Arrowroot powder is a starch derived from a South American plant and is used as a thickener in recipes. This powder is used in the same way cornstarch is, though there are some differences between the two starches. Arrowroot is a root starch that acts as a thickener.Arrowroot powder is light, soft and absorbent. It is used in making body powders. When applied topically, it helps dry blemishes, rashes or other sores, or wounds.Arrowroot Is a Healthier Alternative to Cornstarch. Sometimes called a starch and other times a powder, arrowroot is more desirable as a thickener than often-genetically engineered (GE) flour, cornstarch or rice. “Cornstarch is a powdery substance made from (surprise!) corn and is used to thicken gravies and sauces.