system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do so many people have seafood/shellfish allergies, yet red meat/ poultry allergies are so unheard of?
gpt
Most seafood allergies are a reaction to proteins in the fish or other seafood. We have much more in common with poultry and beef than we do with fish. We share a lot of the same proteins so an allergic reaction to one of those would have killed you because you're made of it. So we are more likely to have a reaction to fish than other meat because we have less in common with it so there are more things you could potentially react to.

Another factor is cooking. Heating breaks down protein that in its uncooked form could trigger a reaction. You wouldn't consider eating a raw burger or chicken breast but sushi is commonplace. This is also why you hear more red meat allergies than poultry. No one wants undercooked chicken but a rare steak is usually preferred.