According to the History of Anaesthesia Society, anesthesia was first used in the 13th century by Theodoric of Lucca. This Italian physician used sponges soaked in opium to relieve pain during surgery.
HowStuffWorks explains that opium and alcohol were the main types of anesthetic used up until the 1840s. In 1846, Dr. William Morton revealed that the use of ether rendered patients unconscious before dental surgery. Other doctors also claimed to have used ether during the 1840s. Other early forms of anesthetic include nitrous oxide, which was first used in 1845, and chloroform, which was used during the 19th century.