The Ancient World, C. 500 B.c.e. –200 C.e.
In Greek mythology Hygeia was one of the daughters of Aesculapius, a renowned healer and demigod; she was considered the goddess of health. The Greek word hygiene hygieinē meant "sound, healthy, or strong," and was possibly related to the Sanskrit ugias, or "strength." In the works of Greek physicians, from Hippocrates (460–c. 377 B.C.E.) onward, hygiene was that branch of medicine dedicated to the "art of health," distinguished by Galen (129–c. 199 C.E.) from its other arm, therapeutics, or the treatment of disease. The Greeks understood the world to be composed of four elements—earth, air, fire, and water—and, analogously, understood life to be controlled by the four principles of hot and cold, wet and dry, which corresponded to the four "humors" that composed the body: yellow and black bile, blood, and phlegm. The body was understood holistically as a dynamic state of interaction between these four principles, whose imbalance could cause disease. The goal of hygienic practice was to achieve qualitative and humoral balance within the body, and thus for each person to live out their allotted lifespan.
Hygienic instruction was tailored to each individual's constitution, itself the result of humoral activity, and to their environmental and personal circumstances, such as age, sex, status, and relations with others. Proper hygiene included regulations concerning sexual activity, sleeping and waking, bathing, exercise (a central activity for freeborn Greeks), and above all, diet. Dietary regimens were extremely detailed as to when it was or was not appropriate to eat particular kinds of animals or grains and considered food very carefully in all its cooked and raw states, discussing strategies such as boiling, grilling, roasting, and breading that would moisten, dry, heat, and bind. Because food was considered to have such powers in altering a person's internal humoral balance, the distinction between hygiene and therapeutics was blurred, as the same foods could be prescribed to cure disease as well as maintain health. Although the Greek physicians regarded their work as purely empirical, in contrast to superstitious medical practices such as appeasing angry gods, their texts clearly equated healthy practices with the moral order of their culture: a hygienic person went with his fellows to the gymnasium, was abstemious with alcohol, and had only acceptable sexual relations.
The Greeks' conception of the body as an organic whole integrated into its environment, and their regimen-based methods of preserving health by achieving harmony within the body, were remarkably similar to health systems that apparently coincidentally evolved in India and China. Though their explanatory frameworks differ from the Greeks and from each other, both Indian Ayurvedic medicine and traditional Chinese medicine have longevity and prolonged states of health as their goal, and both discuss which substances, qualities, and actions are life-enhancing and which are not. Because of these similarities, the word hygiene is sometimes inaccurately used to refer to these traditions in English-language medical histories of these peoples.