I'm severely allergic to shellfish.I was told I almost died when I was given a lobster tail,but I was too young to remember it myself in the here and now.Apparently,from what I was told,my throat swelled shut?

After I learned some religions forbid shellfish,I've always wondered if at some point in the past,it came to be that it was forbidden because somebody had a severe allergy,and it wasn't understood properly.Think of it.A person in a jewish tribe suddenly develops hives all over their body,repeatedly throws up,and suddenly can't breathe.I'm not sure how advanced they would be in old testament times,or if they could conceive what was happening.For the allergic reaction itself,one of the religious leaders might conclude the person was possessed by a demon if no connection was made between the allergic reaction itself,and eating shellfish.If a connection was made to consuming shellfish,and a horrific reaction eventually,the person who noted the reaction might not have any way of explaining it.They also would have no way of knowing if the allergic reaction was a one time deal,or if everybody might be in danger of having some kind of spell from shellfish.They might not have a concept of how to explain why it isn't to be consumed,so the only way they know to express it is to claim that shellfish is 'unclean'.

Then I considered pork and Trichinosis,and I thought maybe it was similar reasons.

I did read a page later on that gave me the vague impression that some foods are kosher due to the animals nature,and in a vague way I got the impression that perhaps it is/was believed that only animals that had desirable characteristics were fit to eat,perhaps that the food consumed gives the person aspects of it's personality?I'm quite vague on that,and perhaps I read to much into it?This is the page I read: http://www.torah.org/learning/olas-shabbos/5763/shemini.html But I still wonder about my original theory.

(I'm not picking on jewish dietary laws,they're just the only one where much has been written about dietary laws.None of this is meant to offend anybody.)