The NHS once did a survey of nurses. Those with the most potentially dangerous infections carried on their hands (we all carry germs, the MRSA germ lives quite happily on some people all the time) were those who were wearing rings. The germs would be left under the ring when washing hands and not being careful about washing under jewellery.

This problem has been semi-fixed by the wearing of latex gloves and by better cleansers, but wearing rings, especially rings with uneven surfaces (engraved, pierced, gem settings etc.) is frowned upon and in some wards, forbidden.

As for being dictated to.... if you were being handled by someone, be it a masseuse, nurse, chiropodist or proctologist, would you like it if you got scratched by their 18ct square cut cluster setting in a place you couldn't reach to put a sticky plaster on? It's a common sense thing, not just for the clean, corporate image.

LTS