Another tidbit I read about the other day, was what if you are allergic to both guar gum and xanthan gum? There were three suggestions. First, you can add one to two teaspoons of powdered gelatin for every cup of flour used. Second, you can use agar flakes or carrageenan using one to two teaspoons for every cup of flour used. They also suggested trying one to two tablespoons of potato flour (not starch) or coconut flour.
I can't speak to the agar flakes, potato flour, or coconut flour, but I have tried the gelatin. It worked for me when I have cooked flatbread and french bread. The gelatin does give the bread elasticity.