1 The History of the Hygiene Hypothesis

Since the beginning of the nineteenth century there has been a gradual rise in the prevalence of immunoregulatory problems 1. For example, in 1998 about one in five children in industrialized countries suffered from allergic diseases such as asthma, allergic rhinitis or atopic dermatitis. 2 One attempt to explain the correlation between the rise in autoimmune diseases and allergies occurring during the urbanization period of the United States and parts of Europe is the Hygiene Hypothesis. The actual phrase, “Hygiene Hypothesis ” was first used by Strachan in 1989 in his discussion of hay fever and family size 2; but to fully appreciate the predictive value of this epidemiological hypothesis one must travel back to the Paleolithic period which dates to>10,000 BCE. Prior to the Neolithic period, man existed in small groups and occupied the roles of hunter, gatherer and scavenger. Because of the exposure to wild game, botanicals and carrion, the gut of early man contained a plethora of parasites, viruses, bacteria and various microbiota. This early cornucopia of microorganisms was primarily commensalistic therefore the immune system of paleolithic man did not mount a response against them. This co-existence as well as co-evolution between microbes and man explains another phrase commonly used to further explain the Hygiene Hypothesis: Old Friend