What causes excessive sweating (hyperhidrosis)?

Causes of Excessive Sweating (Hyperhidrosis)

Excessive sweating (hyperhidrosis) is primarily caused by either primary (focal) hyperhidrosis, which is idiopathic, or secondary hyperhidrosis, which results from underlying medical conditions, medications, or environmental factors. 1

Primary vs. Secondary Hyperhidrosis

Primary Hyperhidrosis

• Bilaterally symmetric and focal
• Typically affects specific areas:
  • Axillae (armpits)
  • Palms of hands
  • Soles of feet
  • Craniofacial region
• Usually begins in childhood or adolescence
• Often has a family history component
• No underlying medical cause identified

Secondary Hyperhidrosis

• May be focal or generalized
• Caused by identifiable underlying conditions or factors

Common Causes of Secondary Hyperhidrosis

Endocrine Disorders

• Hyperthyroidism: Characterized by tachycardia, tremors, nervousness, and heat intolerance 1
• Hyperpituitarism/Growth hormone excess: Particularly in children with abnormal growth patterns 1
• Diabetes mellitus: Can cause autonomic neuropathy with hyperhidrosis affecting face and upper body 1
• Hyperparathyroidism: Associated with hypercalcemia 2

Neurological Conditions

• Autonomic dysreflexia: Particularly in spinal cord injuries above T6 level 1
• Parkinson's disease: Can cause excessive sweating as part of autonomic dysfunction 3
• Congenital ichthyosis: Associated with hypohidrosis from plugging of sweat ducts by hyperkeratosis 2

Psychological Factors

• Social anxiety disorder: Often presents with hyperhidrosis in social situations 1

Medications and Substances

• Stimulants: Can contribute to hyperhidrosis 1
• Antidepressants: Particularly serotonergic medications 1
• Other medications: Loop diuretics, ACE inhibitors, proton-pump inhibitors 1

Environmental Factors

• Extreme heat exposure: Can exacerbate hyperhidrosis symptoms 1
• Hot and humid weather: Increases risk of excessive sweating 2
• Physical exertion: Especially with insufficient rest/recovery time 2

Other Medical Conditions

• Infections: Particularly those causing fever
• Obesity: BMI ≥ 85th percentile increases risk of heat-related sweating 2
• Recent illness: Especially those involving gastrointestinal distress or fever 2

Diagnostic Considerations

When evaluating excessive sweating, consider:

1. Age of onset: New-onset hyperhidrosis in adulthood should raise suspicion for underlying medical conditions 1
2. Pattern of sweating: Focal vs. generalized
3. Thyroid function tests: Should be considered in all patients with hyperhidrosis 1
4. Severity assessment: Using the Hyperhidrosis Disease Severity Scale (HDSS) 1

Important Clinical Pearls

• Always rule out secondary causes before diagnosing primary hyperhidrosis
• Hyperthyroidism is one of the most common endocrine causes of excessive sweating 2
• Medications are a frequently overlooked cause of hyperhidrosis
• Environmental factors and physical activity can significantly exacerbate sweating in predisposed individuals 2
• Congenital ichthyosis can paradoxically cause hypohidrosis (reduced sweating) due to plugging of sweat ducts, leading to heat intolerance 2

Understanding the specific cause of hyperhidrosis is crucial for determining appropriate treatment, which may include topical treatments, oral medications, botulinum toxin injections, or addressing the underlying condition in cases of secondary hyperhidrosis.