Many years ago, a friend who was an allergist told us to read the ingredients in foods, to watch out for red and yellow dye. This was about 40 years ago. I’m sure it’s only gotten worse.
That’s interesting about vanillin.
Even “natural” red is a problem. My daughter turned out to be allergic to carmine, which is a natural dye, and it’s made from insect shells.
It took us some months to track it down but I was watching what she was eating and able to make the connection.