This is the theme, because the species, I mean, of the consecrated bread and wine, continue after the Transubstantiation to keep their natural qualities. For example, when we consecrate wine that has a special taste, the consecrated wine will keep this taste, whether it is sweet or not so sweet, and so on.
Also, there were cases where the wine was poisoned. In history, there were situations where someone put poison in the wine before it was consecrated. The poison still had its effect after the wine was consecrated and consumed. As a result, there were priests or bishops who died or suffered health damage.
So it is possible that, in a similar way, when people cannot consume normal wheat bread for physical or health reasons, the Church allows the use of what are called gluten free hosts.
Actually, they look the same as regular hosts. I think they have a slightly different color, but they are still bright in some way, substantially. Therefore, the Church allows them to be used in this case.