You crack an egg and there is a spot of blood in it. Modern egg farming genuinely changed the facts underlying this question — but it did not settle it, and the honest answer is that poskim divide.
Blood in an egg means any red spot, clot or red mark. Where it is forbidden, it forbids the whole egg — which also rules out using that egg in cakes, in mayonnaise, spread on bread, or in anything else.
What the prohibition rests on
Two layers, and the difference matters for everything below.
- From the Torah: blood found on the knot from which the chick forms.
- From the Sages: any blood found on a fertilised egg. A fertilised egg here means one a hen brooded on, in which a drop of blood formed as the beginning of the chick.
Why modern farming reopened it
Almost all eggs today come from layer houses where the hens are kept for eggs and no roosters are present. The birds lay by artificial heat, and the eggs are not fertilised.
On that basis a number of poskim permit such an egg where blood is found — discard the blood, and the egg may be used. Their reasoning is that the prohibition attaches to an egg from which a chick could develop, and this blood came from a different cause altogether: sapna me'ar'a, the heat of the ground the hen sat on. That is not an invention for modern conditions — the Gemara itself permits an egg whose blood came from the ground's heat.
This position is held by several Acharonim and by Rav Ovadia Yosef, and it is the basis on which commercially marketed eggs from caged layer flocks are treated leniently.
Why others are not persuaded
Three distinct objections, and they do not stand or fall together.
1. The market is not uniform. A minority of eggs on the market do come from hens kept with roosters. If those have blood, they are forbidden. Since that forbidden minority is present, one cannot permit an egg found with blood simply on the strength of what most eggs are.
2. Sapna me'ar'a may be narrower than it looks. Many hold that the permission for blood from the ground's heat applies only where such eggs have spoiled and are unfit to eat. If so, it does not transfer to an ordinary edible egg at all.
3. The prohibition may have nothing to do with chicks. This is the sharpest point. Tosfos records that the prohibition on blood in eggs is a decree lest people come to permit the blood of a bird — not because of the chick's blood. On that reading, whether the flock had roosters is simply irrelevant, because fertilisation was never what the decree was about. And so any blood found in an egg would be forbidden.
There is also a practical objection about the flocks themselves: chicks are sexed while very small, when male and female are hard to tell apart, and the work is done fast and in volume. Roosters do get into laying houses. The claim that a given house has none is a claim about a process, not an observation.
The custom, and what to do in practice
The practice recorded is to forbid — blood in the yolk or in the white alike — other than in pressing circumstances.
Where circumstances are pressing, the practice is narrower and worth knowing precisely:
- Touch cotton wool to the blood. If it is absorbed and the yolk did not burst, it is permitted.
- Or lift the blood out with tweezers or a pin. Again, if the yolk did not burst, permitted in pressing circumstances.
Which practice your household follows is a question for your rav, and a real one — this is not a case where one answer has quietly won.
How to check
Lechatchila, every egg is checked before it is opened into anything else.
The rule that follows from that is the one most worth adopting: where you are using several eggs, open each one into a separate vessel and check it there, before it joins the food or the other eggs. One unchecked egg cracked straight into a bowl of six can carry all of them, and nothing about the finished batter will tell you.
Eggs found inside a slaughtered hen
A separate case with a more lenient outcome. An egg found inside a hen after shechita, with a speck of blood in it, is permitted — discard the blood on it. This holds even where the egg came from a flock in which hens and roosters were kept together.
Are eggs meat, dairy or pareve?
A laid egg from a kosher bird is pareve, and may be eaten with meat or with dairy.
An egg found inside the hen after shechita, not yet laid, is graded by how finished it is:
| State of the egg | Status |
|---|---|
| Complete — white and yolk both formed | A finished egg; permitted with milk, even though still attached by sinews. Some are stringent while it is attached |
| Shell formed, even only the white membrane | Does not have the status of meat |
| Unfinished — only the yolk present | Has the status of meat; may not be cooked or eaten with milk |
Where the yolk-only egg is eaten on its own, one may eat dairy afterwards. And some record a custom from the Acharonim not to eat any egg found inside a bird together with milk, even where the outer shell had hardened — though bedieved, an egg with even the white membrane formed is permitted with milk. See waiting between meat and dairy.
Eggs that are forbidden outright
- An egg of a non-kosher bird.
- An egg from a bird that was neveilah or treifah — and an egg found inside a bird that died of itself.
- An egg in which the chick has begun to form.
- An egg forced out of a live hen before it was finished, while still attached by sinews — this is ever min ha-chai. Where it was not attached by sinews, it is permitted.
Anything you actually find in an egg is a question for your rav.