Is "allopathy" pejorative?
The word has no real meaning outside of the context of homeopathy. It's rather pejorative in that context. It's rather irrelevant in any other.
There are two kinds of practicing physicians in the United States: allopathic physicians (MD's) and osteopathic physicians (DO's). Both are fully licensed physicians, trained in diagnosing and treating illnesses and disorders, and in providing preventive care.
-Indiana University Bloomington web page
Modern medicine generally refers to clinical practice: the diagnosis, treatment and prevention of disease by a physician. That physician may be an allopathic physician (M.D.) or an osteopathic physician (D.O.).
-Explore Health Careers web page
It seems to me that these web pages intend to use neutral language.
Apparently, osteopathy is a later development than allopathy, and a reaction to allopathy, intended to promote whole-body health and preventive strategies and to reduce treatment with medicine. The distinction does still exist today, both in training and in practice; but in general allopaths and osteopaths perform the same roles (prescribing drugs, performing surgery, etc.) in every state, and they often make similar decisions.
In my personal experience in a family of MD’s, the culture of medicine is like this: MD’s and DO’s consider each other to be equals in the first rank of competence. For example they would be likely to assume that an ophthalmologist (regardless of whether he is an MD or a DO) would be preferable to an optometrist. And they would generally consider in one category such people as acupuncturists, chiropractors or homeopaths, people who apparently have an occasional success for reasons that nobody really understands, and so are worth considering for a patient who cannot be treated successfully and wants to try that route.
Allopathy is mostly used pejoratively. But in the United States it sometimes is used non-pejoratively. The connotation depends on context.
In its literal sense, allopathy is not pejorative. It is a technical term, part of an unscientific disease theory that “like cures like”. It was coined by Samuel Hahnemann (in German, later borrowed into English). It was part of his classification system of all drug treatments according to the symptoms the drugs would be expected to cause in a healthy person:
homeopathic treatments produce symptoms resembling those produced by the disease (hómoios, “resembling”)
enantiopathic treatments produce symptoms opposite to those produced by the disease (enantíos, “opposing”)
allopathic treatments produce symptoms neither resembling nor opposite to those produced by the disease (állos, “other”)
But in practice, allopathy is used by Hahnemann’s disciples as a dismissive label for all medical practices that do not follow the “like cures like” theory, and therefore are supposedly useless or harmful. In the same way, someone might dismissively refer to surgery they consider useless or harmful as butchery or bloodletting. (At one time, bloodletting was common medical practice, based on the unscientific theory that the cause of disease is imbalance of bodily fluids.*)
Recently in the United States, the term allopathic medicine has begun to be used with no pejorative connotation as an antonym of osteopathic medicine. In this context, allopathic medicine means medicine as practiced by Doctors of Medicine, and osteopathic medicine means medicine as practiced by Doctors of Osteopathy. This is arguably a very loose or figurative usage, because osteopathic is not opposite to allopathic – it is not a Hahnemann classification at all. Osteopathic treatments were based on yet another unscientific theory, that disease is caused by problems in the bones and muscles and can be reversed by manipulating joints and tissues. Arguably Hahnemann would have considered osteopathy just another useless allopathic practice.
For more information, see the Wikipedia articles “Homeopathy”, “Allopathic medicine”, and “Osteopathic medicine in the United States”.
* “You know, medicine is not an exact science, but we are learning all the time. Why, just fifty years ago, they thought a disease like your daughter’s was caused by demonic possession or witchcraft. But nowadays we know that Isabelle is suffering from an imbalance of bodily humors, perhaps caused by a toad or a small dwarf living in her stomach.” (“Theodoric of York, Medieval Barber”, Saturday Night Live, season 3, episode 18)