Kosher eggs: what to check before using them

Eggs from kosher birds (such as chickens) are, in principle, pareve and fit for consumption. However, before using an egg, tradition requires checking that it contains no blood spots in the yolk, since an egg with blood is considered unfit for consumption.

The checking procedure

The procedure is simple: when cracking the egg, visually check the yolk (and sometimes the white) against the light, looking for red spots or marks. It's best to crack each egg into a separate container before adding it to a larger mix, precisely so it can be discarded without ruining the rest of the preparation. If blood is found, the egg is discarded entirely; if the yolk is clean, the egg is fit to use normally.

Why this happens in some eggs

A blood spot usually originates from a ruptured blood vessel during the egg's formation inside the hen, and has nothing to do with whether the egg is fertilized or with any health issue in the bird. It is more common in eggs from older hens, though it can appear in any egg with no predictable pattern, which is why the check is always done, not just "when it looks suspicious."

Other facts about eggs and kashrut

• The shell and white generally don't carry the same risk as the yolk, although custom varies by community: some check both parts with equal care.
• Eggs from non-kosher birds (such as ostrich or certain birds of prey) are also not fit, regardless of the presence of blood, since the underlying issue is the bird's origin, not the blood itself.
• Industrial products containing egg (such as pasta or mayonnaise) generally go through a quality control process that automatically detects eggs with blood via candling, but still require certification to guarantee that control was done under the correct criteria.

Frequently asked questions

Do quail or duck eggs also need to be checked?
Yes, the same criterion applies to eggs from any kosher bird, not just chicken eggs.

Can an egg with a tiny blood spot be saved by removing just that part?
Opinions vary depending on tradition and the size of the spot; some allow removing only the affected point, others require discarding the whole egg. When in doubt, it's best to follow the stricter opinion or consult a rabbi.

Do kosher-certified eggs already come checked from the factory?
It doesn't replace the check at home: certification guarantees the bird's origin and the industrial process, but checking the yolk for blood remains the cook's responsibility, except for industrial products that already went through certified candling.

Related reading

It is one of the simplest habits to incorporate into a daily kosher kitchen: checking each egg as soon as it is cracked, before mixing it with the rest of the ingredients. For other everyday practical steps, see how to set up a kosher kitchen from scratch. And for another pareve food with its own checking rules, see insects in fruits and vegetables.