> barcodes highlighting allergens and other dangers
Walgreens, CVS, and Walmart already sell homeopathic sugar pills labeled as closely as legally possible to real medication, stored in the same sections, intermingled one box to the next on the same shelf. The lack of information about a product isn't a technology issue; it's a combination of proper information being expensive to produce and more expensive when it keeps you from buying a lower-production-cost alternative.
You see this in all kinds of markets. Say you want to buy a plant grow lamp; you want physical dimensions, power in, and power out. If you're a nerd or using a lot of them you might like the wavelength distribution (_and_ the units used to produce it), the weight, whether it has UV protection, .... That information is ommitted from most Amazon listings and the packaging from most big box stores. Why is it missing? I guarantee the problem isn't that they used a barcode instead of a QR code.