1) Extracting blood or pus is included under the category of ''Mefarek'' - ''extracting'' - and is a derivative (''Toldah'') of ''Threshing'' - ''Dosh''. 2) Blood which has already come out of the gum may not be swallowed, even on a weekday. 3) If one has to dress a bleeding wound with something that was not intended for that purpose, one should wash away the blood first, so as to avoid transgressing the prohibition of ''Dyeing''. However, if washing it is not practical or will cause a delay that risks further injury, one may use any material to dress the unwashed wound. Anything which is specifically intended for use as a dressing, such as gauze, or a bandage, may be applied to an unwashed wound under all circumstances.

1) One of the 39 Avot Melachot (prototype prohibited activity) is shearing - ''Gozez'' - an animal for its wool. Any activity which involves removing from the body of a person or an animal, something which grows on the body, such as skin, hair or nails, is prohibited as a derivative (Toldah) of ''Shearing''. 2) In order for an act of ''shearing'' to be Biblically prohibited, it has to have been performed with a tool usually used for that purpose, for example, nail scissors or tweezers. Pulling off a nail with one's hand isn't the usual way of accomplishing that task, therefore the act is only prohibited Rabbinically. In cases where the majority of the nail has become detached AND there is physical pain involved, the Rabbis did not prohibit removing the nail in an unusual manner (i.e. with one's hands). The Shulchan Aruch however doesn't differentiate between pieces of skin and nails. So if the majority of a strip of skin becomes detached, and it's painful, one may detach it with one's hands (See Mishna Berurah 328:95).

ציצין שהן כמין רצועות דקות שפירשו מעור האצבע סביב הצפורן אסור להסירן בין בכלי בין ביד בין בשינים וצפורן שנפרש רובו וקרוב להנתק ומצערו מותר להסירו ביד אבל לא בכלי ואם לא פירש רובו אסור להסירו אפילו ביד

1) Since marinating or pickling a food item alters its state, it's considered similar to the act of cooking, and is therefore Rabbinically prohibited on Shabbat (Mishneh Torah: Shabbat: 22:10). Based on this, the Shulchan Aruch 321:3 rules that it's prohibited to perform acts on Shabbat which resemble pickling, like salting four or five radishes at a time. Therefore, since putting a liquid into vinegar, is, in a sense, ''pickling'' the liquid, one may not do this on Shabbat. It's allowed, however, to add water to vinegar in order to weaken its strength (see Mishna Berurah 321:15).