If I poked myself with a knife and possibly got blood on it; does it have to be kashered.


2 Answers 2



(I need to provide sources, I know.)

There's talk about whether a slaugher knife remains fully kosher, but that discussion is always about whether the blood heat of the animal (did you know that the duck as the highest internal temperature of kosher animals in the literature?) "cooks" the blood into the knife. Human blood heat is certainly less than "yas soledes bo" (the temperature at which your hand would get uncomfortable), so the blood doesn't get cooked or otherwise driven in. Just wash the knife really clean, and you're fine.

(Weirdly enough, human blood is only a rabbinic prohibition, not Biblical. But the reason the knife is okay here is because it didn't absorb.)

  • I thought it was a goose.
    – Isaac Moses
    Commented Apr 26, 2010 at 1:42
  • I'm thinking of R' Shlomo Zalman Auerbach's determination of "yad soledes bo" temperature, where he works with duck blood temperature as still not yad soledes bo, and reckons that a duck could get to about 113 F. I could be mistaken; where's the discussion about goose?
    – Shalom
    Commented Apr 26, 2010 at 2:43
  • I guess I remembered wrong.
    – Isaac Moses
    Commented Apr 26, 2010 at 12:59

The consumption of human presents a number of halachic problems/prohibitions but they are not related to kashrus strictly speaking.

Human blood is prohibited because of Maris Ayin, it is not even strictly speaking a "Rabbinic prohibition". As such there is, I believe, no concept of tam k'ikkar (the taste is like the forbidden substance). As such while it is prohibited to eat bread which has blood from one's gums on it, such blood would not impart a forbidden taste to utensils. (Shulchan Aruch, Yoreh Deah 66:10)

  • Good point. But even if the question was about a non-kosher animal, e.g. "I accidentally cut my pet humpback whale [has a lower temperature than humans]", the knife doesn't absorb the blood and would still be okay if cleaned well.
    – Shalom
    Commented Apr 26, 2010 at 14:16
  • But what about human flesh?
    – Dov F
    Commented Jul 25, 2012 at 16:36

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .