"one who practices allopathy," 1830, a back-formation from allopathy or else from German allopath (1823).
Entries linking to allopath
allopathy n.
1836, "treatment of disease by remedies that produce effects opposite to the symptoms," from German Allopathie (Hahnemann), from Greek allos "other" (from PIE root *al- "beyond") + -patheia, "suffering, disease, feeling" (see -pathy). It is the term applied by homeopathists to traditional medicine. A word unloved by classicists; it is malformed and the equivalent Greek compound had a different sense and was used in grammar, etc.