Yellow 5 is super common (in the US) for things that go inside our bodies. Doritos, Mt Dew, probably Red Bull. When we were kids there was a rumor that it would shrink your dick haha.

Read the ingredients on stuff the next few days and take note of how often you see it. It's probably why they chose it as one of the test substances. It's relatively safe to eat.

What is unknown is how dangerous it is to absorb large amounts into someone's skin.

It's like the illegal weed vape pen issue years ago. People would cut the product with vitamin e to thicken it and also make more money. Vitamin E is safe for human consumption. Turns out its vapor is terrible for lungs. It's quite unsafe for that kind of consumption.