The Kitzur Shulchan Aruch was written in the 1800s, based on the Shulchan Aruch, which was written in the 1500s. This chapter discusses the medical treatments of the times, some of which may now be discredited. Here, we only address the permissibility of those treatments on Shabbos, not their medical effectiveness. Please consult your own rabbi regarding matters of medical treatment on Shabbos. In case of serious illness or injury, seek medical attention!
91:3 If a person has a minor toothache and isn't in great pain, he may not treat it by rinsing with vinegar or another liquid and then spitting it out. He may, however, rinse and then swallow. (Even so, he should not leave the liquid in his mouth for a long time - Mishnah Brurah 328:101.) He may also dip bread in vinegar and eat it normally. Similarly, one who has discomfort in his throat should not gargle with a liquid; he should swallow it and if it cures his throat as a side effect, so be it.
91:4 If a person has minor stomach pain or scabs on his head, he may not smear them with oil on Shabbos in a place where it is not the practice of healthy people to rub on oil. Since it is only done for medical reasons, his true intentions are obvious. (MB 328:70 seems to permit doing so towards the end of a wound’s duration.)