What causes hyperhidrosis?

Causes of Increased Sweating (Hyperhidrosis)

Hyperhidrosis is categorized as either primary (idiopathic, focal, and bilateral) or secondary (caused by underlying medical conditions or medications), and distinguishing between these two is essential for appropriate management. 1, 2

Primary Hyperhidrosis

Primary hyperhidrosis is excessive sweating without an identifiable underlying cause, typically affecting specific body regions bilaterally and symmetrically. 2, 3

Key Characteristics:

• Focal distribution: Most commonly affects palms, soles, axillae, and craniofacial regions 4, 2
• Bilateral and symmetric presentation 2
• Onset typically in childhood or adolescence 2
• Affects approximately 2.8% of the US population 2

Pathophysiology:

• The primary abnormality appears to be central, involving the hypothalamic sweat center that controls sweating in specific regions 5
• Eccrine glands are innervated by cholinergic fibers from the sympathetic nervous system, and overactivity of this system drives excessive sweating 6, 5

Secondary Hyperhidrosis

Secondary hyperhidrosis results from identifiable underlying medical conditions or medications and may be focal or generalized. 4, 2

Systematic Evaluation Using "SCREeN" Approach:

The American Academy of Dermatology recommends screening for the following categories 1:

S - Sleep Disorders

• Sleep apnea and other sleep-related conditions can trigger excessive sweating 1

C - Cardiovascular Conditions

• Hyperthyroidism (Graves disease) causes increased metabolic rate, heat production, and compensatory sweating 7
• Heart failure and other cardiovascular diseases may present with diaphoresis 7

R - Renal Disease

• Chronic kidney disease can cause uremic sweating 1

E - Endocrine Disorders

• Hyperthyroidism is a major cause, with juvenile hyperthyroidism specifically noted as decreasing exercise-heat tolerance 7
• Diabetes mellitus (particularly type 2) affects thermoregulation 7
• Diabetes insipidus impairs fluid balance and thermoregulation 7
• Hypoglycemia 1
• Pheochromocytoma 1
• Carcinoid syndrome 1

N - Neurological Conditions

• Autonomic dysfunction 1
• Parkinson's disease 1
• Stroke 1

Additional Secondary Causes:

Medications:

• Anticholinergic drugs affect thermoregulation 7
• Dopamine-reuptake inhibitors (used for ADHD) can impair sweating regulation 7
• Diuretics affect hydration status 7
• Oral retinoids (noted in dermatological conditions) 7

Infectious/Inflammatory:

• Fever from any cause increases sweating 7
• Recent illness, particularly with gastrointestinal symptoms (vomiting, diarrhea), affects hydration and thermoregulation 7

Other Medical Conditions:

• Obesity increases sweating through mechanical friction at flexural sites, sweat retention, and increased pro-inflammatory cytokines 7
• Cystic fibrosis impairs thermoregulation 7
• Malignancies (lymphoma, leukemia) 1
• Menopause 1

Dermatological Conditions:

• Congenital ichthyoses can cause hypohidrosis (reduced sweating) due to hyperkeratotic plugging of sweat ducts, though this represents impaired rather than increased sweating 7
• Hidradenitis suppurativa involves follicular occlusion and may affect sweat gland function, with obesity contributing through increased sweat retention 7

Special Consideration - Social Anxiety Disorder:

Hyperhidrosis is recognized as a manifestation of social anxiety disorder, where excessive sweating occurs in response to anxiety-provoking social situations 7

Recommended Diagnostic Workup

For patients presenting with hyperhidrosis, the following laboratory evaluation should be performed to identify secondary causes 1:

• Complete blood count 1
• Comprehensive metabolic panel 1
• Thyroid function tests (TSH, free T4) 1
• Hemoglobin A1c 1
• Serum calcium levels 1
• Vitamin D level 1
• Iron studies 1

Clinical Pitfalls

A critical pitfall is assuming all hyperhidrosis is primary without systematically excluding secondary causes, particularly thyroid dysfunction and diabetes, which are readily treatable. 1

Another common error is overlooking medication-induced hyperhidrosis—always review the patient's medication list for anticholinergics, stimulants, and other agents affecting thermoregulation. 7

In young patients with exercise-related sweating concerns, consider that recent illness with fever or gastrointestinal symptoms significantly impairs thermoregulation even after apparent recovery. 7