The Shulchan Aruch rules that one must wash one’s hands before dipping food into certain liquids.[1] These seven liquids are: wine,[2] honey, olive oil, milk, dew, blood, and water.[3] While it is somewhat common to dip foods into most of these liquids (i.e. cookies and milk, apples and honey), it is unclear why blood is included in this list considering that it is forbidden to consume blood in the first place![4]
A number of answers have been offered to explain this oddity. Some suggest that blood is included in this list for the sake of those who need to consume blood for health reasons.[5] Another answer offered is that the Shulchan Aruch is referring to a situation where a food is accidentally dipped in blood. For example, if a carrot is dipped (or falls) into blood, only the part with blood on it would be forbidden to eat. The rest of the carrot, however, may be eaten. Nevertheless, one would still be required to wash one's hands before eating the clean side of the carrot.[6]
According to Torah law, it is permitted to drink one's own blood. Doing so, however, is forbidden according to rabbinic law. The rabbis prohibited consuming any blood that has separated from one’s body due to maarit ayin, the concern that onlookers might suspect that one is consuming a forbidden food.[7] As such, it is forbidden to lick or suck on a bleeding cut.[8] So too, one whose blood dripped onto food would be required to cut away any parts of the food with blood on it. The rest of the food may then be eaten. On the other hand, one who is bleeding in one's mouth is permitted to ingest the blood emerging from the wound. This is because it is not noticeable that such blood has separated from the body. So too, no one can see that one is ingesting the blood.[9]
Blood that has changed color, or is otherwise unrecognizable, may be consumed if it can be assumed that an onlooker would not suspect that one is consuming blood.[10] As such, it might just be that it was for this reason that the Shulchan Aruch ruled that one must wash one’s hands before eating foods that came into contact with blood. On a related note, the Talmud teaches that one should not slice bread or meat in one’s hands. Not only is doing so unsafe, but, if one indeed cuts oneself, any blood that gushes out from the wound “would ruin the food!”[11]
Finally, it is noted that a number of authorities permit one to consume fish blood should one enjoy doing so.[12] As such, one who enjoys dipping foods into fish blood must wash one’s hands before doing so. It might just be, therefore, that the Shulchan Aruch was referring to fish blood when it included “blood” in the list of liquids that require one to wash one’s hands before dipping foods into.
The reason that it is forbidden to consume blood is because blood is considered the life source of an animal. So too, according to kabbala, consuming blood can cause one to become animalistic in nature. It is also explained that consuming blood would be improper as blood was something that earned us atonement when it was offered on the altar of the Beit Hamikdash.[13]
[1] OC 158:4.
[2] Whenever wine is mentioned in halachic literature, it includes grape juice as well.
[3] This includes any drink whose primary ingredient is water such as tea, coffee, and soda. Kitzur Shulchan Aruch 40:21.
[4] Mishna Berura 158:17; Be'er Heitev 158:10.
[5] Mishna Berura 158:17.
[6] Rema, OC 158:4.
[7] YD 66:10.
[8] Darkei Teshuva 66:68.See also Kaf Hachaim, YD 66:47.
[9] YD 66:10.
[10] Nezirat Shimshon 158.
[11] Berachot 8b.
[12] YD 66:10.
[13] Ramban, Vayikra 7:26.