I heard before that if someone washes blood off a service, forensics experts can still determine if blood was there (I think using luminol?). This got me thinking: If the experts' ability to detect blood implies that water couldn't completely wash blood off the service, would that also imply that washing one's hands can't completely remove all blood on one's hands? And if it is forbidden to consume blood, would it be forbidden to eat any food you touch with your hands immediately after washing them?

Since you shouldn't consume blood, does washing your hands remove blood completely from your hands? If not, can your hands still contaminate food in such a scenario? If this would cause you hands to contaminate what it touches, would it be forbidden to eat with your hands immediately after washing blood off them?

  • 1
    Netilat Yadayim is not a wash for hygienical reasons. It is a ritual washing of the hands. Maybe a decent medical scrub is necessary to completely remove all traces of blood, but is that really the point when doing Netilat Yadayim?
    – Shmuel
    Jan 2, 2023 at 14:54
  • Is your concern a barrier to a valid hand washing for bread? Is your question about accidentally eating blood? Is your question about לא תאכלו על הדם? Please edit to clarify
    – Double AA
    Jan 2, 2023 at 15:02
  • @Shmuel My question wasn't clear, so I edited it just now. My concern is that if traces of blood are still on your hand, what if that would make forbidden any food you touch? Does a regular washing of the hands (I shouldn't have used the Netilat Yadayim tag) remove all blood? If not, is a regular handwashing insufficient to clean one's hands, making any food the person touches forbidden?
    – The Editor
    Jan 2, 2023 at 15:59
  • @DoubleAA I apologize for the confusion. My question is about accidentally eating blood, so I edited the question accordingly.
    – The Editor
    Jan 2, 2023 at 16:00
  • 3
    Judaism is not a microscopic religion. It is concerned with whether or not there is visible or tasteable blood, not forensic traces of blood remaining on the hands. The same applies to the kashrus of bugs, for instance, which is why we are not concerned about eating dust mites that are too small to perceive with the unaided eye. NB: If one could see something under optimal conditions (e.g., somebody with excellent vision examining in bright sunlight against a white background), that would be considered halachically visible (Tif'eres Yisra'el, Avoda Zara, Bo'az 2:3; Aruch HaShulchan, YD 83:15).
    – Fred
    Jan 2, 2023 at 19:41


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