Key points

• Postganglionic sympathetic C fibres supply the sweat glands

• Iontophoresis involves passing a small current into the skin using tap water

• Botox injections are useful for axillary, palmar or frontal hyperhidrosis but repeat injections are required

• Thoracoscopic sympathectomy of T2 and T3 ganglion for palmar and T2 T3 and T4 ganglia for axillary hyperhidrosis is very effective

• Patients should be warned of side effects such as compensatory hyperhidrosis, Horner's syndrome, pneumothorax and haemothorax

• Local surgical treatments include curettage, skin excision or liposuction

Introduction

Hyperhidrosis is the production of excessive quantities of sweat, and is caused by hyper-function of the exocrine sweat glands, which are controlled by the sympathetic nervous system via postsynaptic cholinergic fibres.

Nerves from the hypothalamic preoptic sweat centre synapse in the intermediolateral cell columns without crossing. The myelinated preganglionic fibres pass out in the anterior roots to the sympathetic chain. Unmyelinated postganglionic C fibres arising from the sympathetic ganglia join the peripheral nerves and pass out to the sweat glands.

Sweating can be induced by thermal stimuli and emotional stress. Emotional sweating can occur over the entire skin but is more prevalent in the palms, axillae and soles. This stops during sleep when thermal sweating can continue.

A dysfunction of the central sympathetic nervous system, possibly of the hypothalamic nucleus or prefrontal areas is suspected to be the cause of hyperhidrosis.

Hyperhidrosis may be primary or secondary; localized or generalized. Secondary hyperhidrosis may be due to hyperthyroidism or phaeochromcytoma.