When your body temperature rises, your nervous system triggers the sweat glands automatically to cool itself down. When the nervous system becomes overactive, without being triggered by a very warm environment or physical activity, the patient suffers from primary focal hyperhidrosis or abnormally excessive sweating. There is no known medical cause for primary hyperhidrosis, but it can be an inherited condition that runs in the patients’ families. Another type of excessive sweating is secondary hyperhidrosis which occurs due to several medical conditions. It causes heavy sweating all over the body, yet it is much less common than primary hyperhidrosis. Some medical conditions that can cause secondary hyperhidrosis are the following: Thyroid problems Infections Diabetes Menopause Nervous system disorders.