Merck Manual

Please confirm that you are a health care professional

honeypot link



Shinjita Das

, MD, Harvard Medical School

Last full review/revision Jun 2020| Content last modified Jun 2020
Click here for Patient Education
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 wipes, oral glycopyrrolate or oxybutynin, botulinum toxin, microwaved-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 occurs around the lips and mouth when ingesting foods and beverages that are spicy or hot in temperature. There is no known cause in most cases, but gustatory sweating can be increased in diabetic neuropathy, facial herpes zoster, cervical sympathetic ganglion invasion, central nervous system injury or disease, or parotid gland injury. In the case of parotid gland injury, surgery, infection, or trauma may disrupt parotid gland innervation and lead to regrowth of parotid parasympathetic fibers into sympathetic fibers innervating local sweat glands in skin where the injury took place, usually over the parotid gland. This condition is called Frey syndrome. Asymmetric sweating can be caused by a neurologic abnormality.

Other causes of focal sweating include pretibial myxedema (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




Central nervous system

Trauma, autonomic neuropathy


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

Endocrine disorders

Hyperthyroidism, hypoglycemia, excessive secretion of sex hormones caused by gonadotropin-releasing hormone (GnRH) agonists




* 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) or in a semiquantitative way when following the course of treatment. Asymmetry in the pattern of sweating suggests a neurologic cause.

Laboratory tests to identify a cause of hyperhidrosis are guided by the patient's other symptoms and might include, for example, complete blood count to detect leukemia, serum glucose to detect diabetes, and thyroid-stimulating hormone to screen for thyroid dysfunction.

Treatment of Hyperhidrosis

  • Aluminum chloride hexahydrate solution

  • Topical glycopyrronium

  • Tap-water iontophoresis

  • Oral anticholinergic drugs

  • Botulinum toxin type A

  • Microwaved-based device

  • Surgery

Initial treatment of focal and generalized sweating is similar.

Aluminum chloride hexahydrate 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 2.4% cloth wipes can be used to treat primary axillary hyperhidrosis (1). 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 anticholinergic drugs may help some patients. Glycopyrrolate or oxybutynin can be used to decrease sweating but can be limited by anticholinergic adverse effects, including dry mouth, dry skin, flushing, blurred vision, urinary retention, mydriasis, and cardiac arrhythmias.

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 microwaved-based device (eg, miraDry®) heats and subsequently permanently destroys 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. 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 about Hyperhidrosis

  • Asymmetric hyperhidrosis suggests a neurologic cause.

  • Although diffuse 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, 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.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Also of Interest