Carbon dioxide, along with being the final product of metabolism and a basic ingredient of photosynthesis, is also a remedy which when applied to the skin has effects that are empirically held in high regard. Already in the Middle Ages, acidic water and gases vented from the ground (carbon dioxide fumaroles) were recognized to have strong curative powers and to be effective against “St. Anthony’s fire” caused by ergot poisoning which often occurred at the time. There was no other effective method of treatment. In 1624, the medical scholar van Helmont (1577–1644) confirmed that these gases contained carbon dioxide. The anti-infective properties of carbon dioxide were discovered and analyzed by Boyle (1627–1691) and Lavoisier (1743– 1794). The first systematic medical research of CO2 use was conducted by Lalouette (1777), who showed that chronic and inveterate skin damage is cured by the serial application of CO2. Areas where CO2-enriched water emerges naturally from the ground developed in the 19th century into curative spas for the heart. Because the method of using such water involved volumetric loading (pre-loading) in a full water bath, this at one point essentially appeared to fall out of date. However, the application of CO2 to the skin gained a suitable degree of acceptance based on the experiences of physicians, and eventually came to be used as an effective mode of treatment for circulatory disorders, vascular disorders and disorders of autonomic function and regulation. The treatments took advantage of local features such as a spa cure or were carried out using “carbon dioxide springs” or (artificial) therapeutic CO2 officially recognized as medications (Jordan, 1985). Treatment involving the oral administration of CO2- enriched water, that is, the drinking of carbonated water, is also sometimes carried out.