Thanksgiving dinner tends to have its share of things that you absolutely positively are going to be served whether you like them or not. Rather than falsely declare an allergy to a particular food item (please don’t do that), perhaps you could claim a phobia*. Examples:
Meleagrisphobia is the fear or turkeys. I believe it’s more a phobia of the live guys running around than of a giblet on your plate, but there is little chance that anybody at your table is going to know this.
No problem with the main course? Perhaps you have
potnonomicaphobia, which is a fear of potato products, particularly mashed potatoes. Please note that this is incredibly rare. Most people with a potato-related phobia tend to fear the eyes on old potatoes if a simple Google search is to be believed. Now that I’m thinking about that one, I might have it. I don’t think I can bear to even search to find a term for it. That’s… oh, why did I even find that? Ugh. Moving along.
Are you embracing your inner vampire and trying to avoid garlic? Declare yourself
alliumphobic and be done with it. Or perhaps you’re fine until the dessert course and for whatever reason you cannot bear to eat a slice of pumpkin pie.
Cucurbitophobia will get you out of your predicament far more quickly than a claim of gluten intolerance or sugar aversion ever will.
Perhaps the thing you know that is going to be served that you absolutely cannot swallow is Uncle Kirby’s avowal of love for all things Donald Trump. Just stay home, declare a sudden bout of
Allodoxaphobia (the fear of opinions), and order yourself a nice pizza or something.
*Actually, don’t do this either. All you faux-coulrophobics out there can suck it.