Hyperhidrosis is a condition characterized by abnormally increased sweating, in excess of that required for regulation of body temperature. Although primarily a benign physical burden, hyperhidrosis can deteriorate quality of life from a psychological, emotional, and social perspective. This excess of sweat happens even if the person is not engaging in tasks that require muscular effort, and it does not depend on the exposure to heat. Common places to sweat can include underarms, face, neck, back, groin, feet, and hands. It has been called by some researchers the silent handicap.Both diaphoresis and hidrosis can mean either perspiration (in which sense they are synonymous with sweating) or excessive perspiration, in which case they refer to a specific, narrowly defined, clinical disorder. Classification
Hyperhidrosis can either be generalized, or localized to specific parts of the body. Hands, feet, armpits, groin, and the facial area are among the most active regions of perspiration due to the high number of sweat glands (eccrine glands in particular) in these areas. When excessive sweating is localized (e.g. palms, soles, face, underarms, scalp) it is referred to as primary hyperhidrosis or focal hyperhidrosis. Excessive sweating involving the whole body is termed generalized hyperhidrosis or secondary hyperhidrosis. It is usually the result of some other, underlying condition.
Idiopathic unilateral circumscribed hyperhidrosis
Reported association with:
Blue rubber bleb nevus
Glomus tumor
POEMS syndrome
Burning feet syndrome (Gopalans)
Trench foot
Causalgia
Pachydermoperiostosis
Pretibial myxedema
Gustatory sweating associated with:
Encephalitis
Syringomyelia
Diabetic neuropathies
Herpes zoster (shingles)
Parotitis
Parotid abscesses
Thoracic sympathectomy
Auriculotemporal or Freys syndrome
Miscellaneous
Lacrimal sweating (due to postganglionic sympathetic deficit, often seen in Raeders 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
Parkinsons 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 diagnose this condition, a dermatologist gives the patient a physical exam.