Hyperhidrosis is characterized by sweating in excess of what is required for normal temperature control. While there are many causes of hyperhidrosis, focal sweating in an otherwise healthy person is classified as primary or focal hyperhidrosis. Hyperhidrosis is not rare with the reported prevalence ranging from 1% to 3%. An epidemiological study noted a higher prevalence in women than men (62.8% vs 37.2%, respectively),1 despite the male baseline sweat rate being 30% to 40% greater after correcting for body surface.2 Gender differences in reported cases of focal hyperhidrosis may be due to underreporting by male patients. Studies have shown that men are less likely to visit their doctor or seek medical attention.3
Focal hyperhidrosis often goes unreported because of embarrassment or lack of knowledge of treatment options. In 1 survey, only 38% of patients with primary hyperhidrosis had consulted a health professional.4 Hyperhidrosis results in occupational, psychological and physical impairment, as well as potential social stigmatization.5 Excessive sweating can be a substantial burden to afflicted individuals, interfering with daily activities and causing social embarrassment. The diagnosis and effective management of primary hyperhidrosis can be challenging. Hyperhidrosis lacks concrete diagnostic tests, but a level of sweating that has an unacceptable impact on quality of life is an indication for treatment. To make a diagnosis of primary hyperhidrosis, sweating should be focal and symmetrical and lack any evidence of underlying pathology that may cause sweating as a secondary manifestation. Generalized sweating or secondary hyperhidrosis can be associated with a number of conditions or drugs.
Patients with primary hyperhidrosis have a normal density of sweat glands but seem to overproduce sweat. Most sweat glands are eccrine glands, producing a hypotonic fluid that is critical in temperature regulation. They are most dense in the palms, soles and axilla and can produce up to 10 L of sweat per day. Primary hyperhidrosis is associated with environmental and emotional triggers, such as anxiety or stress, heat, exercise, tobacco, alcohol and hot spices.
Axillary hyperhidrosis accounts for the majority of the cases of primary hyperhidrosis, followed by hands, feet, scalp and groin. Axillary hyperhidrosis is more common after the onset of puberty and is linked to the development of apocrine glands.6 The apocrine glands increase in size and number until age 18 years, at which point they comprise up to 45% of all axillary glands.7 Axillary hyperhidrosis may be associated with bromhidrosis (unpleasant odor) from bacteria that colonize the axilla and breakdown the apocrine gland secretions. Sweat glands are innervated by the sympathetic nervous system with muscarinic receptors that are activated by acetylcholine.
There are a number of available treatments for hyperhidrosis that have undergone extensive efficacy and safety evaluations. Treatment modalities include non-surgical and surgical treatments that vary in their therapeutic efficacy, side effects, cost and duration of effect. Their mechanism of action also varies, ranging from blocking sweat from reaching the skin surface, blocking the nerve signal to the sweat glands or destroying the sweat glands.
Topical antiperspirants are the most widely used treatment for hyperhidrosis. Americans spent $2.69 billion on deodorants and antiperspirants in 2011, up approximately 13% from 5 years prior, according to the market research firm Euromonitor International. Aluminum chloride topical preparations are the most widely used first-line agent. Aluminum causes the cells lining the sweat ducts to swell, occluding the duct and preventing sweat from being deposited onto the skin. Its effects are only temporary and treatment is often complicated by skin irritation.8
Blocking nerve conduction to activate sweat glands is a common treatment strategy for hyperhidrosis. Nerve conduction can be disrupted via a variety of methods including drugs, electrical currents or surgery. Botulinum toxin is the best-studied treatment for focal hyperhidrosis. Intradermal injection blocks the sympathetic cholinergic autonomic fibers innervating the sweat glands. Numerous studies, including placebo-controlled studies, have assessed the efficacy and safety of botulinum toxin in the treatment of axillary hyperhidrosis.9 All studies showed a significant treatment response by quantitative measures of sweat production or patient-reported outcome measures. Injections lead to a 75% to 100% reduction in sweat production that lasted 6 to 9 months.10 Side effects are transient, and the long-term safety profile is excellent.
Convincing evidence is lacking for other treatments that target nerve conduction. Studies have examined the use of various oral anticholinergics for primary hyperhidrosis. They act by competitive inhibition of acetylcholine at the muscarinic receptor. At the doses needed to alleviate symptoms of hyperhidrosis, systemic anticholinergic drugs also may cause adverse effects, such as dry eyes, dry mouth and problems with urinary voiding, including retention.
Iontophoresis is a process in which an electric field drives the flow of ions in a medium. The mode of action in hyperhidrosis is unclear, although an effect on nerve conduction is speculated. Iontophoresis is typically used for palmar and plantar primary hyperhidrosis. Each palm or sole is placed in a small tray filled with tap water, through which a low level of electrical current is delivered.11 Side effects include a burning sensation, erythema and small vesicle formation. Iontophoresis or systemic anticholinergic drugs may be tried before surgery in selected cases.
Surgical ablation of nerve conduction to the area of hyperhidrosis is often a last resort treatment option. Endoscopic thoracoscopic sympathectomy is the most commonly used surgical option, potentially providing permanent relief. Surgery, while effective, may result in compensatory hyperhidrosis elsewhere on the body. In a retrospective review of 170 patients who had undergone surgery, 85% of patients reported compensatory hyperhidrosis at 1 year.12 In addition, axillary hyperhidrosis does not respond as well as palmar involvement. Individuals treated for axillary hyperhidrosis without palmar involvement were significantly less satisfied with endoscopic thoracoscopic sympathectomy.
The use of surgery and heat to selectively destroy the sweat glands has become more common for the treatment of axillary hyperhidrosis. Local sweat-gland excision by subcutaneous curettage or tumescent liposuction, performed on an outpatient basis with local anesthesia, has been used successfully in recalcitrant patients. Suction curettage involves the use of an arthroscopic shaver or similar device to debride the subcutaneous tissue and clear the glands through a small (1-2 cm) incision.13 A retrospective review of 50 patients treated under general anesthesia over 5 years found a significant decrease in the mean severity score, although 6% developed recurrence. Complications included scarring, paraesthesia and infection, all of which reduced postoperative satisfaction.
Non-selective thermal destruction of sweat glands has also been used successfully to eliminate sweat glands. The MiraDry system (Miramar Labs) is a novel microwave energy device that can be used to treat axillary hyperhidrosis through selective heating of the lower layer of skin, where the eccrine and apocrine glands are located. The treatment causes irreversible thermolysis of apocrine and eccrine sweat glands. The treatment also improves patient-reported underarm odor. Patient satisfaction with the procedure is high.14 Side effects are common, including post-treatment edema, erythema and discomfort in the treatment area. Some patients experienced longer-lasting transient effects, such as altered sensation in or around the treatment area, papule and nodule formation in the axilla, fibrous band formation, muscle weakness and hair loss.
A recent report documented the use of a fractional microneedle radiofrequency (FMR) device to cause non-selective thermal destruction of sweat glands. FMR treatment was effective for the treatment of axillary hyperhidrosis without significant adverse reactions due to direct volumetric heating of the lower dermis.15
With the variety of treatment options available, patients with focal hyperhidrosis should not suffer in silence. Dermatologists should be proactive in the recognition, diagnosis and treatment of primary focal hyperhidrosis in their patients.