Hyperhidrosis

Definition and Epidemiology

• Dermatology 2-Volume Set 5e, p. 777
• Fitzpatrick's Dermatology, Vol. 1-2

Pathophysiology

Classification

1. Primary (Focal/Essential) Hyperhidrosis

• Idiopathic, symmetric, affecting localized areas
• Main sites: palms, soles, axillae; face may also be involved
• Onset of volar hyperhidrosis often in childhood; axillary form typically at/after puberty
• Chronic, unremitting course with little variation by age or hormonal status
• Up to 60-80% have a positive family history - autosomal dominant with incomplete penetrance; a locus mapped to chromosome 14q

• Volar (palmoplantar): most common, ~50-60% of primary cases
• Axillary: second most common, ~30-50%
• Craniofacial, groin, or combined sites: less common
• Right axilla typically produces more sweat than left (60:40 ratio)

2. Secondary Hyperhidrosis

Diagnostic Criteria for Primary Hyperhidrosis

1. Focal, visible excess sweating
2. Present for at least 6 months
3. No apparent secondary cause
4. At least 2 of the following:
   • Bilateral and symmetric
   • Impairs activities of daily life
   • At least one episode per week
   • Age of onset <25 years
   • Positive family history
   • Stops during sleep

• Dermatology 2-Volume Set 5e, p. 778 (Table 39.1)

Evaluation

• Minor's starch-iodine test: Maps the surface area and severity of sweating. Iodine applied to the skin dries, then starch powder is dusted over it - areas of active sweating turn purple-black. Used before botulinum toxin treatment to guide injection placement and after treatment to identify residual focal activity.
• History to rule out secondary causes: medications, night sweats, fever, weight loss, hormonal symptoms
• HDSS (Hyperhidrosis Disease Severity Scale) for severity grading (1-4)
• Gravimetric test: quantifies sweat production in mg/min

Treatment - Stepwise Approach

Step 1 - Topical Antiperspirants

• Aluminum chloride hexahydrate (10-25% in anhydrous ethanol, e.g., Drysol) - first-line for all sites
• Applied to dry skin at night; wash off in the morning
• Works by blocking eccrine duct openings with aluminum-protein complexes
• More effective for axillary than palmoplantar hyperhidrosis
• Side effects: skin irritation (reduced by applying to completely dry skin)
• Glycopyrronium bromide (topical, e.g., Qbrexza cloth wipe): FDA-approved for axillary hyperhidrosis; a recent systematic review and meta-analysis (2024) confirmed its efficacy and safety (PMID: 39424822)
• Sofpironium (topical): newer agent; a 2025 systematic review supports its efficacy for primary hyperhidrosis (PMID: 39668771)

Step 2 - Iontophoresis

• Delivers tap water (or anticholinergic solutions) transdermally via mild electrical current
• Best for palmoplantar hyperhidrosis
• Mechanism: believed to obstruct eccrine ducts or affect ion transport
• Sessions 3-4x/week initially; maintenance 1-2x/week or as needed
• Effective in ~80% of palmoplantar cases; requires ongoing use to maintain effect
• Contraindicated: cardiac pacemakers, metal implants in treated area, pregnancy

Step 3 - Botulinum Toxin A (BoNT-A)

• FDA-approved for axillary hyperhidrosis (USA 2004, Canada 2001)
• Dose: 50-100 U onabotulinumtoxinA (Botox) per axilla; divided into intradermal injections 1.5-2 cm apart
• Onset: anhidrosis within 72 hours; peaks at 1 week
• Duration: 6-24 months (dose-dependent; up to 29 months reported with high-dose Dysport 200 U)
• Improves quality of life and reduces body odor for up to 7 months
• Side effects: minor bruising only; compensatory hyperhidrosis is not a clinically significant concern for axillary treatment (small surface area)
• onaA, aboA, and incoA show similar safety/efficacy; rimabotulinumtoxinB (Myobloc) - more painful, associated with systemic side effects (xerostomia, flu-like)

• More challenging: greater surface area, limited toxin diffusion in palmar skin
• Requires regional wrist blocks (median, ulnar, radial nerves) with lidocaine; or ice application for analgesia
• Dose: 100-150 U onaA per palm; 50-100 intradermal injection sites
• Onset peaks in 5-7 days; duration ~3-4 months
• Virtually all patients experience some temporary hand weakness (intrinsic muscles) lasting up to 2 weeks - thumb-index pinch most affected
• Touch-up guided by repeat starch-iodine test for residual focal areas

Step 4 - Systemic Anticholinergics

• Glycopyrrolate (oral), oxybutynin - reduce sweating by blocking muscarinic receptors
• Useful for generalized or craniofacial hyperhidrosis, or when focal treatments are impractical
• Side effects: xerostomia, urinary retention, blurred vision, constipation, tachycardia (limit long-term use)
• Oxybutynin has growing evidence for palmoplantar and generalized hyperhidrosis

Step 5 - Devices

• miraDry: Microwave thermolysis device targeting eccrine and apocrine glands in the axilla - produces permanent reduction; single or two-session protocol
• Laser (Nd:YAG, diode): Targeting subcutaneous eccrine glands
• Ultrasound: Investigational

Step 6 - Surgery

• Endoscopic thoracic sympathectomy (ETS): Surgical interruption of the sympathetic chain at T2-T4 levels
• Indications: severe, refractory palmar and axillary hyperhidrosis unresponsive to other treatments
• Highly effective for palmar hyperhidrosis (~95%)
• Major complication: compensatory hyperhidrosis - occurs in up to 1 in 3 patients after ETS; sweating shifts to the trunk, back, and thighs - can be more disabling than the original complaint
• Other complications: Horner's syndrome (if cervical chain involved), pneumothorax, hemothorax, gustatory sweating
• Less morbid procedures: local excision of axillary sweat glands (surgical curettage, liposuction-assisted curettage) for axillary disease

Special Types

Frey Syndrome (Auriculotemporal Nerve Syndrome)

• Pathologic gustatory sweating following parotid surgery, trauma, or disease
• Aberrant reinnervation: parasympathetic fibers for salivation misdirected to sweat glands
• Sweating on cheek/adjacent neck triggered by eating
• Treatment: topical anticholinergics (glycopyrrolate cream), BoNT-A injection

Compensatory Hyperhidrosis

• Secondary hyperhidrosis in one area compensating for anhidrosis elsewhere
• Well-known in: post-sympathectomy, longstanding miliaria, diabetic neuropathy (loss of lower limb sweating leading to trunk/facial compensatory sweating)

Granulosis Rubra Nasi

• Rare condition: hyperhidrosis of the nose tip, associated with papules and vesicles; often resolves at puberty

Key Takeaways

• Primary hyperhidrosis is diurnal, bilateral, symmetric, focal and stops during sleep - family history in up to 80%
• Secondary hyperhidrosis is generalized (or neurologically focal) and should prompt a workup for systemic cause or offending medication
• Treatment ladder: topical aluminum chloride → iontophoresis → BoNT-A → systemic anticholinergics → surgery (ETS - reserve for severe refractory cases due to compensatory hyperhidrosis risk)
• BoNT-A is FDA-approved for axillary hyperhidrosis with excellent efficacy (Level A); palmar use requires nerve blocks and carries temporary hand weakness
• ETS is definitive for palmar disease but 1/3 of patients develop troublesome compensatory hyperhidrosis

Recent evidence note (2024-2025): Topical glycopyrronium bromide (PMID: 39424822) and sofpironium (PMID: 39668771) have strong systematic review-level evidence for axillary/primary hyperhidrosis. Radiofrequency microneedling is also supported as an effective device option (PMID: 39761372).