Page 988 - Veterinary Immunology, 10th Edition

VetBooks.ir The Hygiene Hypothesis

The prevalence of allergic disease has increased significantly in
Western societies over the past 50 years. While most obvious in

humans, this has also affected domestic species, especially dogs and
cats. It is likely that this increase is a result of changes in the body's
microbiota (Fig. 30.1). The hygiene hypothesis suggests that
alterations in Western diets, environmental cleanliness, an urban
lifestyle, and overuse of antibiotics together cause long-term

changes in the intestinal microbiota that have driven the increases
in allergic and inflammatory disease. Since the intestinal microbiota
normally influence the Th1/Th2 balance, it is suggested that this

dysbiosis causes, Th2 responses to predominate and results in the
development of allergies. Additionally, the skin and lung
microbiota affect the development of lung and skin allergies.

FIG. 30.1 The hygiene hypothesis. A lack of microbial diversity in

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