She made a very influential analysis of concepts of dirt, purity/impurity, the sacred, clean/unclean across different societies and times in Purity and Danger (1966). That it's not about literal filth but all sorts of factors are involved.

E.g. how dare Ignaz Semmelweiss imply that surgeons could be carrying impurity? (because men, status, etc).

(I recently saw a very good tweet thread applying this to people's attitudes to pandemic risks, sigh - 'My friends could not possibly be carrying contagion....')