What are the causes of hyperhidrosis?

Causes of Hyperhidrosis

Hyperhidrosis is classified as either primary (idiopathic) or secondary, with primary hyperhidrosis accounting for 93% of all cases and being bilaterally symmetric focal sweating without an underlying cause, while secondary hyperhidrosis results from identifiable medical conditions, medications, or systemic disorders. 1

Primary Hyperhidrosis

Primary hyperhidrosis is idiopathic and believed to result from sympathetic nervous system overactivity affecting eccrine sweat glands innervated by cholinergic fibers. 2, 1

• The condition typically affects specific body regions bilaterally and symmetrically, most commonly the axillae, palms, soles, and craniofacial areas 3, 1
• Primary hyperhidrosis does not occur during sleep, which is a key distinguishing feature from secondary causes 4
• The exact pathophysiology remains unclear, but sympathetic overactivity is the leading hypothesis 1

Secondary Hyperhidrosis

Secondary hyperhidrosis may be focal or generalized and requires systematic evaluation for underlying causes using the "SCREeN" approach: Sleep disorders, Cardiovascular conditions, Renal disease, Endocrine disorders, and Neurological conditions. 5, 4

Endocrine and Metabolic Causes

• Hyperthyroidism is a major cause, with thyroid dysfunction directly affecting thermoregulation and sweating patterns 6, 4
• Diabetes mellitus and metabolic disturbances including pheochromocytoma can trigger excessive sweating 7, 3
• Endocrine abnormalities should be evaluated with thyroid function tests, hemoglobin A1c, and serum calcium levels 5, 4

Cardiovascular Causes

• Heart failure can present with sweating as part of sympathetic activation 6
• Cardiovascular evaluation should include ECG and BNP when clinically indicated 4

Infectious Causes

• Tuberculosis is a classic infectious cause of generalized hyperhidrosis 7
• Other systemic infections can trigger sweating through inflammatory mediators 6

Neurological Causes

• Neurological disorders affecting autonomic function can cause both generalized and focal sweating 7, 3
• Frey's syndrome is a specific form of secondary focal hyperhidrosis occurring after parotid gland surgery or injury, characterized by sweating and flushing during eating 7

Medication-Induced Causes

• A comprehensive medication review is mandatory, as numerous drugs can cause secondary hyperhidrosis 4, 3
• Common culprits include certain antihypertensives, psychiatric medications, and hormonal therapies 4

Malignancy

• Unexplained night sweats should raise suspicion for underlying malignancy and require thorough evaluation 4
• Lymphomas and other hematologic malignancies commonly present with nocturnal sweating 4

Sleep Disorders

• Sleep apnea and other sleep disturbances can cause nocturnal hyperhidrosis 5, 4
• Overnight oximetry or polysomnography should be considered when sleep disorders are suspected 4

Key Diagnostic Distinctions

Nocturnal sweating is almost always indicative of secondary hyperhidrosis and mandates evaluation for serious underlying conditions. 4 Primary hyperhidrosis characteristically does not occur during sleep, making this a critical distinguishing feature 4, 3.

The distribution pattern is diagnostically important: bilateral symmetric focal sweating suggests primary hyperhidrosis, while generalized or asymmetric sweating points toward secondary causes. 7, 3

Essential Workup for Secondary Causes

When secondary hyperhidrosis is suspected, obtain: 5, 4

• Complete blood count and comprehensive metabolic panel
• Thyroid function tests
• Hemoglobin A1c
• Iron studies, vitamin D, and zinc levels
• Serum calcium
• Additional testing based on clinical suspicion (morning urine osmolality, PTH, overnight oximetry)