Hyperhidrosis — Viva

Q1: Definition and classification (2 min)

Examiner: Define hyperhidrosis and classify it. How do primary focal and secondary generalised hyperhidrosis differ?

Candidate answer: Hyperhidrosis is sweating beyond the amount required for thermoregulation. The two main categories are primary focal hyperhidrosis, which is idiopathic, bilateral, symmetric, focal to palms/soles/axillae/face, onset in childhood or adolescence, ceases during sleep and often familial; and secondary generalised hyperhidrosis, which is due to an underlying cause such as endocrine disease, neurological disease, malignancy, infection or drugs, often begins later in life, may be generalised or nocturnal, and is associated with systemic symptoms.

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Q2: Pathophysiology (2 min)

Examiner: Which neurotransmitter and receptor mediate eccrine sweating, and why does this matter for treatment?

Candidate answer: Eccrine sweat glands are innervated by sympathetic post-ganglionic fibres that are cholinergic: they release acetylcholine, which acts on muscarinic-3 (M3) receptors on the secretory coil of the eccrine gland. This explains why anticholinergic drugs block M3 receptors, botulinum toxin blocks acetylcholine release, and sympathectomy interrupts the sympathetic drive. It is a common exam trap that the fibres are sympathetic yet cholinergic, not adrenergic.

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Q3: Clinical assessment (2 min)

Examiner: How would you assess the severity of hyperhidrosis at the bedside?

Candidate answer: I would use the Hyperhidrosis Disease Severity Scale (HDSS), a four-point patient-reported scale where 1 is never noticeable and 4 is intolerable and always interfering. A score of 3 or 4 indicates severe disease. I would also perform the starch-iodine (Minor) test: paint iodine on the skin, dust with starch, and look for a blue-black colour where sweat is present. This maps the affected area and can be used before botulinum toxin injections or to monitor response.

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Q4: Management by site (3 min)

Examiner: A patient has severe palmar and axillary hyperhidrosis. Outline your stepwise management.

Candidate answer: For axillary disease, first-line is topical aluminium chloride 20% applied at night to dry skin and washed off in the morning. If this fails, I would use botulinum toxin A 50–100 units per axilla intradermally, which lasts 4–9 months. A durable third-line option is microwave thermolysis (miraDry). For palmar disease, first-line is tap-water iontophoresis at 15–20 mA for 20–30 minutes, 3–4 times per week initially. If that fails, I would try topical aluminium chloride or botulinum toxin 100–200 units per palm, usually under nerve block because it is painful. Endoscopic thoracic sympathectomy (ETS) is a last resort for severe refractory palmar disease because of the risk of compensatory hyperhidrosis in 50–90% of patients.

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Q5: Secondary causes and red flags (3 min)

Examiner: A 55-year-old man presents with new-onset generalised sweating and night sweats. What would you investigate, and why?

Candidate answer: New-onset generalised sweating with night sweats is secondary hyperhidrosis until proven otherwise. The most concerning causes are lymphoma or leukaemia (B symptoms: fever, night sweats, weight loss), tuberculosis, HIV, endocarditis, hyperthyroidism and phaeochromocytoma. I would arrange a full blood count, ESR/CRP, LDH, fasting glucose, HbA1c, thyroid function tests, chest X-ray, HIV test and blood cultures. If there were hypertension, palpitations or episodic anxiety, I would check 24-hour urinary or plasma metanephrines for phaeochromocytoma. CT imaging and specialist referral would follow if initial tests were abnormal.

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Q6: Complications and counselling (2 min)

Examiner: What are the most important adverse effects of oral anticholinergics and ETS?

Candidate answer: Oral anticholinergics cause dry mouth, blurred vision, constipation, urinary retention, tachycardia, heat intolerance and confusion (especially oxybutynin). They are contraindicated in narrow-angle glaucoma, urinary retention, paralytic ileus and severe cardiac disease. ETS carries a high risk of compensatory hyperhidrosis on the trunk, which is frequent and can be severe and irreversible; other risks include Horner syndrome, pneumothorax, intercostal neuralgia and gustatory sweating. This is why ETS is only considered after all other treatments have failed and only for severe palmar disease.^[1][5]

References5ShowHide

1. [1]Delgado LM, D'Ambrosio PD, da Nobrega Oliveira REN, et al. T2-sparing vs T2-including sympathectomy for hyperhidrosis: a meta-analysis on compensatory sweating J Cardiothorac Surg, 2026.PMID 42351253
2. [2]Lowe NJ, Glaser DA, Eadie N, et al. Botulinum toxin type A in the treatment of primary axillary hyperhidrosis: a 52-week multicenter double-blind, randomized, placebo-controlled study of efficacy and safety J Am Acad Dermatol, 2007.PMID 17306417
3. [3]Lowe NJ, Glaser DA, Eadie N, et al. Botulinum toxin type A in the treatment of primary axillary hyperhidrosis: a 52-week multicenter double-blind, randomized, placebo-controlled study of efficacy and safety J Am Acad Dermatol, 2007.PMID 17306417
4. [4]Kim J, Han N, Koo H, et al. Efficacy and Safety of Topical Anticholinergics in the Treatment of Primary Axillary Hyperhidrosis: A Systematic Review and Meta-analysis Clin Drug Investig, 2026.PMID 41989535
5. [5]Pariser DM, Krishnaraja J, Tremblay TM, et al. Randomized, placebo- and active-controlled crossover study of the safety and efficacy of THVD-102, a fixed-dose combination of oxybutynin and pilocarpine, in subjects with primary focal hyperhidrosis J Drugs Dermatol, 2017.PMID 28300854