Introduction: The changing microbial environment, Darwinian medicine and the hygiene hypothesis -- The paleolithic disease-scape, the hygiene hypothesis, and the second epidemiological transition -- Immunoregulation by microbes and parasites in the control of allergy and autoimmunity -- Hepatitis A virus, TIM-1 and allergy -- Linking lifestyle with microbiota and risk of chronic inflammatory disorders -- Soil bacteria, nitrite and the skin -- The hygiene hypothesis and allergic disorders -- Multiple sclerosis -- Inflammatory bowel disease and the hygiene hypothesis: an argument for the role of helminths -- The hygiene hypothesis and Type 1 diabetes -- The hygiene hypothesis and affective and anxiety disorders -- Immune regulation in atherosclerosis and the hygiene hypothesis -- The ‘delayed infection’ (aka ‘hygiene’) hypothesis for childhood leukaemia -- Is there room for Darwinian medicine and the hygiene hypothesis in Alzheimer pathogenesis? -- Alternative and additional mechanisms to the hygiene hypothesis.

Man has moved rapidly from the hunter-gatherer environment to the living conditions of the rich industrialised countries. The hygiene hypothesis suggests that the resulting changed and reduced pattern of exposure to micro-organisms has led to disordered regulation of the immune system, and hence to increases in certain chronic inflammatory disorders. The concept began with the allergic disorders, but there are now good reasons for extending it to autoimmunity, inflammatory bowel disease, atherosclerosis, depression associated with raised inflammatory cytokines, some cancers and perhaps neuroinflammatory disorders such as Alzheimer’s and Parkinson’s. This book discusses the evidence for and against in the context of Darwinian medicine, which uses knowledge of evolution to cast light on human diseases. It is the first book to consider the broader implications of the hygiene hypothesis in areas of medicine where it has not previously been applied. The approach is interdisciplinary, looking at man’s microbiological history, at the biology of the effects of microorganisms on the immune system, and at the implications for chronic inflammatory disorders in multiple organ systems. Finally, the authors describe progress in the exploitation of microorganisms or their components as novel prophylactics and treatments in several branches of medicine.