Excessive Sweating

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

  • Drugs: Alcohol, Tricyclic Antidepressants, Pilocarpine
  • Alcohol and Drug Withdrawal
  • Shock/Syncope
  • Intense Pain
  • Hyperhidrosis
  • Other Infections (e.g. TB, HIV, Endocarditis, Brucellosis, Lyme Disease)

Rare Diagnoses

  • Dumping Syndrome (post gastric surgery)
  • Malignancy (e.g. Lymphoma)
  • Organic Nerve Lesions: Brain Tumours, Spinal Cord Injury (Sweating is Localised to Dermatome Involved)
  • Pachydermoperiostosis: Localised to Skin Folds of Forehead and Extremities
  • Hyperpituitarism/Acromegaly
  • Rare Vasoactive Tumours: Phaeochromocytoma, Carcinoid
  • Connective Tissue Disorders

Ready Reckoner

Key distinguishing features of the most common diagnoses

MenopauseAnxietyInfectionLow GlucoseHyperthyroid
Short HistoryNoNoYesYesNo
Vasoconstricted SkinNoPossiblePossibleYesPossible
Raised Body TemperatureNoNoYesNoNo
Systemically UnwellNoNoYesYesYes

Possible Investigations


Possible:FSH/LH, LFT, glucose.

Small Print:Autoimmune screen, CXR, tests for uncommon infections, 24 h urinary 5-HIAA, 24 h urinary-free catecholamines and VMAs, CT/MRI scan.

  • FBC/ESR/CRP: ESR/CRP and WCC raised in infection. Raised ESR/CRP and anaemia possible in lymphoma and other malignancies.
  • TFTs: May reveal thyrotoxicosis as a cause of chronic sweating.
  • Glucose: In reactive hypoglycaemia only useful at the time of the sweating.
  • FSH/LH: Helps if diagnosis of menopause in doubt.
  • LFT: May reveal high alcohol intake.
  • CXR might reveal occult infection (especially TB) or malignancy.
  • Tests for uncommon infections (e.g. blood test for HIV or Lyme disease, echocardiography for endocarditis).
  • Autoimmune screen: May help in confirming diagnosis of connective tissue disease.
  • 24 h urinary 5-HIAA: If carcinoid syndrome suspected.
  • 24 h urinary-free catecholamines and VMAs: If phaeochromocytoma suspected.

Top Tips

  • Length of history is very helpful – short-term sweating is likely to have an apparent, acute cause; if long-term, the diagnosis is more likely to be constitutional or anxiety; in the medium term, the differential diagnosis is much wider.
  • Anxiety rarely causes night sweats.
  • Do not underestimate the potentially devastating effect of hyperhidrosis.

Red Flags

  • Lack of fever does not exclude infection. In some infections (e.g. TB, brucellosis) – and lymphoma – sweating can be out of phase with fever.
  • If the problem is persistent, a full examination is advisable, paying attention to the lymph nodes, liver and spleen. If no cause is apparent, have a low threshold for investigations or referral, particularly if the patient is unwell or losing weight.
  • Consider unusual infections in the recently returned traveller (e.g. TB, typhoid).
  • Episodic skin flushing (especially provoked by alcohol) with diarrhoea and breathlessness is likely to be caused by anxiety – but don’t forget carcinoid syndrome as a rare possibility.

Published: 2nd August 2022 Updated: 10th April 2024

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