Is it safe to eat an egg if there's something black inside?

Generally speaking, if the black substance inside an egg is a thin black membrane on the yolk, the egg is usually still edible. However, if the black material inside the egg is caused by spoilage or deterioration, the egg should not be consumed. Detailed explanations are as follows:

If the black substance inside the egg is a thin membrane on the surface of the yolk, it is usually formed by a reaction between iron in the yolk and hydrogen sulfide, producing ferrous sulfide. This black membrane is non-toxic, non-carcinogenic, and does not cause anemia, hair loss, stones, or impair growth and intellectual development. Although this membrane is harmless, it is still recommended to consume such eggs cautiously, as their taste and nutritional value may have been affected.

However, if the black substance inside the egg is due to prolonged storage leading to bacterial invasion, causing the protein to spoil and deteriorate, or if the eggshell has cracks that allow external contaminants to enter the egg, the egg should no longer be eaten. Spoiled eggs may emit a foul odor, and the egg white may turn green or black. Consuming such eggs may cause food poisoning symptoms such as nausea, vomiting, and diarrhea.

When storing eggs, they should be kept in a cool, dry, and well-ventilated place, avoiding high temperatures and humid environments.