Why Do Eggshells Sometimes Have Weird Bumps and Spots?

According to the United States Department of Agriculture, each American consumed an average of 279 eggs in 2019, making the protein-filled yolks and whites a staple of diets. Low in calories and high in healthy fats, the versatile egg has earned its place on tables.

Grabbing a whole egg from its container, however, can be a stressful proposition. While many eggs sport a smooth and unblemished shell, some rogue eggs present with raised bumps, discoloration, or even spots that materialize once the shell has been cracked.

Why do some eggs look aesthetically off? And are these aberrant eggs safe to consume?

First, a brief primer on how the USDA “grades” eggs. Grade AA eggs are top-shelf (or top-shell) eggs that have thick, firm yolks and whites and unbroken shells. Grade A eggs are essentially the same, though the whites don’t have to be as firm. Grade B eggs loosen the standards for both whites and yolks and the shell might show some staining. These eggs are usually directed toward liquid or dried egg products.

Grade AA or A eggs are no guarantee against discoloration. In addition, there’s no real difference in quality between brown eggs and white eggs. (Their color depends on whether brown-feathered or white-feathered chickens are laying them.)

Let’s examine the most common abnormality in an eggshell—the dark brown spots on a brown egg.

Known as “speckled” eggs, these eggs have spots that are the result of an egg spinning too slowly as it emerges out of a hen’s oviduct, a tube-like organ that processes the yolk and adds the shell and membrane. Some hens—like Welsummers and Cuckoo Marans—are more likely to lay speckled eggs than others. There’s nothing wrong with these eggs and they’re perfectly safe to eat.

Bumps often show up as raised or textured on an eggshell.

They’re most often the result of debris in the oviduct as the shell is being formed. When that happens, calcium will be produced to enclose the debris in the shell. (Sometimes more calcium will be produced for no reason at all.) There’s also no concern here. Eggshell bumps don’t affect the egg itself.

What you want to avoid in a freshly-cracked egg are black spots inside the eggshell. If you see them, it probably means a fungus or bacteria has taken root. It’s best to discard the egg.

Other variables like double yolks and cloudy egg whites are also generally no cause for concern. Some people may even notice a little blood in the yolk, which can appear as a dark brown speck. This is the result of a ruptured blood vessel at the time of ovulation. These eggs are also safe to eat.

The most important variable in egg safety isn’t the presence or absence of spots or bumps. It’s handling and cooking eggs properly. Store-bought eggs should be kept refrigerated and used within three weeks of purchase. Eggs should be cooked until yolks are firm. Hands and surfaces that have been in contact with raw eggs should be washed to reduce the risk of contracting Salmonella, a group of bacteria causing illness.

Otherwise, don't let appearances fool you. Most intact eggs are perfectly safe to eat.

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