This paper is informed by the recent attempts to construct Marxist views of nature, by the lively historical work on 19th-century British class structure, and by the dedicated work of feminist historians of medicine. Using the common disease of adolescent girls, chlorosis, as an example of a real "physical" illness, I shall argue that disease is, in part, socially constructed. Not only is the social class of both doctor and patient an important determinant in the perception of illness, but so too is the relationship between the disease and the mode of production. Both the "existence" of chlorosis and the way it was understood served ideologically to conceal the growing importance of adolescent labor and the recognition of the social genesis of illness. In doing so, chlorosis was similar to other forms of chronic illness. In a time when the conditions of work were strikingly insalubrious, the etiological emphasis was on individual failure, not on physical or social conditions of work. I argue that notions of health and disease partake of the struggles and social relations of the society that sustains them, but in a way which hides that very social nature. In this sense, they are like Marx's concept of a commodity--and in being a commodity, diseases appear not to embody social relations, but rather to be part of nature. I suggest that we see this "nature" in part as a commodity fetish--something we construct as "other" for a reason--and that we rediscover the social in the natural.