I had a conversation with a person the other day that has an allergy to white shelled eggs, but not brown. From what little I think I know about chickens and eggs, the only difference between white eggs and brown is the shell color. I was intrigued, so I did a little "research".
White eggs often come from hens with white ear lobes.
Brown eggs often come from hens with red ear lobes - like Kathy and Eleanore.
The beautiful blue eggs come from Araucana hens. (Must be to make up for the butter face - "That's a good looking hen, but her face...")
After gathering some information I have formed this hypothesis:
The white eggs this person has consumed have mostly been from the grocery store.
The brown eggs this person has consumed have mostly been from free range or backyard chickens.
Backyard birds, often red ear-lobed, have a different diet than white ear-lobed factory (battery) hens, therefore - WAIT FOR IT - the allergy originates with the chicken feed!