Mar Ukva, the Reish Galusa (Exilarch of the Jewish community in Bavel) was happy to share eye salves he’d received from Shmuel, who was also a doctor, but it is better to follow Shmuel’s advice for preventing eye problems in the first place. Foods with healing properties may be eaten on Shabbos as long as they are normally eaten by healthy people for their value as food, but if only eaten to treat minor ailments, they’re prohibited on Shabbos. This also applies to topical ointments and even immersion in the ocean. If done for pleasure, ok, if done for therapy not permitted on Shabbos. Note that this does not address restrictions on Shabbos bathing and swimming derived from other areas of the law like throwing water in the public domain or wringing out one’s bathing suit. We may not dip a wounded hand or foot in vinegar on Shabbos to stop the bleeding UNLESS the wound occurs on the back of the hand or foot, which is considered dangerous. REM: we always override Shabbos to save life or treat dangerous conditions. The seeming “folk remedies” of the rabbis were derived from sophisticated but small scale trial and error processess over long period of time. The “snake of the Rabbis” refers to a snakebite orchestrated by Heaven as a punishment for violating Rabbinic decrees,and for this bite there is no cure.