Causes of Excessive Sweating (Hyperhidrosis)
Excessive sweating (hyperhidrosis) is primarily caused by either primary focal hyperhidrosis or secondary hyperhidrosis due to underlying medical conditions, medications, or environmental factors. Understanding the specific cause is essential for appropriate management and treatment.
Primary Hyperhidrosis
Primary hyperhidrosis is characterized by excessive sweating that:
- Is bilateral and symmetric
- Affects focal areas (axillae, palms, soles, craniofacial region)
- Typically begins in childhood or adolescence
- Has no identifiable underlying medical cause
- Often has a family history component
Secondary Hyperhidrosis
Secondary hyperhidrosis is caused by underlying conditions or factors:
Medical Conditions
Endocrine disorders:
- Hyperthyroidism: Characterized by warm/moist skin, heat intolerance, nervousness, tremulousness, insomnia, weight loss, diarrhea, and proximal muscle weakness 1
- Pheochromocytoma: Presents with paroxysmal hypertension, headache, sweating, palpitations, and pallor 1
- Diabetes mellitus
- Hyperpituitarism
- Cushing's syndrome: Shows rapid weight gain with central distribution, proximal muscle weakness, depression, and hyperglycemia 1
Neurological disorders:
- Autonomic dysreflexia in spinal cord injuries (particularly above T6 level) 1
- Parkinson's disease
- Stroke
Other conditions:
- Congenital ichthyosis: Associated with hypohidrosis due to hyperkeratotic plugging of sweat glands 1
- Obstructive sleep apnea: Associated with resistant hypertension, snoring, fitful sleep, breathing pauses during sleep, and daytime sleepiness 1
- Infections and febrile illnesses
- Malignancies (lymphoma, myeloproliferative disorders)
Medications and Substances
- Antidepressants
- Stimulants
- Caffeine
- Alcohol
- Tobacco
- Illicit drugs (cocaine, amphetamines)
- Decongestants
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Oral contraceptives
- Herbal supplements 1
Environmental Factors
- Hot and humid climate
- Excessive physical activity
- Emotional stress and anxiety
- Spicy foods
- Inadequate hydration during exercise 1
Special Considerations
Exercise-Related Sweating
Exercise-induced sweating is a normal physiological response but can be excessive in some individuals. Key factors include:
- Dehydration risk increases with extended exercise, especially in hot environments
- Proper hydration before, during, and after exercise is essential (water should be taken for any moderate-to-vigorous exercise lasting >30 minutes) 1
- Environmental conditions significantly impact sweating rates
- Elderly persons, obese individuals, and those taking diuretics or antihypertensive medications are particularly prone to heat illness 1
Obesity
Obese individuals are at higher risk for excessive sweating due to:
- Greater insulation from adipose tissue
- Increased metabolic rate
- Higher core body temperature
- Increased effort required for physical activity 1
Diagnostic Approach
When evaluating excessive sweating, consider:
- Pattern: Focal vs. generalized
- Timing: During sleep (suggests secondary causes) vs. only when awake
- Onset: Childhood/adolescence (suggests primary) vs. adult onset (suggests secondary)
- Associated symptoms: Weight changes, palpitations, anxiety, fever
- Medication review: Check for substances that may increase sweating
Common Pitfalls in Diagnosis
- Failing to distinguish between primary and secondary hyperhidrosis
- Overlooking medications as potential causes
- Not considering endocrine disorders in patients with generalized sweating
- Attributing excessive sweating to anxiety without ruling out organic causes
- Missing the connection between obstructive sleep apnea and night sweats
For patients with suspected secondary hyperhidrosis, appropriate laboratory testing should be performed based on clinical suspicion, including thyroid function tests, blood glucose, and other relevant studies to identify underlying causes before initiating treatment for the excessive sweating itself.