Diagnosis of primary localised hyperhidrosis

Diagnosis of primary focal hyperhidrosis should be made only after exclusion of an underlying cause for the excessive sweating (secondary hyperhidrosis).

Typical features of primary localised (focal) hyperhidrosis are focal, visible sweating of at least 6 months' duration without apparent cause and with at least two of the following features:

• bilateral and roughly symmetrical sweating;
• sweating that impairs daily activities;
• excessive sweating at least once each week;
• age of onset less than 25 years;
• positive family history;
• or cessation of focal sweating during sleep (1)

In the absence of an obvious underlying cause on history and examination, patients with characteristic presentation for primary focal hyperhidrosis, do not require further investigations (1).

Secondary hyperhidrosis should be suspected in patients with:

• generalised sweating
• predominantly night-time sweating (haematological cancer or infection, such as tuberculosis)
• use of drugs with related side effects
• history of illicit drug use
• weight loss (cancer)
• palpitations (thyrotoxicosis)
• feeling systemically unwell (1)

Specialist investigations may be undertaken to allow mapping of the pattern of hyperhidrosis e.g.

• the Minor's iodine starch test - involves painting the affected area with iodine solution and allowing it to dry before dusting with starch powder. Areas of sweating become purple as the sweat dissolves the starch, which reacts with the iodine
• gravimetry - measures the weight of liquid produced in one area in a given period, not used as a formal diagnostic test (1).

Reference:

• (1) Benson RA, Palin R, Holt PJ, Loftus IM. Diagnosis and management of hyperhidrosis. BMJ. 2013;347:f6800