Jewish Law

KosherKopy: Unscrambling the Kashrut of Eggs

Are eggs other than chicken eggs kosher?

Eggs are kosher if laid by kosher fowl, and non-kosher if laid by non-kosher fowl. The Shulchan Aruch (YD 86:1) writes that there is no definitive way to determine that an egg is kosher simply by checking its appearance, but there are signs that indicate that an egg is non-kosher. An egg is non-kosher if it is completely round (like a ball) or completely oval (like a football), or if the yolk is not surrounded by the albumen (egg white). A kosher egg will be round like a ball on one side and elongated like an oval on the other, and the albumen will surround the yolk. However, even if an egg has both signs, it is still possible that the egg is not kosher and was laid by a non-kosher bird.

When purchasing eggs from the supermarket, one can be confident that they are chicken eggs because that is what is typically produced in a commercial henhouse. Some people are allergic to chicken eggs and eat duck eggs instead. Duck eggs require kosher certification since one cannot tell from looking at an egg what kind of duck egg it is. Even if the package indicates a particular species of duck, Ashkenazim need to be cautious and only buy duck eggs with kosher certification since Ashkenazic custom is to only eat birds for which they have a direct tradition (mesorah) that they are kosher.


What about buying eggs from a local farmer? Need one be concerned that they may have been laid by a non-kosher bird or from a bird that has no clear mesorah of kashrut?

When purchasing from a farmer, the Shulchan Aruch (YD 86:2) states that the custom is to purchase eggs without questioning the source or inspecting the shape of the eggs, since typically only kosher varieties of birds are raised for their eggs. The Rema, however, adds that this applies only to eggs that have the appearance of regular chicken eggs; if they look different than regular eggs, they should not be bought, even if the farmer insists they are chicken eggs. In recent years, guinea fowl eggs are sometimes sold on roadside stands. Most Ashkenazim do not accept this bird as kosher.


I cracked an egg and saw two yolks inside. May I eat the egg? What if there is no yolk?

Rabbi Chezkiah da Silva (1656–1698) addresses both questions in his monumental work Pri Chadash (86:5). Regarding an egg with two yolks, he writes that this phenomenon is common with kosher eggs and does not present a kashrut problem. With respect to an egg with no yolk, he cites a dispute between rabbinic authorities. One authority (the Maharikash) maintains that an egg with no yolk is not kosher, because the Gemara (Chullin 64a) states that one of the signs of a kosher egg is a yolk surrounded by albumen. If an egg has no yolk, one must therefore assume that it is not kosher. On the other hand, the other authority (the Sha’ar Hashamayim) quotes from a treatise written by Aristotle that when a hen stops laying eggs, the last egg will have no yolk. Therefore, the absence of a yolk is not a kashrut concern. Technically, the Pri Chadash sides with the latter authority, but nonetheless recommends being strict unless the yolk-less egg was already mixed with other eggs.


What do I do if I find a blood spot in an egg I purchased from the supermarket?

Rabbi Moshe Feinstein, zt”l (Iggerot Moshe, YD I:36) maintains that the common custom is to throw away the entire egg if one finds a blood spot in a store-bought egg. Rav Moshe’s opinion, which is the accepted and normative position, is to check every egg for blood spots. The OU requires OU-certified restaurants and caterers to check every egg. However, if an egg with a blood spot was already mixed with other eggs or food and finding the particular egg would be difficult, then one can simply scoop out the blood spot. If the blood spot itself is already mixed in and cannot be removed, it is batel (nullified) and the food may be eaten. This only applies to unfertilized eggs; most commerically sold eggs are unfertilized.


How does a kashrut agency certify liquid eggs? Is there a mashgiach checking every egg to make sure there are no blood spots?

There is no mashgiach checking eggs at factories; however, companies do have candling systems in place for their own purposes to ensure that eggs with blood spots or other abnormalities are not sold to the public. Most eggs with blood spots are detected by electronic sensors during washing and packaging and never reach the market.

On average, each laying hen produces 296 eggs per year. — United Egg Producers

Tosafot (Chullin 64a) write that one may purchase bread kneaded with eggs from a non-Jewish baker who is known to use kosher ingredients. We are not concerned that the eggs may have had blood spots, because holchin achar harov, we follow the majority, and the presence of blood spots in eggs is an uncommon occurrence. Tosafot prove this point from the fact that we eat hard-boiled eggs without checking them for blood spots. Thus, it would seem that when it’s not feasible to check eggs, we rely on the majority.

