Since prehistoric times, people have been using clay to keep themselves healthy, deal with rashes and make skin beautiful. Clay powder is sold in health food and cosmetics stores for use on the body and in it, as an internal detoxification agent. Its absorbent properties remove impurities and draw out toxins and irritants that cause rashes and blemishes.
Clay is composed of minerals that are very fine, with particles less than two microns (0.002 millimeters) in size that make a sticky mud when combined with liquid. This substance has absorptive properties can draw out impurities. The primary types used in cosmetic and medicinal applications are kaolin, sodium and calcium bentonite, montmorillonite and the substance known as Fuller's earth. They are typically heated or baked, then ground into a very fine powder.
Sodium bentonite clay powder is sold in cosmetics stores for use as a facial mask. The powder is mixed with water to create a paste, and spread on clean skin. When the mask dries, it cracks and is washed off, taking excess oil, toxins and blackheads, the dark material in clogged pores, with it. Clay facials leave the skin feeling soft and smooth. The masks should be used sparingly, however, as clay can be drying and stimulate an overproduction of sebum, making acne problems worse. Most spas use these plus a clay mud bath to soothe and soften skin on the whole body, reportedly a pleasant experience.
Bentonite clay powder is often recommended to help dry and soothe rashes caused by poison ivy and poison oak plants. Urushiol oil that causes the rash is drawn up into the clay and trapped there. The unique absorbent properties of clay cause it to bind to plant oils and encapsulate them. Some users report that clay powder poultices are more effective for poison ivy than commercial preparations. In Africa, tribes in some areas use clay poultices to treat wounds and ulcers that are resistant to healing, with clays that scientists are studying for their antibacterial properties.
Geophagy is the term used for ingesting clay powder or other earth-based substances. Many native cultures in the Americas have used clay to cook foods, and it is not unheard of for people to take earth and clay internally to absorb toxins, act as a laxative and provide much-needed minerals like calcium and iron. Nutritionists have studied this phenomenon, which differs from pica, an eating disorder where the sufferer craves non-edible items. Risks include constipation and a slight rise in blood pressure, as well as a decrease in the effectiveness of certain medications.
Medicinal clay should be as pure as possible if it is going to be ingested. Most people can use topical preparations like masks or poultices without any adverse effects. If a sensitivity to clay powder preparations becomes apparent, their use can easily be discontinued. Cosmetic products may have additives that cause a reaction; a more pure form or a different type of clay may be better tolerated by sensitive skin.