What causes hyperhidrosis?

Causes of Hyperhidrosis

Hyperhidrosis is caused by either primary (idiopathic) sympathetic overactivity or secondary conditions including endocrine disorders (especially hyperthyroidism and diabetes), cardiovascular disease, medications, infections, malignancies, and neurological disorders. 1, 2

Primary vs. Secondary Hyperhidrosis: The Critical Distinction

The first step is determining whether hyperhidrosis is primary or secondary, as this fundamentally changes management:

• Primary hyperhidrosis never occurs during sleep - this is the key distinguishing feature 2
• Primary hyperhidrosis is bilaterally symmetric, focal (affecting palms, soles, axillae, or craniofacial regions), begins in childhood/adolescence, and has no identifiable underlying cause 3, 4
• Secondary hyperhidrosis may be focal or generalized, can occur during sleep, and results from an underlying medical condition or medication 3, 5

Secondary Hyperhidrosis: The "SCREeN" Approach

Use the systematic "SCREeN" approach to identify secondary causes: 1, 2

S - Sleep Disorders

• Sleep apnea triggers excessive nocturnal sweating 1
• Overnight oximetry or polysomnography should be considered when sleep disorders are suspected 2

C - Cardiovascular Conditions

• Heart failure presents with diaphoresis from sympathetic activation 1, 2
• ECG and BNP testing when clinically indicated 2

R - Renal Disease

• Chronic kidney disease causes uremic sweating 1

E - Endocrine Disorders

• Hyperthyroidism (Graves disease) is a major cause, increasing metabolic rate and heat production 1, 2
• Diabetes mellitus (particularly type 2) affects thermoregulation 1
• Hypoglycemia triggers acute sweating episodes 1
• Pheochromocytoma causes episodic sweating with hypertension 1
• Carcinoid syndrome produces flushing and sweating 1

N - Neurological Conditions

• Autonomic dysfunction disrupts normal sweating regulation 1
• Parkinson's disease causes hyperhidrosis in up to 50% of patients 1
• Stroke can produce focal or generalized sweating 1

Additional Secondary Causes

Medications (Common Pitfall)

• Anticholinergic drugs paradoxically affect thermoregulation 1
• Dopamine-reuptake inhibitors (ADHD medications) impair sweating regulation 1
• Diuretics affect hydration status 1
• Oral retinoids cause hyperhidrosis 1
• A comprehensive medication review is mandatory as this is frequently overlooked 2

Malignancies

• Lymphoma and leukemia cause night sweats 1
• Unexplained night sweats require thorough malignancy evaluation 2

Hormonal Factors

• Menopause produces vasomotor symptoms with sweating 1

Infectious Causes

• Fever from any infection increases compensatory sweating 1
• Recent illness with gastrointestinal symptoms (vomiting, diarrhea) impairs thermoregulation even after apparent recovery 1

Obesity

• Increases sweating through mechanical friction at flexural sites, sweat retention, and increased pro-inflammatory cytokines 1

Mandatory Laboratory Workup for Secondary Causes

The American Academy of Dermatology recommends the following laboratory evaluation: 1, 2

• Complete blood count 1, 2
• Comprehensive metabolic panel 1, 2
• Thyroid function tests (TSH, free T4) - hyperthyroidism is a major treatable cause 1, 2
• Hemoglobin A1c - diabetes screening 1, 2
• Serum calcium levels - hyperparathyroidism evaluation 1, 2
• Vitamin D level 1
• Iron studies 1

Additional testing based on clinical suspicion may include morning urine osmolality, PTH, and overnight oximetry 2

Critical Clinical Pitfalls to Avoid

Pitfall #1: Assuming Primary Hyperhidrosis Without Systematic Exclusion

• The most critical error is failing to systematically exclude secondary causes, particularly thyroid dysfunction and diabetes, which are readily treatable 1
• Always complete the "SCREeN" evaluation and laboratory workup before diagnosing primary hyperhidrosis 1, 2

Pitfall #2: Overlooking Medication-Induced Hyperhidrosis

• Review the complete medication list for anticholinergics, stimulants, antihypertensives, psychiatric medications, and hormonal therapies 1, 2
• This is a common, reversible cause that is frequently missed 1

Pitfall #3: Ignoring Recent Illness in Young Patients

• In young patients with exercise-related sweating concerns, recent illness with fever or gastrointestinal symptoms significantly impairs thermoregulation even after apparent recovery 1
• Consider this temporal relationship before extensive workup 1

Pitfall #4: Missing Nocturnal Sweating Significance

• If sweating occurs during sleep, it is NOT primary hyperhidrosis 2
• Nocturnal sweating mandates evaluation for sleep apnea, malignancy, infections, and endocrine disorders 1, 2