Food Poisoning—But the Shell Color Is Not the Reason
Green-shelled chicken eggs can look unusual enough to make some shoppers hesitate. Their shells may be pale mint, blue-green, olive, or dark mossy green, leading to online claims that they are “medicinal,” genetically modified, chemically treated, or even dangerous.
The scientifically accurate answer is much less dramatic: a naturally green shell does not make an egg poisonous. There is no established evidence that green-shelled chicken eggs cause a special disease that white or brown eggs do not.
However, eating any raw, undercooked, cracked, contaminated, or poorly stored chicken egg can cause foodborne illness. In other words, green-shelled eggs can cause food poisoning under unsafe conditions—but their color is not the cause.
Why Are Some Chicken Eggs Green?
Eggshell color is mainly determined by the hen’s genetics. Different chicken breeds deposit different pigments while the shell forms in the reproductive tract.
Research has identified biliverdin as one of the pigments responsible for blue or blue-green coloring. Olive-green shells generally result from a combination of blue-green biliverdin and reddish-brown protoporphyrin pigments.
This coloration is naturally incorporated into or deposited on the calcium-carbonate shell. It is not evidence that dye, chemicals, medicine, or spoiled material has entered the edible part of the egg.
Breeds such as Araucanas and several related or crossbred chickens are known for laying eggs that range from blue to green. The U.S. Department of Agriculture explains that shell color is determined by the hen’s breed and does not create a meaningful nutritional difference. Claims that naturally colored eggs automatically contain less cholesterol or are dramatically healthier than ordinary eggs have not been proven.
