I would also ask if he is Celiac or Gluten Free.
My mom is celiac - any gluten and she is very very ill. You'd be amazed what has gluten in it. The biggest issue I had for Thanksgiving last year was gravy, rare to find any packaged anything without gluten in it - they use flour to keep machinery working smoothly in many places that process foods - for my mom that trace gluten used long long ago in the packaging process is enough. For example she can't have steel cut oats, because of flour used in other parts of the process. Even the good companies like Mcwhatever don't work because they farm out packaging and the packagers often use flour elsewhere in their plants.
I'm gluten free just 'cause it make me feel better, and I don't worry about things like that. So, it's 2 different things.