The level of continuously changing complexity for someone like my DD is hard to overstate-- for example, even from manufacturers we trust to label well (we can't just rely on what labels say, even-- not mostly), that can change in a heartbeat.
An example:
When Barilla began test-marketing their egg-containing pastas (the whole grain varieties) about 7-8y ago, my DD knew. How? Well, the label hadn't changed, but she started getting random hive breakouts from some boxes of the regular (non-eggy) pasta. This took us a while to track down, because at that point, they weren't mass-marketing the stuff yet, so we didn't know it existed. We were puzzled, because Barilla had been a completely egg-free facility (and one of the few in N. American markets, btw).
Sure enough, about 9 months into this, they did their roll-out-- and about a year later, finally changed the packaging on their blue-boxed pasta to reflect the shared lines.
She's had similar experiences with any number of products that WERE "safe" from contamination caused by shared production lines... until they weren't. We've also been burned because manufacturers will LIE TO YOU on the phone!!
So you'd better believe we pay VERY close attention to who makes what and in what kind of packaging. We pay close attention to the labeling policies of various companies, (No to Kraft, yes to Keebler, Maybe to General Mills and Kellogg's-- it is VERY VERY complicated).
We buy a LOT of low-processed/unprocessed foods-- because there is no way to match them in terms of safety. BUT-- any processing step that occurs in someone else's kitchen, or around an allergen-- renders safe food unsafe.
Conveying all of that is virtually impossible. Not everyone can understand it.
