Causes of Hyperhidrosis

The Root Cause: An Overactive Sympathetic Nervous System

While the precise trigger is not fully understood, doctors have successfully linked hyperhidrosis to overactivity in the sympathetic nervous system — specifically a structure called the Thoracic Sympathetic Ganglion Chain, which runs along the vertebrae of the spine inside the chest cavity. This chain acts as the control center for the body’s sweat response.

In patients with hyperhidrosis, this chain misfires — sending constant sweat signals even when the body has no physiological need to cool down. The result is sweating that is unpredictable, uncontrollable, and far beyond what any situation demands.

The Role of Genetics

The most widely accepted theory is that hyperhidrosis is genetic. Studies consistently show that 62–65% of patients have at least one close family member with the same condition — a pattern consistent with an autosomal dominant inheritance with reduced penetrance. This means the gene does not need to be inherited from both parents to express, but having two copies increases the likelihood and severity of symptoms.

Symptoms typically emerge in childhood or early adolescence and persist throughout life without treatment. They do not resolve on their own in severe cases.

The Sweat Glands Involved

The sympathetic chain controls two types of glands responsible for perspiration throughout the body:

• Eccrine glands — the primary culprit in hyperhidrosis. Concentrated most densely in the palms of the hands and soles of the feet, these glands produce a watery, odourless sweat directly onto the skin surface. Their overactivity causes the wet, dripping hands and feet most patients describe.
• Apocrine glands — located in the groin, armpit, and facial regions. These secrete a thicker, oilier substance and are partly responsible for body odour. They are less directly affected by sympathectomy than the eccrine glands.

The eccrine glands in the hands and feet are the most commonly affected. To a lesser degree, the face and armpits are involved. Another expression of hyperactive sympathetic activity is facial blushing — an involuntary reddening of the face triggered by the same overactive nerve chain.

Primary vs. Secondary Hyperhidrosis

Not all excessive sweating is primary hyperhidrosis. Secondary hyperhidrosis — sweating caused by an underlying medical condition — must be ruled out before treatment can begin. Common secondary causes include:

• Hyperthyroidism — an overactive thyroid elevates metabolic rate and triggers widespread sweating
• Menopause — hormonal shifts cause hot flashes and night sweats, often lasting 7–11 years
• Psychiatric disorders — severe anxiety can produce situational sweating, though it is not the root cause of primary hyperhidrosis
• Obesity — increased metabolic demand raises core body temperature
• Certain medications — antidepressants, opioids, and hormonal therapies are common culprits
• Systemic illness — infections, diabetes, lymphoma, and neurological conditions can all produce excessive sweating

Dr. Basseri conducts a thorough differential diagnosis — reviewing medical history, family background, and physical examination — to confirm that a patient has primary hyperhidrosis before any surgical recommendation is made.

Why Treating the Cause Works So Well

Because the root cause of primary hyperhidrosis is a specific, identifiable nerve chain in the chest, surgical treatment can target it with extraordinary precision. Endoscopic Thoracic Sympathectomy (ETS) interrupts the misfiring signals at their source — and the results are immediate and permanent in the vast majority of patients.

This mechanistic clarity is why our success rate stands at 99.2% across more than 9,400 treated patients. The cause is known. The solution is surgical. The results speak for themselves.