In the 1850s the main public disquiet was about adulteration that might, in one way or another, introduce poisonous or contaminating material into milk. As we have seen, this anxiety continued into the first decades of the twentieth century, with revelations about chemicals such as preservatives and colorants. Dirt was the next source of alarm, from the 1880s to the First World War. The third fear, which ran parallel with these at the end of the nineteenth century, but which overwhelmed and outlasted them both, was the hazard of infectious disease. This was not a general alarm because there were germ theory deniers even fifty years after Pasteur’s discoveries, but it was powerful for a couple of reasons. First, it seemed to match the in-depth epidemiology of epidemics, and, second, the influence of the science of bacteriology grew in the politics of public health and its interpretations became the ones acted upon. Dirt-based food hygiene eventually reinvented itself as applied bacteriology.