Red glaze question

[Gabby]

At home I use only commercial glazes in liquid form (typically Amaco but sometimes Laguna) marked non-toxic and food safe, and I brush them on, 3 coats as indicated, then taking them to a kiln at a place whose firing staff I respect. My glazes are marked for cone 5 and pieces always fired at cone 5 as part of a large load of various people's work.

I believe I have read here that it may not actually be prudent, even in these circumstances, to use a red glaze on an eating surface.

Have I misunderstood? 

As a related question, what about a red underglaze, similarly marked, with three coats of clear over it?

Thank you for clarifying.