Xanthan gum is a natural polysaccharide produced from the fermentation of glucose. It is used extensively in the cosmetics industry for its thickening abilities and emulsifying qualities. It is also used in the food industry in gluten-free recipes and as a thickener in salad dressings and sauces.  It can be sprinkled into shampoo or other surfactant based products to thicken.  Use sparingly, stir well and add slowly to avoid clumping.