Short answer: Hyperhidrosis is caused by an overactive signal from the nervous system to otherwise normal sweat glands. In more than 90% of people it is primary hyperhidrosis: it has no underlying disease, usually starts before age 25, and often runs in families. In the rest it is secondary, meaning another condition or a medication is driving the sweat. Below we explain both types, what science has found about the cause, and the everyday triggers that make it worse.
What is hyperhidrosis?
Hyperhidrosis means sweating far more than your body needs to cool down. It's not about hot weather or a hard workout. People with hyperhidrosis sweat through shirts in air-conditioned offices, drip onto paperwork and avoid handshakes. A large US survey estimated that about 4.8% of Americans, roughly 15.3 million people, live with it.
Doctors split it into two types, and the cause is completely different for each. That's why the first question is always: primary or secondary?
Primary hyperhidrosis: the most common cause
According to a review in American Family Physician, more than 90% of cases are primary. Primary hyperhidrosis isn't a symptom of another disease. It's a condition of its own, and it usually affects specific areas on both sides of the body:
- Underarms (axillary)
- Palms (palmar)
- Soles of the feet (plantar)
- Face and scalp (craniofacial)
Because it targets these areas, primary hyperhidrosis is also called focal hyperhidrosis. Typical signs include sweating that started in childhood or the teenage years, happens at least once a week, appears on both sides symmetrically, and stops while you sleep.
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What actually causes primary hyperhidrosis?
Here's the surprising part: the sweat glands themselves are normal. People with hyperhidrosis don't have bigger or more numerous eccrine sweat glands. The problem is the signal that switches them on.
1. An overactive nervous system
Sweating is controlled by the sympathetic nervous system, the same "fight or flight" system that handles stress. Nerves release the messenger acetylcholine, which tells the glands to produce sweat. In hyperhidrosis, that signal fires far more often and more strongly than needed, even when you're calm and cool.
2. Genetics
Hyperhidrosis runs in families. Up to two-thirds of patients report a relative with the same problem, according to the AAFP review. In July 2026, researchers at Johns Hopkins published a study in Science Advances showing that in some families, a gene variant "turns up the volume" on the nerve signals that stimulate sweating. It's one of the clearest pieces of evidence so far that the condition starts in the nervous system, not in the skin.
3. Stress and anxiety as amplifiers
Stress doesn't cause primary hyperhidrosis on its own, but it pours fuel on it. Stress raises cortisol and puts the sympathetic system on alert, which is exactly the system that is already overactive. Then the sweating itself becomes a source of anxiety. In a study of more than 2,000 dermatology patients, anxiety was nearly three times as common in people with hyperhidrosis (21.3% vs 7.5%). The result is a loop: sweat, worry, more sweat.
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Secondary hyperhidrosis: when something else is the cause
Secondary hyperhidrosis is driven by another condition or a medication. It's much less common, but it's important to recognise because the cause itself needs attention. The AAFP review lists these among the most common causes:
- Hormonal changes: menopause and hot flashes
- Thyroid and metabolism: an overactive thyroid (hyperthyroidism), diabetes and low blood sugar (hypoglycemia)
- Infections and fever: including tuberculosis
- Heart and lung conditions: such as congestive heart failure
- Neurological conditions: including Parkinson's disease and spinal cord injury
- Anxiety disorders: generalised and social anxiety
- Alcohol and substance withdrawal
- Rare tumours: such as pheochromocytoma and carcinoid tumours
Medications that can cause sweating
Some common medicines list excessive sweating as a side effect, including:
- Antidepressants, especially SSRIs such as fluoxetine and SNRIs such as venlafaxine
- Diabetes medicines such as insulin and sulfonylureas
- Hormone-related drugs such as tamoxifen and raloxifene
- Others, including niacin and sildenafil
Primary vs secondary: how to tell the difference
| Primary (focal) | Secondary | |
|---|---|---|
| Where | Underarms, palms, feet, face | Often the whole body |
| Sides | Both sides, symmetrical | Can be one-sided |
| Started | Usually before age 25 | Often later in adulthood |
| At night | Stops during sleep | Night sweats are common |
| Family history | Common | Not typical |
Sweating that starts suddenly in adulthood, soaks the sheets at night, affects only one side, or comes with fever or weight loss points towards a secondary cause, which is diagnosed and managed differently from primary hyperhidrosis.
