Medical use of kaolin

By Josephine Afema, Dale A. Moore, and William M. Sischo


Kaolin (a hydrated aluminum silicate powder) has been used for treating gastrointestinal and other ailments in humans and animals since pre-historic times (Williams and Hillier, 2014).

Pharmacokinetics and potential mechanism of action

Kaolin is a clay molecule with a three-dimensional structural arrangement that forms voids and channels that can trap a wide variety of molecules. Clays decrease the passage time of foods in the digestive tract and thereby increase nutrient digestion. Clays also cause changes in intestinal mucosa (increased villus height to crypt depth ratio) and increase surface area for nutrient digestion (Subramaniam and Kim, 2015). Clay molecules, including kaolin, are reportedly attracted to gastrointestinal mucosa and form a coat; hence prevent toxins and pathogens from being absorbed. The internal surface area of clays (kaolin) is also thought to adsorb bacteria and toxins resulting in transportation and elimination of kaolin-pathogen or kaolin-toxin complex through the gut (Williams and Hillier, 2014).


Kaolin and other clay products are not recommended for treatment of acute diarrhea and treatment with these may result in some unwanted side effects.

Clays are thought to decrease incidence, severity and duration of diarrhea in pigs by increasing the number of Bifidobacteria and Lactobacillus and by reducing Clostridia and Escherichia coli (Subramaniam and Kim, 2015). The space between layers of clay expand to absorb water and cations; hence treated animals have more formed stool. Clays have been documented to alter the microbial population in the gastrointestinal tract. Ion exchange by clays is thought to modify intestinal environmental conditions such as pH and oxidation; hence favoring certain bacteria (Williams and Haydel, 2010).

The most common formulation for kaolin was as Kaopectate. However, kaolin was replaced with attapulgite clay in the 1980s. In 2003 the United States Food and Drug Administration found there was not enough scientific support for the use of attapulgite in treating diarrhea in people and disallowed its use in diarrhea medications (US FDA 2004).

Kaopectate and similar products no longer contain kaolin but may contain bismuth subsalicylate (not to be used in cats). Some veterinary formulations may still contain kaolin. The side effects of clays include constipation, particularly in the young, and decreased absorption of some medications, such as antibiotics. Confusion about what is in the anti-diarrheal products cautions practitioners to read the label for the active ingredients. The primary concern was efficacy of these products, which led to the discouragement of their use in pediatric diarrhea (Thielman and Guerrant 2004).