I think Ian has food intolerance intolerance.
Symptoms include increased blood pressure rising uncontrollably and he finds himself muttering and increasingly experiencing feelings of rage in the presence of food intolerances.
In time this can lead to full apoplexy, the results of which can be fatal.
If not for him, possibly for others
I don't think they'll actually die unless I hack out their livers with the butter knife.
It's just that tedious modern day look-at-me-ism.
I'm special. Oh, you're special all right but your liver looks fine. Well, looked. Of course, some people are intolerant to certain foods, beans genuinely give me severe gut cramp and a outcome that's neither natural or normal. So it be, I don't predicate my life by telling everyone about it (the internet excepted, who doesn't like a good poo story). Everyone knows that gluten intolerance is mostly made up, based on a curious mis-interpretation and extrapolation of coeliac disease in which gluten is the actual bad guy. Even if you do react to wheat products, it's more likely to be a reaction to other wheat allergens than gluten.
Yeah, and allergies, the curiously non-specific ones that also weren't diagnosed by a medical professional. I'm allergic to Aspergillus spores. I know this because some evil lady with the benefit of several years in medical school and sporting an appropriate white coat jabbed my arm with several substances and viewed the resulting bright red weal from the mould spores with appropriate disdain. Actually, she was American, so was quite perky.
Oh, I think that one wins! she declared looking at the big red patch that was my lower arm. I ran away before she amputated it for posterity. Even if you are allergic to peanuts, you can't die from sniffing a molecule of peanut released two rooms away, it's not homeopathic.