Hyperhidrosis
On this page
Direct answer
Hyperhidrosis is sweating in excess of what thermoregulation requires, and it is classified as primary focal disease or secondary generalised sweating. Primary focal hyperhidrosis is idiopathic and symmetrical, affecting the palms, soles, axillae and face, and it usually begins in childhood or adolescence. Secondary causes such as thyroid disease, diabetes, infection, malignancy and drugs must be excluded first, and topical aluminium chloride is the usual first-line therapy for focal disease.
What you must remember
- Definition: eccrine sweating beyond the physiological need for heat control, driven by sympathetic cholinergic overactivity.
- Sweat pattern: primary focal sweating is symmetrical, stops during sleep and does not occur on the trunk; sweating during sleep points to a secondary cause.
- Sites: palms, soles, axillae and the craniofacial region in primary disease, whereas secondary sweating is usually generalised.
- Secondary causes: hyperthyroidism, diabetes mellitus, menopause, tuberculosis, lymphoma, chronic infection, and drugs such as antidepressants and opioid withdrawal.
- First line: aluminium chloride hexahydrate applied to dry skin at night and washed off in the morning; irritation is the main limitation.
- Physical measures: iontophoresis with tap water is effective for palmar and plantar disease and needs repeated sessions.
- Escalation: botulinum toxin injections work in axillary and palmar disease for several months, while endoscopic thoracic sympathectomy is reserved for refractory palmar disease.
A stepwise approach to focal sweating
A candidate whose palmar sweating disrupts writing or handshakes needs a focused history before any treatment is chosen. The sequence below follows standard dermatology teaching and moves from the least to the most invasive option.
- Exclude secondary causes: check thyroid function and blood glucose, review the drug history and look for fever, weight loss or lymphadenopathy. Generalised or nocturnal sweating should prompt a wider work-up for tuberculosis or lymphoma.
- Topical aluminium chloride: apply the hexahydrate solution to dry skin at bedtime and wash it off in the morning. Dryness and stinging are common, so many patients start on alternate nights.
- Iontophoresis: immerse the palms or soles in tap water while a weak direct current passes through, in repeated sessions, usually several a week at the start. It suits palmar and plantar disease that does not settle with topical therapy.
- Botulinum toxin: inject the axillae or palms intradermally to block acetylcholine release at the sweat glands. The effect lasts several months, so repeat injections are needed, and palmar use is off-label in many settings.
- Oral agents: anticholinergics such as oxybutynin are second-line options, limited by dry mouth and urinary symptoms.
- Surgery: endoscopic thoracic sympathectomy is reserved for severe palmar hyperhidrosis that has failed other measures. Compensatory sweating on the trunk, back or legs is common afterwards, so counselling is essential.
Where the exam tries to catch you
Hyperhidrosis questions usually test the primary and secondary distinction and the order of escalation.
- Trap: choosing sympathectomy early for palmar sweating Correct: it is reserved for refractory disease, because compensatory sweating is a frequent outcome.
- Trap: treating night sweats as primary focal disease Correct: primary focal sweating stops during sleep, so night sweats point to tuberculosis, lymphoma or another secondary cause.
- Trap: choosing an oral anticholinergic as first-line for focal sweating Correct: topical aluminium chloride is first-line, and oral agents come later.
- Trap: labelling hyperhidrosis in a thin, tremulous patient as anxiety Correct: hyperthyroidism is a classic secondary cause and must be investigated before a psychological label is accepted.
Frequently asked questions
What is the first-line treatment for primary focal hyperhidrosis?
Topical aluminium chloride hexahydrate, applied to dry skin at night, is the first-line treatment for primary focal hyperhidrosis. It is inexpensive and effective for the axillae, palms and soles when used consistently. Irritation is its main limitation.
Which investigations exclude a secondary cause of hyperhidrosis?
Thyroid function tests and blood glucose or HbA1c form the basic screen for secondary hyperhidrosis. A chest radiograph is added when tuberculosis is suspected, and lymphoma needs evaluation when night sweats, fever or weight loss are present. The choice of tests depends on the clinical pattern.
How does iontophoresis help in palmar hyperhidrosis?
Iontophoresis passes a weak direct current through tap water in which the palms or soles are immersed. Its mechanism is not fully understood, but it reduces sweat output in the treated areas. Sessions must be repeated to maintain the benefit.
When is endoscopic thoracic sympathectomy indicated for hyperhidrosis?
Endoscopic thoracic sympathectomy is reserved for severe palmar hyperhidrosis that has not responded to topical, iontophoretic and injectable treatment. Compensatory sweating on the trunk, back or legs is a recognised and sometimes troublesome outcome. Surgery is therefore a last resort, after counselling about this risk.