If someone has gum disease and his gums frequently (or always) bleed when he eats, is he restricted to a liquid diet on Shabbos and Yom Tov?
The recently-published sefer Orchos Shabbos suggests that one whould be allowed to eat in this situation, based on Dagul MeRevavah (quoted by Mishnah Berurah 340:17, concerning the consumption of food with words written on it) who rules that a psik reishah d'lo nicha lei (unwanted consequential act) is allowed in a case where the result is damaging (m'kalkel) and the act is done in an unusual manner (k'lachar yad). He cites Rav Nissim Karelitz shlit"a as being lenient regarding this issue.
Perhaps it's a shvus (doesn't want it) d'shvus (netilas neshama isn't done with food) bemakom tzaar or mitzva. Although I don't know if that's the case when he's in pain/not oneg anyway.
There's probably a better answer.