This situation is non unusual. There are a lot of "Doubting Thomases"

.
Just this morning I was telling my husband that there's someone in his family who still doesn't believe that smoking causes lung cancer, etc. (because she smokes -- we're talking about a 54 year old woman not a kid -- & has to justify her smoking and she's one of the doubting Thom
asses) as regards celiac also; anyway, I likened it to "everyone knows that too much sun can cause cancer
because everyone knows how the sun can burn your skin and everyone knows at least one person who has had biopsies on skin lesions and it was the curable type of skin cancer....that being said I equated skin damage of the sun with lung damage from smoking." But with sun damage is noticable and easily detectable; but lung cancer can ferment and is not visible like the skin is. Smoking is like sun damage but internally.
Anyway, just like it's with smoking-Doubting Thomasses it's the same way with celiac Doubting Thomasses. People aren't satisified unless they can touch, smell, taste or see and hear it or experienced it themselves.
We've learned to avoid the unbelievers as I've noticed (in my opinion) they often are toxic personalities to begin with (uncompassionate, not empathetic, selfish, self-centered, narcissistic, self-righteous, ignoramuses -- gee did I leave anything out?

) .
Sorry I sound this way but the person is my husband's sister and she treats him like do-do and belittles his diet, etc. Unfortunately for her, I think she too has celiac but won't get tested or go gluten-free. She also
really believes that smoking doesn't cause cancer......and that it's all a lie.....