I was just doing some research on this, and found it very odd!
Most sources say that it is highly unlikely to transfer any of the actual oyster shellfish allergens to the oyster's shell and then to the inside of the egg. Especially since what the shell is made up of is calcium carbonate. The person should have only had a reaction if they came into contact/are fleshy bits or juices of the oyster.
Also, I read that commercial egg production places probably use oyster shell as a supplement also (or they probably feed a "complete" layer feed which would more than likely have that in it). I wonder if that person has a problem with store eggs also, Or maybe it was a coincidence and she came into contact with seafood elsewhere.
I have never heard of this being a problem before ever, so I f ind it quite interesting!
Lots of people in who live by the coast in Australia use the big chalky calcium rich cuttlebone from cuttlefish - which are kinda like squid/octopus - the cuttlebone wash up on the beach and are easy to find. The birds love them! Might not be as easy to find inland thou!
No definitely not. Haha :) thanks for sharing!
It could have been that the hen scratched around in the shell then touched the egg. I have pastured chickens so I had never used shell before. She got sick the very week I used it. Shes so allergic, she cant even go to the beach because seaweed might touch her! Its a rare case, but better to beware first. Now I ask all my customers and friends.