In Kesubos (I believe 60a) it says that you may not drink human blood because of Maris ayin (it can be misconstrued by a observer that you're drinking animal blood).

So what if I have a sign on my theoretical cup of blood saying 'HUMAN BLOOD'. Is there still Maris ayin? Or is this comparable to drinking almond milk where, at least in the Middle Ages, they put almonds around to show any lookers that you're not eating meat and milk together?

1 Answer 1


There is a halacha known as Bal Teshaktzu which prohibits from engaging in any activity that could be viewed as disgusting (see e.g., Avoda Zara 68b). Whether this applies to blood can be derived from SA YD 116:6

It is prohibited to eat food and drinks that a person's soul is disgusted by, such as drinks and food that have vomit or feces mixed with them, and rotten moisture and things like this. It is assur to eat and drink from dirty vessels that a person's soul is disgusted by them, like bathroom vessels and glass vessels that they let blood into.

R Ari Enkin here expands

The Torah considers human dignity to be of primary importance and it is even a factor when deciding halachic matters. [...] One is forbidden to eat any food that most people find disgusting even if one happens to enjoy it. (O.C. Y.D. 116:6, Kaf Hachaim 116:66, Rambam Ma’achalot Assurot 17:29) [...] So too, although eating certain bugs and even drinking urine is essentially permissible, these things should not be done under the principles of Ba’al Teshaktzu. (Tosfot Chullin 66a, Rema Y.D. 13:1, Shach Y.D. 81:3)

Therefore it appears prohibited to drink blood even if it is clear to all this is human blood. Yuk!

  • 1
    mblochs Thanks for the answer. Though is it just anything that's disgusting to most people or is it some something so abhorrent that most people can't understand why anybody could do this? There are many things most people don't like but people still eat. Rare steak, bread with just ketchup, root beer jelly belly, celery flavored soda. What exactly constitutes bal teshaktzu by food? He doesn't really elaborate.
    – Orion
    May 3, 2018 at 3:37
  • This is something that changes with social norms and what is considered acceptable in our day. Indeed R Enkin writes explicitly that The principles of Ba’al Teshaktzu are continually subject to re-evaluation and application based on both personal preferences and social norms.Indeed, we see throughout halachic literature that there have been authorities who would prohibit something under the clause of Ba’al Teshaktzu while other authorities would permit the same things – each based on their own understanding of what is “disgusting”
    – mbloch
    May 3, 2018 at 3:39
  • I would argue that none of your examples (steak, ketchup break, etc.) is disgusting per se. I personally wouldn't try them but it wouldn't disturb me if you would eat them next to me. Not so with blood ! Maybe it is just me though :->
    – mbloch
    May 3, 2018 at 3:40
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    I don't see why you bolded "glass vessels that they let blood into." It has no relevance to drinking blood out of a labeled cup. That line is referring to bloodletting instruments such as needles and blood sacks.
    – robev
    May 3, 2018 at 4:15
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    @robev to show that, if it is disgusting to drink from a glass vessel which previously had blood, then how much more so if it currently has blood in it
    – mbloch
    May 3, 2018 at 4:16

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