine sweat glands are the exception: they release acetylcholine, the same messenger the parasympathetic system usually uses. That is why these are sometimes called “sympathetic cholinergic” fibers, and it is why anticholinergic medications (which block acetylcholine) can reduce sweating so effectively.

Two things follow from this diagram, and they map onto the two directions dysautonomia can take. Turn the pathway up (more sympathetic drive, more adrenaline in circulation) and you get more sweating. Damage the pathway (the small fibers that carry the signal degrade) and you get less. Many people with dysautonomia have some of both happening in different places, which is exactly why the picture can look contradictory. For the bigger map of how these branches work, the autonomic nervous system and dysautonomia guide is the place to start.

Too much: hyperhidrosis and adrenaline-driven sweats

The most common complaint in dysautonomia is sweating that feels excessive or badly timed. A few distinct flavors show up:

• Generalized overactivity. In hyperadrenergic POTS in particular, circulating noradrenaline runs high, and the whole sympathetic system, including the sweat pathway, sits closer to its trigger point. Standing, mild exertion, a warm room, or stress can set off sweating that seems out of proportion. This often travels with tremor, palpitations, and a cold, clammy feel to the hands and feet. The hyperadrenergic POTS overview covers that subtype in detail.
• Adrenaline surges. A sudden catecholamine release, what many patients call an “adrenaline dump,” produces a burst of cold or drenching sweat alongside a racing heart, shakiness, nausea, and a sense of dread. These can hit at rest and at night. We cover the mechanism and how to ride them out in adrenaline dumps in POTS.
• Presyncopal cold sweat. Just before a faint, blood pressure drops and the body throws out a pale, clammy sweat. This one is a warning sign to sit or lie down, not a thermoregulatory sweat at all.

Not all excess sweating is dysautonomia, and it is worth keeping that in view. Thyroid overactivity, menopause, infection, low blood sugar, anxiety states, and several medications all cause sweating too. If sweating is your main new symptom, that broader list deserves a look before you file it under “autonomic.”

Too little: hypohidrosis, anhidrosis, and heat intolerance

The opposite problem is less talked about but just as real. When the small nerve fibers feeding the sweat glands are damaged, sweating drops. Hypohidrosis is reduced sweating; anhidrosis is its near-absence. It can be patchy, often starting in the feet and legs and moving up, or widespread.

The usual culprit in POTS and long COVID is small fiber neuropathy, damage to the same thin nerves that carry the sudomotor signal (and pain and temperature sensation). A meaningful fraction of people with these conditions have been found to have small fiber involvement on skin biopsy, and reduced distal sweating is one of its fingerprints. Our deeper piece on small fiber neuropathy in POTS and long COVID walks through how it is found and what it means.

The practical risk of reduced sweating is heat intolerance. Evaporating sweat is your main way of shedding heat, so if that route is impaired, your core temperature climbs faster in warm conditions and you tire, flush, or feel unwell sooner. This is why so many people with dysautonomia describe wilting in the heat, and it links tightly to the patterns in heat intolerance and POTS.

The patchy middle: compensatory sweating and gustatory sweating

Real bodies rarely sit cleanly at one extreme. A very common pattern is compensatory hyperhidrosis: when some regions cannot sweat (say, the legs and trunk after nerve damage), the areas that still work, often the face, scalp, and upper body, overcompensate and sweat heavily. It can look like a sweating “problem” when the underlying issue is actually too little sweating elsewhere.

Gustatory sweating, facial or scalp sweating triggered by eating (especially spicy or sour food), is another autonomic quirk that turns up in some forms of autonomic neuropathy. And plenty of people simply have an uneven map, sweating buckets from the hands while the shins stay dry. None of this is you doing something wrong; it is the sudomotor system misfiring in a spatial pattern.

A quick guide to the patterns

Sweating alone does not name a diagnosis. The pattern is a clue that points toward the fuller autonomic picture, which is assembled from your symptoms, orthostatic testing, and, where relevant, dedicated sweat testing.

Night sweats: sometimes autonomic, often not

Night sweats are one of the most searched sweating symptoms, and they are genuinely worth being careful with. Nighttime sympathetic activation and adrenaline surges can produce sweating and awakenings in POTS and long COVID, and disrupted, sympathetically driven sleep is a common thread through dysautonomia (we cover the sleep side in sleep and autonomic recovery).

But drenching night sweats have a long list of non-autonomic causes that matter: thyroid disease, menopause and perimenopause, infections, low overnight blood sugar, sleep apnea, some medications and antidepressants, and, less commonly, conditions that need prompt evaluation. So treat night sweats as a symptom to characterize, not to assume. New or heavy night sweats, especially with fever, unexplained weight loss, or one-sided symptoms, should be seen by a clinician.

Where sweat testing fits

If a clinician wants to measure your sudomotor function directly, a few tests exist, usually in an autonomic lab as part of a broader workup (see what to expect from autonomic function tests):

• QSART (quantitative sudomotor axon reflex test): a small stimulus is applied to the skin and the resulting sweat output is measured at several sites, mapping how well the postganglionic sudomotor nerves respond.
• Thermoregulatory sweat test (TST): the whole body is gently and safely warmed while an indicator powder changes color where you sweat, producing a map of which regions do and do not sweat.
• Sympathetic skin response: a simpler electrical measure, sometimes done during nerve conduction studies.

These are how reduced sweating is confirmed and localized. You cannot diagnose it from symptoms, which is exactly why testing exists.

How to track your own sweating pattern

You do not need a lab to start reading your pattern. The goal is to turn a vague “I sweat weird now” into something specific enough to act on and to bring to an appointment:

• Note when and where. Drenching-with-standing, cold-sweat-at-night, and dry-and-overheating are three different stories. Where on your body it happens matters too.
• Tie it to context. Heat, exertion, meals, stress, poor sleep, and your cycle all shift sweating. A simple symptom and trigger journal surfaces the links.
• Watch it beside your other autonomic signs. Sweating rarely travels alone. Reading it next to your heart rate, HRV trend, and stand-test numbers gives a much richer picture than sweating alone, and a rising sympathetic day often shows up in several of them at once.
• Scale fluids and salt to sweat loss. On heavy-sweat days, deliberately add fluids and salt; on low-sweat days, prioritize cooling.

The bottom line

Sweating is a direct readout of your autonomic nervous system, so in dysautonomia it commonly changes, in one direction or both. Too much sweating, from high sympathetic tone or adrenaline surges, is the frequent complaint, and it quietly drains the salt and fluid your blood volume depends on. Too little sweating, usually from small fiber nerve damage, is the quieter problem, and its real danger is overheating. Many people live in the patchy middle, with some areas overcompensating for others. None of these patterns is a diagnosis on its own; each is a clue. Characterize yours, replace what heavy sweating costs you, protect yourself from heat if you barely sweat, and bring the specifics to a clinician who can test and interpret them properly.