Husband again. When I met the Wife, I had a bit of a learning curve when it came to living alongside someone with a severe allergy. Personally, I do not have any allergies and lived life under the "see food" diet - I saw and ate. I also grew up in an era where severe food allergies were not as commonplace, so it was never really something that was front-of-mind. Throughout the dating and early marriage stages, there were some lessons that were learnt that I thought might be useful if one has a (potential) life partner with an allergy.
Her Allergy is Your Allergy
In choosing to, at first date, then marry someone with a severe allergy, I've in essence adopted that allergy as my own. Admittedly, I was never a huge seafood connoisseur before and since then, I haven't consumed seafood for a very long time. In our earlier years, I used to refer to it as my "second-hand allergy". With the possibility of giving my wife a reaction if we kiss, enjoying that piece of sushi or shrimp cocktail is not worth the risk (or the alternative of being relegated to the couch!). Even when ordering at a restaurant, it's much easier to tell the server that I have an allergy as well, rather than the long(er) explanation of, "I don't have an allergy, but I don't want give my wife a reaction so please treat my food as if I do."
You Have to be Her Advocate
As the Wife can attest, it can be tiresome to self-advocate as it relates to allergies. Whether it's talking to restaurant staff, hosts at a dinner party, or scouting out a potluck table, your partner can't do all the work.
Please Don't Joke About It
For someone that does try to keep things light, I can't recall being guilty of this myself, but rather when we were with someone else. Before we got married, we went out with some people where someone talked about how funny it would to slip me some seafood just before our wedding day (see above as to why). While they didn't actually do it, I do question why under any other circumstance it would be "funny" to joke about potentially ruining someone's wedding day and/or risk poisoning the bride. Really??
In this day and age where it's generally inappropriate to joke about someone's health conditions or disabilities (amongst other things), allergies should be no different.
And while I'm on the topic - if someone tells you they have a seafood (or any) allergy, please don't respond by telling that person they don't know what they're missing and recalling that time you went to such-and-such a place and had the best, fresh seafood in your life.
It Can Be More Encompassing Than a Meal
One thing worth keeping in mind is that it can affect your social calendar or travel plans. Your friends really want to go for a certain cuisine? Maybe we'll hang out another time. Cocktail party where they're serving seafood finger food and shaking hands? Might have to call it a night. Travelling out of town? Seafood might be more popular and readily available than at home, so you might need to have some backup plans or choose another destination. Going to a buffet? High risk of cross-contamination so you might need to make other plans (probably for the best as my waistline is thanking me on that one).
Random Lessons
A few other anecdotes along the way. Back in my university days, I worked at a fast food establishment, and saw what happens to a stray french fry when it sits in a deep fryer for a few hours. When we first got together, I thought hot deep fryer oil would kill any seafood proteins and mitigate the risk of a reaction. News Flash: that doesn't happen.
A few years back, I was listening to talk radio where the topic was about a waiter who served a customer seafood, despite being told about the allergy. It seemed the host and some of the callers (not affiliated with the linked article) weren't taking the topic too seriously, with some callers even questioning how a patron could not know the taste of seafood. My response would be as someone who grew up in rural Alberta, I was taught that antifreeze has a sweet taste and you should ensure your pets aren't around if you're working with it; otherwise, they will consume it and it's toxic. Would I personally know the taste of antifreeze? Of course not, it's toxic to humans as well, and I'd rather not make that discovery the hard way. For the same reason, someone who is deathly allergic to seafood likely wouldn't know its taste until it may be too late.
Conclusion
I should conclude this by saying I don't feel I've missed out by having to give up seafood, nor do I regret doing so. Whether it's a life partner, a child, or a roommate, there might be situations where it would be necessary to make lifestyle changes to accommodate that person.