Excessive sweating is often brought to the attention of the physician when it becomes socially unacceptable, the underlying cause ranging from trivial to serious. Apart from heat stroke, the causes of deficient sweating are rare and usually arise from congenital disorders of the sweat glands, such as hypohidrotic ectodermal dysplasia, a condition associated with poor hair and teeth formation. Absent sweating can also be caused by miliaria, which is caused by plugging or rupture of the sweat ducts. Excessive sweating is commonly encountered as it is a physiological accompaniment to pain, nausea, vomiting (p. 494) and shock (p. 421). The causes in the absence of these symptoms have been listed above. Excessive sweating may be episodic or constant. Episodic bouts of sweating may be due to hypogylcaemia, phaeochromocytoma, carcinoid syndrome or menopause. Patients with hypogylcaemia often complain of associated tremor, dizziness, anxiety and hunger. Paroxysmal release of catecholamines by phaeochromocytomas may produce attacks of sweating, hypertension, palpitations, headaches and anxiety. It usually comes to medical attention presenting as a result of hypertension. Carcinoid syndrome is produced by a variety of hormones secreted by enterochromaffin tumours, originating from the small bowel in the presence of hepatic metastases. Episodic sweating is associated with brick-red flushing, diarrhoea, wheezing and occasionally right-sided heart lesions. Hot flushes and sweating may also be prominent symptoms experienced by women reaching the menopause; the aetiology has often been attributed to alterations in the concentrations of female reproductive hormones. Patients with night sweats may complain of waking up with their clothes and bed sheets drenched in perspiration. Classically, these features are reported with TB and Hodgkin’s disease. The accompanying symptoms of pulmonary TB include weight loss, cough and haemoptysis. With Hodgkin’s disease, patients may complain of localised lymphadenopathy, weight loss, pruritus, fever and malaise. Constant sweating and heat intolerance are features of thyrotoxicosis. This may result from increased metabolic rate and may be accompanied by symptoms of increased appetite with weight loss, emotional lability, diarrhoea and palpitations. Rarely, excessive sweating may result from tumours encroaching on the hypothalamus. Enquiries should be undertaken regarding substance dependency, as withdrawal states can produce severe sweating and hallucinations.
Sweating Abnormalities
History
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