Hyperhidrosis (Hh, sometimes called “excessive sweating”) is a disorder of uncontrollable, extreme, episodic, unexpected sweating beyond what’s considered “normal” or is necessary to maintain thermal homeostasis or as a reaction to stress. Individuals with Hh may sweat four or five times more than “average.” 
There are two main categories of Hh: Primary idiopathic hyperhidrosis and secondary hyperhidrosis.
Patients with Hh can have excessive sweating either over localized areas (called focal areas) or over the entire body (generalized). Typically, primary idiopathic hyperhidrosis is focal in nature while secondary hyperhidrosis is more likely to manifest as generalized sweating.
Focal areas commonly affected by primary Hh include: the soles, palms, axillae, craniofacial region, groin, buttocks, or other distinct body regions. Combinations of focal areas are commonly seen. For example, research shows that 81% of axillary hyperhidrosis sufferers indicate that they sweat excessively from three or more additional focal areas.
Based on data published in 2016, there are approximately 15.3 million individuals (or 4.8% of the population) living with hyperhidrosis (Hh) in the U.S. 
This makes Hh more common than autism, melanoma, psoriasis, and peanut allergies.163-6
While primary Hh is a condition unto itself, secondary hyperhidrosis symptoms are due to one of a large number of underlying medical conditions, including endocrine disorders, neurological problems, use of certain drugs, cancer, chronic infections, dermatologic syndromes, and conditions associated with excess catecholamine discharge. Occasionally, hyperhidrosis can be related to eating (gustatory sweating) or secondary to parotid surgery or diabetes.[83,111] Secondary Hh may also occur as a side effect of a medication.
162. Doolittle J, Walker P, Mills T, Thurston J. Hyperhidrosis: an update on prevalence and severity in the United States. Archives of Dermatological Research. 2016;308(10):743-749. doi:10.1007/s00403-016-1697-9.
163. Key statistics for melanoma skin cancer. American Cancer Society website. https://www.cancer.org/cancer/melanoma-skin-cancer/about/key-statistics.html. Jan. 4, 2018. Accessed April 18, 2018.
164. How common is psoriasis worldwide? NEJM Journal Watch website. https://www.jwatch.org/jd201211090000002/2012/11/09/how-common-psoriasis-worldwide. Nov. 9, 2012. Accessed April 18, 2018.
165. Food allergy facts and statistics. Food Allergy Research & Education website. https://www.foodallergy.org/sites/default/files/migrated-files/file/facts-stats.pdf. Accessed April 18, 2018.
166. Autism Spectrum Disorder (ASD) Data & Statistics. Centers for Disease Control and Prevention website. https://www.cdc.gov/ncbddd/autism/data.html. Feb. 12, 2018. Accessed April 19, 2018.
167. Glaser DA, Ballard AM, Hunt NL, Pieretti LJ, Pariser DM. Prevalence of Multifocal Primary Hyperhidrosis and Symptom Severity Over Time: Results of a Targeted Survey. Dermatol Surg. 2016 Dec;42(12):1347-1353.