this scheme, excessive sweating in an area of 100 square centimeters (16 square inches) or more is differentiated from sweating that affects only a small area. Another classification scheme is based on possible causes of hyperhidrosis. Causes The cause of primary hyperhidrosis is unknown. Anxiety or excitement can exacerbate the condition. A common complaint of patients is they get nervous because they sweat, then sweat more because they are nervous. Other factors can play a role, including certain foods and drinks, nicotine, caffeine, and smells. Similarly, secondary (generalized) hyperhidrosis has many causes including certain types of cancer, disturbances of the endocrine system, infections, and medications. Primary Primary (focal) hyperhidrosis has many causes. Idiopathic unilateral circumscribed hyperhidrosis Reported association with: Blue rubber bleb nevus Glomus tumor POEMS syndrome Burning feet syndrome (Gopalan's) Trench foot Causalgia Pachydermoperiostosis Pretibial myxedema Gustatory sweating associated with: Encephalitis Syringomyelia Diabetic neuropathies Herpes zoster (shingles) Parotitis Parotid abscesses Thoracic sympathectomy Auriculotemporal or Frey's syndrome Miscellaneous Lacrimal sweating (due to postganglionic sympathetic deficit, often seen in Raeder's syndrome) Harlequin syndrome Emotional hyperhidrosis Cancer A variety of cancers have been associated with the development of secondary hyperhidrosis including lymphoma, pheochromocytoma, carcinoid tumors (resulting in carcinoid syndrome), and tumors within the thoracic cavity. Endocrine Certain endocrine conditions are also known to cause secondary hyperhidrosis including diabetes mellitus (especially when blood sugars are low), acromegaly, hyperpituitarism, pheochromocytoma (tumor of the adrenal glands, present in 71% of patients) and various forms of thyroid disease. Medications Use of selective serotonin reuptake inhibitors (e.g., sertraline) is a common cause of medication-induced secondary hyperhidrosis. Other medications associated with secondary hyperhidrosis include tricyclic antidepressants, stimulants, opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), glyburide, insulin, anxiolytic agents, adrenergic agonists, and cholinergic agonists. Miscellaneous In people with a history of spinal cord injuries Autonomic dysreflexia Orthostatic hypotension Posttraumatic syringomyelia Associated with peripheral neuropathies Familial dysautonomia (Riley-Day syndrome) Congenital autonomic dysfunction with universal pain loss Exposure to cold, notably associated with cold-induced sweating syndrome Associated with probable brain lesions Episodic with hypothermia (Hines and Bannick syndrome) Episodic without hypothermia Olfactory Associated with systemic medical problems Parkinson's disease Fibromyalgia Congestive heart failure Anxiety Obesity Menopausal state Night sweats Compensatory Infantile acrodynia induced by chronic low-dose mercury exposure, leading to elevated catecholamine accumulation and resulting in a clinical picture resembling pheochromocytoma. Febrile diseases Vigorous exercise A hot, humid environment Diagnosis Symmetry of excessive sweating in hyperhidrosis is most consistent with primary hyperhidrosis. To