Sweating is regulated by the sympathetic nervous system, which signals the body's roughly 2 to 4 million eccrine sweat glands to release fluid that cools the skin. In primary focal hyperhidrosis, those nerve signals fire excessively, even when the body does not need cooling. Research summarized by the National Institutes of Health identifies a strong genetic component, with up to two-thirds of patients reporting a family history.
Secondary hyperhidrosis is different. It happens when sweating is triggered by another underlying condition such as thyroid imbalance, hormonal changes, certain medications, infections, or metabolic disorders. If your sweating started suddenly in adulthood, occurs at night, or affects your entire body, your primary care physician should evaluate you first to rule out an underlying medical cause.
Stress and anxiety amplify both forms by activating the sympathetic nervous system further. The result is a feedback loop: you sweat, you worry about sweating, and the worry triggers more sweating.
