In 1874, the Heyden Company located near Dresden, Germany began manufacturing and selling synthetic salicylic acid. Acetylated salicylic acid, the active product in salves and teas, was made from willow bark and other plant materials. Chemist Hermann Kolbe had synthesized salicylic acid in 1859, after figuring out the chemical structure. Synthetic salicylic acid was cheaper than the extract from willow bark, but had some adverse effects such as gastrointestinal irritation.