Anthropologists have three main ways of looking at the culture of biomedicine. First is the institutional history of biomedicine which describes how biological facts change over time. Next is the language of biomedicine and how social values and ideologies are re-conceptualized in a more scientific manor. Last are the rituals of biomedicine in which anthropologists look at ill individuals in places like clinics. Through germ theory, fundamental genetics, and pharmaceutical use, the way we as society look at our specific culture of biomedicine has changed in a big way. Without an individual ideology for how medicine is used in ones specific culture, we would have a much more difficult time diagnosing the illness at hand.
In my opinion, dichotomy simply comes from two separate sides of a specific spectra. In many cases, dichotomy comes from a specific social class you are considered to be apart of. With that, a certain culture may consider someone to be sick based of individual judgement of themselves whereas another culture may only consider one sick once diagnosed as such by a medical professional. In a culture with more poverty, it may be more likely for someone to consider one self sick without acknowledgement from a local doctor and without knowing the specific source of illness.
With dichotomy, either something is one way or it is the opposite. In the case of sick and healthy persons in western society, I believe it comes down to ones clarification of their own negative well-being versus how they feel well considering themselves healthy. Much of society has a feeling inside of what they consider healthy and without this “normal” sense of self, an individual can then be considered sick (such as a cold whereas most people do not seek medical help).
Sickness becomes much more logical to society once diagnosed by a medical practitioner. Generally, Western society tends to trust and rely on a health professional for diagnosis and even more so when the illness can be diagnosed by specific name known to most of society (i.e. influenza, chicken-pox, ect.).