When Lynch fed these dog-associated dust microbes to mice, she found that the rodents became less sensitive to various allergens. The dusty meals also increased the numbers of over 100 bacterial species in the rodents’ guts, at least one of which could protect the mice from allergens. This is the essence of the hygiene hypothesis and its various spin-offs: exposure to a broader range of microbes can change the microbiome and suppress allergic inflammation – at least in mice.
