When I first had to make drastic changes to my diet, due to my pregnancy, then little nursling at the time, I couldn't have corn, gluten, dairy, soy, oats. So I had to find something else to use as a binder in baking for my gluten free treats. Enter Guar Gum. Corn free and about a third the price of Xanthan gum, it's economical and works just as well. According to Wikipedia,
"Xanthan gum may be derived from a variety of source products that are themselves common allergens, such as corn, wheat, dairy, or soy. As such, persons with known sensitivities or allergies to food products are advised to avoid foods including generic xanthan gum or first determine the source for the xanthan gum before consuming the food."
Guar gum, on the other hand, is made from ground up guar beans. Much more simple and not at risk of triggering a reaction if you're allergic/intolerant to corn, wheat, dairy or soy (depending on what the xanthan gum was derived from). And did I mention it's cheaper? About a third cheaper!