Excessive sweating is primarily caused by an overactive nervous system: in people with hyperhidrosis, the sweat glands receive more signals than necessary from the nerves that control sweating. Primary hyperhidrosis is often linked to genetics and typically affects specific areas like the hands, feet, underarms, or face, usually starting in adolescence or early adulthood. Secondary hyperhidrosis is caused by another condition, such as thyroid disorders, diabetes, infections, or hormonal changes, or is a side effect of certain medications. Triggers like stress, anxiety, spicy foods, or heat can make sweating worse in both types.