Xanthan Gum is one of the few ingredients I could find that started with X. It's made by fermenting corn syrup with a particular bacteria. OK, I'm sorry, it already sounds like sci-fi. It is used as a thickening ingredient and to suspend particles like herbs in the dressing. Now that I have learned this little tidbit, it makes total sense why some bottled salad dressing look so unnatural to me.
Xanthan gum is used in gluten free baking to improve the stability and texture of baked goods. It is a corn product, so there is always that GMO thing to think about. I bought a bag of this scary stuff like two years ago when I was going to test for a GF book. It's weird and crazy sticky stuff if you spill it and accidentally get it wet I think it is still in my pantry...and I have no intentions of pulling it out. I may have to donate it. Hee hee.
Oh and then there is Xylitol. It is a sugar substitute for diabetics and is believed to help with inner ear infections. It is found in many toothpastes as it has some anti-cavity properties. While there are natural forms of Xylitol, most of the stuff in the stores goes through lots of processing and even hydrogenation. It's also toxic to dogs. I'm not so crazy about the X ingredients. That's all I've got for X! I promise to be more inspired for Y and Z!