Eggshells in a Nutshell: Blue and Green Eggs

What's Up With Blue and Green Eggs?

• Blue eggs are blue because of biliverdin-IX, a pigment that’s produced in cells lining a hen’s oviduct.
• Biliverdin-IX, like protoporphyrin-IX, the pigment in brown eggs, is made from an iron-containing chemical called heme that comes from broken-down red blood cells.
• Biliverdin-IX is added to the hard testa layer of the egg shell during egg formation, so a blue egg is blue all the way through and is blue on the inside of the shell.
• Chickens that lay green eggs incorporate both blue biliverdin-IX and brown protoporphyrin-IX into their eggshells.  Since most or all of the brown pigment is in the bloom, the inside of a green eggshell is blue.
• The hue of green eggs will vary depending on how much brown pigment is present—they can run the gradient from light blue-green to a dark olive.
• While blue eggs are not uncommon in birds (think of robin’s eggs), they are a little unusual in chickens.  All of the chicken breeds that lay blue eggs originated in or contain breeding stock from South America.

Learn about white eggs here!

Learn about brown eggs here!

Blue egg courtesy of Veronica the Easter Egger

A few of the blue/green egg-laying Hipster Hens

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