Homeopathy, hoh mee OP uh thee, is a system of medical practice based on the attempt to "let like cure like." According to homeopathic physicians, a substance that produces certain symptoms in a healthy individual will cure those symptoms in a sick individual. Poison ivy, for example, causes rashes. Homeopathic physicians thus treat rashes with poison ivy. Onions cause crying and a watery discharge from the nose. Therefore, onions are used to treat colds. Samuel Hahnemann, a German physician, developed homeopathy in the late 1700's (see Hahnemann, Samuel).