The Aruch Hashulchan (YD 86:21) asks: if we follow the majority when eating hard-boiled eggs, why is it common practice to check cracked eggs for blood spots? He answers that “following the majority” is not an absolute verification, but only an assumption. We do not rely on assumptions when it is possible to perform an independent verification. However, if one cannot check (such as hard-boiled eggs, or eggs used by a non-Jewish baker), or if one forgot to check, we presume the eggs are kosher.

Are fertilized eggs kosher?

A fertilized egg is kosher provided it does not have a blood spot. While in the past, a blood spot might have signified the beginning of an early-stage chicken embryo (safek sheretz ha’of), today’s commercial methods virtually ensure that this is not the case.

In order for an egg to be fertilized, a rooster must be present. The chicken eggs that we purchase at the supermarket are typically from hens that are raised not for incubation but for human consumption, without a rooster being present. Thus, blood spots in commercially sold eggs are not a sign of a fertilized egg. Instead, they are caused by the rupture of a blood vessel while the egg is forming.


I’ve seen fertilized eggs sold in stores. How can that be?

While most commercially sold eggs are not fertilized, some fertilized eggs are on the market and tend to be labeled as such. They may be found in supermarkets, and some are even certified by kosher agencies. As mentioned above, a fertilized egg is kosher provided it does not have a blood spot. In fact, the Gemara (Beitzah 7a) writes that fertilized eggs are superior in quality to regular eggs. If a fertilized egg has developed to the point that a blood spot appears in any location, the entitle egg becomes forbidden and should be discarded. The OU does not certify fertilized chicken eggs.


A local farmer sells his damaged (cracked) eggs in the form of liquid egg at a reduced price. Am I permitted to buy the liquid eggs from him?

Damaged eggs can come from a kosher chicken or from a chicken that is a treifah (mortally wounded), whch may not be eaten. The Gemara (Chullin 64a) states that one may not sell a whole egg from a treif bird to a non-Jew, because he might sell it to an unsuspecting Jew who will not realize it is non-kosher. What can a Jewish farmer do with eggs that are treif? Must all such eggs be discarded even if the farmer will suffer financial hardship?

There is a simple solution to this problem, based on a long-established custom that Jews do not purchase beaten or cracked eggs from a non-Jew (see Shach, YD 66:9). A Jewish chicken farmer may therefore crack non-kosher eggs and sell them to a non-Jew since there is no concern that a Jew will purchase the cracked eggs.

The US has more than 300 million egg-laying chickens. — American Egg Board

Despite the fact that almost all broken eggs sold by farmers cracked on their own and are not treif, the custom is that a Jew may not purchase cracked eggs so as not to undermine the system that allows selling treif cracked eggs to non-Jews. The Aruch Hashulchan (YD 86:23) writes that this custom of not buying beaten eggs is universal and applies even in communities where Jewish chicken farmers discard non-kosher eggs, since there is always a remote possibility that someone cracked the egg because it was not kosher.


Why are we then allowed to purchase liquid eggs at a supermarket?

Firstly, we are permitted to do so because one should purchase liquid eggs with a hechsher, kosher certification, which ensures that the eggs are from a reliable source. Secondly, when eggs are cracked deliberately in a factory-type setting, there is no reason to suspect that the eggs are coming from an unreliable source.

The OU position is that liquid eggs require kosher certification.


Why do some have the custom to boil at least three eggs in a pot at one time?

When boiling eggs in the shell, there is no way to tell ahead of time if the eggs contain a blood spot. Therefore, there is a custom to boil a minimum of three eggs together so that even if one of the eggs contains a blood spot, that egg would be batel or nullified among the other eggs and the pot would not require kashering.


I have noticed that brown eggs often have brown spots. Are these the same as blood spots?

Approximately 20 percent of brown eggs have protein spots, which are found only in the albumen and give the shell its brown color. These brown spots are not a problem; blood spots in this article refer to spots that are blood red. Some of the pigment excreted by the chicken to color the shell leaks into the egg white and collects in clumps. These colored clumps are at times quite large and have a reddish-brown color. In other cases, the protein spots are just specks that look as if someone sprinkled red glitter into the egg. Rabbi Yisroel Belsky, zt”l, former OU Kosher halachic consultant, ruled that protein spots do not pose a halachic problem.


This article has been adapted from OU Kosher’s Halacha Yomis, a halachah email sent out each weekday and dedicated in the memory of Rabbi Yisroel Belsky, zt”l, former OU Kosher halachic consultant. Special thanks to OU Kosher rabbinic coordinators Rabbi Chaim Loike, Rabbi Eli Gersten and Rabbi Yitzchok Gutterman for their assistance in preparing this article.


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This article was featured in the Summer 2023 issue of Jewish Action.
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