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.
Blue egg courtesy of Veronica the Easter Egger

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