Should you take your shoes off in someone else's house?

The etiquette answer and the evidence answer agree here, which is unusual for a household argument. Offer to remove your shoes on arrival and let the host wave you off if they do not care. That default costs nothing, and it respects the fact that shoes-off is the firm norm across most of Asia, much of Northern Europe, Canada, and many households everywhere else, so assuming shoes-on is a local convention rather than a universal one.

The hygiene case is more concrete than people expect. Microbiology testing has repeatedly found large bacterial loads on shoe soles, with one widely cited University of Arizona study detecting coliform bacteria on the large majority of shoes tested and E. coli on a substantial share. Household dust studies have also traced lead, pesticides, coal tar residue from sealed driveways, and other outdoor contaminants indoors primarily via footwear, which matters most in homes with crawling infants who spend their time on the floor with their hands in their mouths. The counterarguments are real but limited: some people need supportive footwear for foot or back conditions, formal entertaining sometimes calls for shoes, and a host who does not care should not be argued with. Hosts who do care should say so warmly and have a basket by the door rather than a sign.