Merck Manual

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Shinjita Das

, MD, Harvard Medical School

Reviewed/Revised Apr 2022 | Modified Sep 2022
Topic Resources

Hyperhidrosis is excessive sweating, which can be focal or diffuse and has multiple causes. Sweating of the axillae, palms, and soles is most often a normal response due to stress, exercise, or environmental heat; diffuse sweating is usually idiopathic but, in patients with compatible findings, should raise suspicion for cancer, infection, or endocrine disease. Diagnosis is obvious, but tests for underlying causes may be indicated. Treatments include topical aluminum chloride, tap-water iontophoresis, glycopyrronium tosylate wipes, oral glycopyrrolate or oxybutynin, botulinum toxin, a microwave-based device, and, in extreme cases, surgery.

Etiology of Hyperhidrosis

Hyperhidrosis can be focal or generalized.

Focal sweating

Emotional causes are common, causing sweating on the palms, soles, axillae, and forehead at times of anxiety, excitement, anger, or fear. It may be due to a generalized stress-increased sympathetic outflow. Sweating is also common during exercise and in hot environments. Although such sweating is a normal response, patients with hyperhidrosis sweat excessively and under conditions that do not cause sweating in most people.

Gustatory sweating (sweating in response to or in anticipation of eating) can result from a number of causes; however, most often the cause is unknown. For example, sweating around the lips and mouth can occur when ingesting foods and beverages that are spicy or hot in temperature. Pathologic causes include diabetic neuropathy Diabetic Neuropathy In patients with diabetes mellitus, years of poorly controlled hyperglycemia lead to multiple, primarily vascular, complications that affect small vessels (microvascular), large vessels (macrovascular)... read more Diabetic Neuropathy , facial herpes zoster Herpes Zoster Herpes zoster is infection that results when varicella-zoster virus reactivates from its latent state in a posterior dorsal root ganglion. Symptoms usually begin with pain along the affected... read more Herpes Zoster , cervical sympathetic ganglion invasion, central nervous system injury or disease, or parotid gland injury. Frey syndrome is a neurologic condition due to injury to or around the parotid glands resulting from surgery, infection, or trauma. Frey syndrome disrupts the auriculotemporal nerve, with subsequent inappropriate regeneration of parotid parasympathetic fibers into sympathetic fibers innervating local sweat glands in skin where the injury took place. As a result, the misplaced parasympathetic fibers (which normally cause salivation as a gustatory response) now instead trigger sympathetic fibers that cause (inappropriate) redness and sweating of the preauricular cheek.

Other causes of focal sweating include pretibial myxedema Hypothyroidism Hypothyroidism is thyroid hormone deficiency. Symptoms include cold intolerance, fatigue, and weight gain. Signs may include a typical facial appearance, hoarse slow speech, and dry skin. Diagnosis... read more Hypothyroidism (shins), hypertrophic osteoarthropathy (palms), blue rubber bleb nevus syndrome, and glomus tumor (over lesions). Compensatory sweating is intense sweating after sympathectomy.

Generalized sweating

Generalized sweating involves most of the body. Although most cases are idiopathic, numerous conditions can be involved (see table Some Causes of Generalized Sweating Some Causes of Generalized Sweating Some Causes of Generalized Sweating ).


Some Causes of Generalized Sweating




Central nervous system

Trauma, autonomic neuropathy


Antidepressants, aspirin, nonsteroidal anti-inflammatory drugs, hypoglycemic agents, caffeine, theophylline; opioid withdrawal

Endocrine disorders




* Primarily nocturnal generalized sweating (night sweats).

Symptoms and Signs of Hyperhidrosis

Sweating is often present during examination and sometimes is extreme. Clothing can be soaked, and palms or soles may become macerated and fissured.

Hyperhidrosis can cause emotional distress to patients and may lead to social withdrawal. Palmar or plantar skin may appear pale.

Diagnosis of Hyperhidrosis

  • History and examination

  • Iodine and starch test

  • Tests to identify a cause

Hyperhidrosis can be primary or secondary to an underlying medical condition. It is diagnosed by history and examination but can be confirmed with the iodine and starch test. For this test, iodine solution is applied to the affected area and allowed to dry. Cornstarch is then dusted on the area, which makes areas of sweating appear dark. Testing is necessary only to confirm foci of sweating (as in Frey syndrome, or to locate the area needing surgical or botulinum toxin treatment Treatment ) or in a semiquantitative way when following the course of treatment. Asymmetry in the pattern of sweating suggests a neurologic cause.

Treatment of Hyperhidrosis

  • Aluminum chloride hexahydrate solution

  • Topical glycopyrronium tosylate

  • Tap-water iontophoresis

  • Oral anticholinergic drugs

  • Oral clonidine

  • Botulinum toxin type A

  • Microwaved-based device

  • Surgery

Initial treatment of focal and generalized sweating is similar.