Everyday triggers that make sweating worse
Whatever the cause, certain triggers turn the volume up further. The American Academy of Dermatology and Cleveland Clinic point to:
- Stressful moments: meetings, dates, presentations, handshakes
- Caffeine: a direct nervous system stimulant
- Spicy food: capsaicin activates the same receptors as real heat
- Alcohol: widens blood vessels and raises heart rate
- Heavy, salty or ultra-processed meals
- Nicotine: can overstimulate the sweat glands
- Tight synthetic clothing that traps heat
Keeping a short sweat journal for two weeks is the easiest way to find your own triggers. Our guide on how to stop sweating so much covers 12 practical habits.
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Why the cause matters for what you do next
If hyperhidrosis starts in the nervous system, products that only work on the skin can only ever do half the job. Antiperspirants block sweat ducts where you apply them, but they can't reach the signal itself or the stress that amplifies it. That's why so many people feel dry for an hour and then soaked again.
A more complete approach works on both sides of the loop:
- The sweat itself: sage has a long tradition in Europe for excessive sweating and is recognised by the European Medicines Agency as a traditional herbal remedy for excessive sweating.
- The stress hormone: in a 2019 placebo-controlled trial, ashwagandha root extract lowered anxiety and morning cortisol.
- The calm-down signal: passion flower is a traditional calming herb studied for anxiety.
- Daily habits: bedtime antiperspirant on dry skin, fewer triggers and slow breathing before stressful moments.
Voora was built around exactly this idea. It combines four pure plant extracts at full doses, sage, ashwagandha, pine bark and passion flower, so the sweat and the stress behind it are supported every day. Read more in Supplements for excessive sweating: what the science says.
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Frequently asked questions
What is the main cause of hyperhidrosis?
In most people, an overactive sympathetic nervous system that sends too many "sweat" signals to normal sweat glands. More than 90% of cases are primary hyperhidrosis with no underlying disease.
Is hyperhidrosis genetic?
Often, yes. Up to two-thirds of people with primary hyperhidrosis have a family member with it, and a 2026 Johns Hopkins study identified a gene variant that amplifies the nerve signals behind sweating.
Can stress cause hyperhidrosis?
Stress doesn't create primary hyperhidrosis by itself, but it strongly amplifies it. Stress activates the same nervous system that controls sweating, and worrying about sweat creates more of it.
Why do I sweat so much for no reason?
If it started young, happens in specific areas on both sides and stops at night, it's most likely primary hyperhidrosis. If it began suddenly as an adult, covers the whole body or happens at night, a secondary cause such as hormones, thyroid or a medication is more likely.
What is the difference between focal and generalised hyperhidrosis?
Focal hyperhidrosis affects specific areas like the underarms, palms, feet or face, and is usually primary. Generalised hyperhidrosis affects the whole body and is more often secondary to another condition or medication.
Sources
- American Family Physician: Review of hyperhidrosis diagnosis and management, 2018
- Johns Hopkins Medicine: Excessive sweating may start in nervous system, 2026
- International Hyperhidrosis Society: Prevalence of hyperhidrosis in the US
- International Hyperhidrosis Society: Hyperhidrosis and mental health
- American Academy of Dermatology: Hyperhidrosis self-care
- Lopresti AL et al. Ashwagandha and stress: a randomised placebo-controlled trial, 2019
- European Medicines Agency: Community herbal monograph on sage leaf
This article is for general information only. These statements have not been evaluated by the Food and Drug Administration. Voora is not intended to diagnose, treat, cure or prevent any disease.
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