With me, I think it's the particular shrimp
Several times, in a period 10 to 15 years ago, my lips would swell up like a Ubangi after eating shrimp. Strong antihistamines would knock it back down, so I'm assuming an allergic reaction. I've never had the problem with farmed shrimp from a known source. I'm guessing that the shrimp (who are scavengers) picked up some toxin that I'm sensitive to, in the wild. It's only happened a few times in a relatively short period, and it hasn't resurfaced, so I'm not about to abstain. I did receive all sorts of dire warnings but I guess I just don't take dire that seriously any more either. Oh well...