I don't have allergies. Or maybe I do. Recently, I noticed a correlation between eating shrimp and getting a wild and itchy rash on my arms and neck. I haven't been tested, but I think it's best that I not eat shrimp. When offered a plate of shrimp appetizers, I am trying to say, "No, thank you," because I don't want to introduce the subject of itchy rashes at a perfectly lovely cocktail party. My "no, thank you" is usually well-received, as it should be. But occasionally it isn't.
I think we all need to learn when to say it and when to hear it without comment. Let's bring back "no, thank you" and follow it with a full stop.