The proof for me is in my clear skin.
While I haven't had an allergy test, the proof for me is in my clear skin. But I must warn you, there is one drawback: The white sponge is very easily stained. (Which is probably one of the reasons the brand decided to color its sponges.) Luckily, it's my flawless foundation that I'm more concerned about, not the stains on my sponge. So for me, it's dye-free all the way.