The history of syphilis has been well studied, but the exact origin of the disease is unknown. There are two primary hypotheses: one proposes that syphilis was carried to Europe from the Americas by the crew of Christopher Columbus as a byproduct of the Columbian exchange, while the other proposes that syphilis previously existed in Europe but went unrecognized. These are referred to as the Columbian and pre-Columbian hypotheses. Centuries before its health risks became widely known, smoking tobacco was regarded as a cure for all manner of illnesses, especially syphilis. In addition to syphilis, tobacco was a common folk remedy for a wide range of afflictions including asthma, headache, gout, cramps, female illness, and intestinal parasites.