Aluminum chloride hexahydrate (an antiperspirant) 6 to 20% solution in absolute ethyl alcohol is indicated for topical treatment of axillary, palmar, and plantar sweating; these preparations require a prescription. The solution precipitates salts, which block sweat ducts. It is most effective when applied nightly and should be washed off in the morning. Sometimes an anticholinergic drug is taken before applying to prevent sweat from washing the aluminum chloride away. Initially, several applications weekly are needed to achieve control, then a maintenance schedule of once or twice a week is followed. If treatment under occlusion is irritating, it should be tried without occlusion. This solution should not be applied to inflamed, broken, wet, or recently shaved skin. High-concentration, water-based aluminum chloride solutions may provide adequate relief in milder cases.

Glycopyrronium tosylate (an anticholinergic drug) 2.4% cloth wipes can be used to treat primary axillary hyperhidrosis in people 9 years of age and older (1 Treatment reference Hyperhidrosis is excessive sweating, which can be focal or diffuse and has multiple causes. Sweating of the axillae, palms, and soles is most often a normal response due to stress, exercise... read more ). Caution should be used in patients who are sensitive to anticholinergic drug effects.

Tap-water iontophoresis, in which salt ions are introduced into the skin using electric current, is an option for patients unresponsive to topical treatments. The affected areas (typically palms or soles) are placed in tap-water basins each containing an electrode across which a 15- to 25-mA current is applied for 10 to 20 minutes. This routine is done daily for 1 week and then repeated weekly or bimonthly. Iontophoresis may be made more effective by dissolving anticholinergic tablets (eg, glycopyrrolate) into the water of the iontophoresis basins. Although the treatments are usually effective, the technique is time-consuming and somewhat cumbersome, and some patients tire of the routine.

Oral clonidine is an alpha-2-adrenergic agonist that decreases sweating mediated by sympathetic nervous system activity.

Botulinum toxin type A is a neurotoxin that decreases the release of acetylcholine from sympathetic nerves serving eccrine glands. Injected directly into the axillae, palms, or forehead, botulinum toxin inhibits sweating for about 5 months depending on dose. Of note, botulinum toxin is approved by the U.S. Food and Drug Administration only for axillary hyperhidrosis and may not be covered by insurance for other sites of hyperhidrosis. Complications include local muscle weakness and headache. Injections are effective but painful and expensive, and treatment must be repeated 2 to 3 times per year.

A microwave-based devicecan heat and subsequently permanently destroy sweat glands. Patients may benefit from two treatments at least 3 months apart.

Surgery is indicated if more conservative treatments fail. Patients with axillary sweating can be treated with surgical excision of axillary sweat glands through open dissection or by liposuction (the latter appears to have lower morbidity). Patients with palmar sweating can be treated with endoscopic transthoracic sympathectomy. The potential morbidity of surgery must be considered, especially in sympathectomy. Potential complications include phantom sweating (a sensation of sweating in the absence of sweating), compensatory hyperhidrosis (increased sweating in untreated parts of the body), gustatory sweating, neuralgia, and Horner syndrome Horner Syndrome Horner syndrome is ptosis, miosis, and anhidrosis due to dysfunction of cervical sympathetic output. (See also Overview of the Autonomic Nervous System.) Horner syndrome results when the cervical... read more Horner Syndrome . Compensatory hyperhidrosis is most common after endoscopic transthoracic sympathectomy, developing in up to 80% of patients, and can be disabling and far worse than the original problem.

Treatment reference

  • 1. Glaser DA, Hebert AA, Nast A, et al: Topical glycopyrronium tosylate for the treatment of primary axillary hyperhidrosis: Results from the ATMOS-1 and ATMOS-2 phase 3 randomized controlled trials. J Am Acad Dermatol pii:S0190-9622(18)32224-2, 2018. doi: 10.1016/j.jaad.2018.07.002

Key Points

  • Hyperhidrosis can be focal or generalized.

  • Asymmetric hyperhidrosis suggests a neurologic cause.

  • Although generalized sweating is usually normal, consider cancer, infection, and endocrine disorders as directed by patient symptoms.

  • Obtain laboratory tests to determine systemic causes based on clinical findings.

  • Treat using aluminum chloride solutions, tap-water iontophoresis, topical glycopyrronium tosylate, oral glycopyrrolate or oxybutynin, botulinum toxin, or a microwaved-based device.

  • Consider surgical options in patients who do not respond to drug or device therapy; these include excision of axillary sweat glands and endoscopic transthoracic sympathectomy for palmar sweating, which carries risk of significant adverse effects.

Drugs Mentioned In This Article

Drug Name Select Trade
Drysol, Hypercare, Xerac AC
Cuvposa, Dartisla, Glycate, GLYRX-PF, Lonhala Magnair, Robinul, Robinul Forte, Seebri Neohaler
Ditropan, Ditropan XL, Gelnique , Oxytrol, Oxytrol for Women
Catapres, Catapres-TTS, Duraclon, Kapvay, NEXICLON XR
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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