Sweet birch oil is steam-distilled from the bark of Betula lenta, a hardwood native to the mixed forests of eastern North America from Newfoundland south through the Appalachian highlands, producing an oil dominated by methyl salicylate (93–99%) generated through enzymatic hydrolysis of salicin-related glucosides in the bark during distillation — a biosynthetic route identical in outcome to that of wintergreen oil, though the two species are botanically unrelated. Indigenous peoples of eastern North America used the bark and sap extensively in analgesic preparations; commercial distillation peaked in the 19th century before being largely displaced by synthetic methyl salicylate production. Despite its historical importance, authentic sweet birch oil has become exceptionally rare on the commercial market: a comprehensive GC-MS authentication study of 27 commercial 'sweet birch' samples found that none contained the four confirmed natural biomarkers — o-guaiacol, veratrole, 2-E-4-Z-decadienal, and 2-E-4-E-decadienal — that distinguish genuine bark distillate from synthetic or wintergreen-derived methyl salicylate, revealing near-universal adulteration in the marketplace.^[1]