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HYPERHIDROSIS, A CONDITION CHARACTERIZED by excessive sweating, can be generalized or focal. Generalized hyperhidrosis involves the entire body and is usually part of an underlying condition, most often an infectious, endocrine or neurologic disorder. Focal hyperhidrosis is idiopathic, occurring in otherwise healthy people. It affects 1 or more body areas, most often the palms, armpits, soles or face. Almost 3% of the general population, largely people aged between 25 and 64 years, experience hyperhidrosis. The condition carries a substantial psychological and social burden, since it interferes with daily activities. However, patients rarely seek a physician’s help because many are unaware that they have a treatable medical disorder. Early detection and management of hyperhidrosis can significantly improve a patient’s quality of life. There are various topical, systemic, surgical and nonsurgical treatments available with efficacy rates greater than 90%–95%. CMAJ 2005;172(1):xxx-xx D O I: 10 .1 50 3/ cm aj .1 04 07 08 tion in response to finger immersion in cold water. Such an increased sympathetic activity through the T2–T3 ganglia could cause palmar hyperhidrosis. Excessive palmar and plantar sweating could thus result in a vicious cycle, as evaporative cooling of the skin increases sympathetic outflow through reflex action, which in turn increases sweat output. Parasympathetic dysfunction was implicated in a study that compared heart rate variability in patients with focal hyperhidrosis with that of healthy control subjects. The authors found that, although sympathetic activity seemed to be similar, patients with focal hyperhidrosis exhibited heart rate patterns suggesting parasympathetic dysfunction. Diagnosis and clinical presentation The first step in the evaluation of hyperhidrosis is to differentiate between generalized and focal hyperhidrosis. Generalized hyperhidrosis is usually part of some other underlying condition, such as infective or malignant disease or a hormonal disorder, and focal or primary idiopathic hyperhidrosis occurs in otherwise healthy people (Box 1). It usually peaks in the second or third decade of life and manifests as bilateral excessive sweat production confined to the armpits, soles of the feet, palms of the hands, face or other specific sites. Gustatory sweating (Frey’s syndrome) is also a form of focal hyperhidrosis. A positive family history is evident in 30%–50% of patients. Furthermore, patients with focal hyperhidrosis generally do not sweat during sleep. Thus, a medical history focusing on location of excessive sweating, duration of the presentation, family history, age at onset and the absence of any apparent cause allows one to easily differentiate focal from generalized hyperhidrosis (Box 2). Although there is no standard definition of focal hyperhidrosis, less than 1 mL/m of sweat production per minute by eccrine glands at rest and at room temperature is considered normal. Alternatively, sweat rates of discrete anatomic areas (e.g., palm, axilla) may be measured for research purposes (e.g., normal sweat rates for the axilla are < 20 mg/min). For practical clinical purposes, any degree of sweating that interferes with the activities of daily living should be viewed as abnormal. Diagnosis of focal hyperhidrosis does not require laboratory investigations. A starch iodine test can be used to outline the area of excessive sweating (Fig. 1). Iodine solution (1%–5%) is applied to a dry surface, and after a few seconds starch is sprinkled over this area. The starch and iodine interact in the presence of sweat, leaving a purplish sediment. This purple area identifies the duct of the sweat gland. Although the starch iodine test is not necessary for diagnosis, it allows the qualitative identification of areas of excessive sweating, which can be recorded by pictures taken before and after treatment. Psychosocial impairment is a significant aspect of focal hyperhidrosis (Box 3). In a US survey, one-third of patients with axillary hyperhidrosis reported their sweating as being barely tolerable or intolerable and as frequently interfering with activities of daily living; 35% of patients reported a decrease in leisure activity time due to excesHaider and Solish 2 JAMC • 4 JANV. 2005; 172 (1) Box 1: Causes of generalized and focal hyperhidrosis