Some of the earliest, published studies on sweat composition date back to the 19th century.  Further studies in the 20th century began to solidify understanding of the physiology and pharmacology of the eccrine sweat gland.  In-vivo and in-vitro studies from this time period, and even those continuing today, have identified numerous structural nuances and new molecules present within sweat.  The first commercially adopted use for sweat diagnostics included testing of sodium and chloride levels in children for the diagnosis of cystic fibrosis.  Today, one of the most popular devices for this testing is the Macroduct Sweat Collection System from ELITechGroup.