So I don't know if we have any dieticians on here, but I feel like the chances are good we have someone who knows their stuff.
My mum is allergic to cheese. Or intolerant - I'm not clear on whether allergies only encompass anaphylaxis, but it makes her vomit so violently that on more than one occasion she's had to be hospitalised for dehydration and put on a drip. Travelling in France with someone whom cheese could literally kill is...well, interesting. Please forgive my clan, La Chaise - the rest of us eat enough cheese to make up for it.
Anyway, she's fine with any other dairy products - milk, yoghurt, ice cream, etc. So we've theorised that perhaps it's the rennet she's allergic to. Does that make any sense? She's not allergic to any other animal proteins as far as we can tell. Or is it the casein?
Her other allergies are wasp stings (bees are fine, apparently) and erythromycin (an antibiotic - I share that one). Her brother is allergic to, of all things, bananas - anaphylaxis there. I swear this isn't "fussy foody" stuff - it's put-you-in-the-hospital stuff. I've only been given erythromycin once (and I have no idea why they did, as they usually give it to people who're allergic to penicillin, which I'm not) and next time I'll just die of tonsillitis - it was wretched. My brother doesn't have any allergies I'm aware of - though he has a weird invulnerability against nettle stings - and nor does my maternal grandmother. For some reason my mum and her brother just have these weirdly specific allergies.
Although come to think of it, I don't eat bananas anymore, because I love them but they give me tummy ache. That might be relevant.
Dieticians and cheese-makers, go!