Can one place ice on cold sore on Shabbos?
Cold sores are treated with medication, therefore placing ice on them if the sore is outside of the mouth would be an issue, because one may come to use a medication. If however the sore is inside the mouth, the person may such on ice, as it looks like a normal thing that is done, and doesn’t appear as being to heal. However if the person is in a lot of pain, even if it isn’t enough for him to be bedridden from it, he may ask a gentile to do administer a medication that is only forbidden m’drabonon.
O:CH 328-1, M:B 3, 83,