Yes. Xanthan gum is typically used in gluten free recipes to replace the gluten. It helps the cookies to rise and to have an airy texture. For these cookies I wanted them to be flatter and with a more chewy texture. Omitting the xanthan gum allows these cookies to stay flatter and gives them a denser texture. However, most gluten free flour brands have already added xanthan gum to their mixes.