Dear Carolyn: My sister-in-law recently discovered, not by talking to a doctor, but by her own decision, that she is allergic to gluten. She cut it out of her diet, and claims that she feels 1,000 percent better. I'm very happy for her, but ...
I do not believe I am allergic to gluten. And I'm getting very resentful of her claiming that everything that's wrong in my life is due to eating it. If I'm tired, it's because I didn't sleep well last night (and again, my insomnia is not due to eating gluten!). If I have the sniffles, it's because I've been around people with colds, not due to my diet. I have tried telling her firmly that I don't have a gluten allergy, and my husband also told her to knock it off, but nothing seems to make a dent in her crusade.
What can I do or say to get her to leave it alone? If it makes a difference, I think it's silly that she self-diagnosed, but I haven't said so to her, and if she really feels better, then, fine.
Resentful? Not just annoyed?
She found a hammer, so everything looks like a nail, and that condition might predate even gluten. If it helps, you're picking up a hammer yourself: an impatience with what you perceive to be dietary fads.
To deal with someone's fixation, your choices are limited to riding it out, avoiding it/her, batting it away with gentle humor -- or taking it seriously. Why not, right? It's just food. Here's a link I found useful (http://hvrd.me/1dYLnTY) discussing gluten and making a good case for going easy on the self-diagnosers.
Another why-not-right? suggestion is to stop telling her "that I don't have a gluten allergy," since that's just fighting one false certainty with another. You haven't been tested either, presumably, so try this tack instead: "I hear you, and realize you feel strongly and want to help. I believe this topic is coming between us, though, more than my diet comes between me and good health. Is there anything I can say to put it to rest for good?"
Might not help, but at least you'll have a "last word" on the record, freeing you to say things like, "This is me walking away from this conversation topic ... ," ideally with a smile and a wave, as you leave the room.