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The use of medicinal clay in folk medicine goes back to prehistoric times. Indigenous peoples around the world still use clay widely, which is related to geophagy. The first recorded use of medicinal clay goes back to ancient Mesopotamia.
A wide variety of clays are used for medicinal purposes—primarily for external applications, such as the clay baths in health spas (mud therapy). Among the clays most commonly used are kaolin and the smectite clays such as bentonite, montmorillonite, and Fuller's earth.
Ancient Egypt and Mesopotamia
The first recorded use of medicinal clay is on Mesopotamian clay tablets around 2500 B.C. Also, ancient Egyptians used clay. The Pharaohs’ physicians used the material as anti-inflammatory agents and antiseptics. It was used as a preservative for making mummies and is also reported that Cleopatra used clays to preserve her complexion.
The Ebers Papyrus of about 1550 BC (but containing the tradition going back many centuries earlier) is an important medical text from ancient Egypt. It describes the use of ochre for a wide variety of complaints, including for intestinal problems, as well as for various eye complaints.[unreliable source?]
This was a clay used in Classical Antiquity. It was mined on the island of Lemnos. Its use continued until the 19th century, as it was still listed in an important pharmacopoeia in 1848 (the deposits may have been exhausted by then).
if rubbed under the eyes, it moderates pain and watering from the same, and prevents the flow from the lachrymal ducts. In cases of haemorrhage it should be administered with vinegar. It is used against complaints of the spleen and kidneys, copious menstruation, also against poisons, and wounds caused by serpents.
Lemnian clay was shaped into tablets, or little cakes, and then distinctive seals were stamped into them, giving rise to its name terra sigillata—Latin for 'sealed earth'. Dioscorides also commented upon the use of terra sigillata.
Another physician famous in antiquity, Galen, recorded numerous cases of the internal and external uses of this clay in his treatise on clay therapy.
Galen... used as one of his means for curing injuries, festering wounds, and inflammations terra sigillata, a medicinal red clay compressed into round cakes and stamped with the image of the goddess Diana. This clay, which came from the island of Lemnos, was known throughout the classical world.
Other clays used in classical times
The other types of clay that were famous in antiquity were as follows.
- Terra chia, Terra cymolia (Cimolean earth): these were both white earths and considered of great value.
- Samian earth: Pliny in c. 50 AD (Nat. Hist.) details two distinct varieties, colyrium - an eye salve, and aster, which was used as a soap as well as in medicines.
- Terra sigillata strigoniensis (Strigian earth, derived from Silesia) - this clay, yellow in colour, appears to have been famous later in medieval times.
All the above seem to have been bentonitic clays.
- The earth which did not stain the hands was known as rubrica.
In medieval Persia, Avicenna (980-1037 CE), the 'Prince of Doctors', wrote about clay therapy in his numerous treatises.
- the terra sigillata,
- Egyptian earth,
- Samian earth,
- earth of Chios,
- Cimolean earth or pure clay (cimolite), soft earth, called al-hurr, green in color like verdigris, is smoked together with almond bark to serve as food when it will turn red and assume a good flavor; it is but rarely eaten without being smoked—also called 'Argentiera',
- earth of vines called ampelitis (Pliny XXXV, 56) or pharmakitis from Seleucia in Syria,
- Armenian earth (also known as the Armenian bole), salutary in cases of bubonic plague, being administered both externally and internally,
- earth of Nishapur.
A French naturalist Pierre Belon (1517–1564) was interested in investigating the mystery of the Lemnian clay. In 1543, he visited Constantinople where, after making enquiries, he encountered 18 types of different products marketed as Lemnian Earth (he was concerned about possible counterfeits).
He then made a special journey to Lemnos, where he continued his investigation, and tried to find the source of the clay. He discovered that it was extracted only once a year (on 6 August) under the supervision of Christian monks and Turkish officials.
Preparation of clay
Clay gathered from its original source deposit is refined and processed in various ways by manufacturers. This can include heating or baking the clay, since the raw clay tends to contain a variety of micro-organisms.[notes 2]
Too much processing, likewise, may reduce the clay's therapeutic potential. In particular, Mascolo et al. studied 'pharmaceutical grade clay' versus 'the natural and the commercial herbalist clay', and found an appreciable depletion of trace elements in the pharmaceutical grade clay. On the other hand, certain clays are typically heated or cooked before use.[notes 3]
Medicinal clay is typically available in health food stores as a dry powder, or in jars in its liquid hydrated state – which is convenient for internal use. For external use, the clay may be added to the bath, or prepared in wet packs or poultices for application to specific parts of the body.
Often, warm packs are prepared; the heat opens up the pores of the skin, and helps the interaction of the clay with the body.[notes 4]
In the European health spas, the clay is prepared for use in a multitude of ways – depending on the traditions of a particular spa; typically it is mixed with peat and matured in special pools for a few months or even up to two years.
"The majority of spas … use artificial ponds where the natural ("virgin") clay is mixed with mineral, thermo-mineral, or sea water that issues in the vicinity of the spas or inside the spa buildings."
Clays contain large amounts of trace minerals. It is common to see as many as 75 different trace minerals in Montmorillonite clays. Specific trace minerals that various clays possess vary very widely. Also, the amount of any particular trace mineral in any specific clay varies a lot among clays from different locations. For example, the amount of iron in various bentonite clays can vary from well below 1%, and up to 10%.
Many types of skin conditions have been treated by the application of medicinal clay. Montmorillonite has shown its effectiveness in this area. It has also been used as a base ingredient for tissue engineering. Clay is used in many dermatological over-the-counter remedies, such as in acne treatments (this information may not be mentioned on the label specifically).
There are many over the counter remedies for internal use that contained clay before discontinuation. Examples include Kaopectate (Upjohn), Rheaban (Leeming Div., Pfizer), and Diar-Aid (Thompson Medical Co.). The labels on all of these showed the active ingredient to be Attapulgite, each tablet containing 600 (or 750 mg) of this component along with inert materials or adjuvants. However, since April 2003, attapulgite medication was discontinued due to lack of evidence according to the U.S. Foods and Drugs Administration.
Numerous medicines also use Kaolinite clay, which has long been a traditional remedy to soothe an upset stomach. Also, Kaolin is or has been used as the active substance in liquid anti-diarrhea medicines such as Kaomagma. Such medicines were changed away from aluminium substances due to a scare over Alzheimer's disease, but have since changed back to compounds containing aluminum as they are most effective.
Heavy metal chelation
It has been found that prolonged exposure to bentonite in humans can actually have harmful effects.
Use by the NASA space program
The effects of weightlessness on human body were studied by NASA in the 1960s. Experiments demonstrated that weightlessness leads to a rapid bone depletion, so various remedies were sought to counter that. A number of pharmaceutical companies were asked to develop calcium supplements, but apparently none of them were as effective as clay. The special clay that was used in this case was Terramin, a reddish clay found in California. Benjamin Ershoff of the California Polytechnic Institute demonstrated that the consumption of clay counters the effects of weightlessness. He reported that "the calcium in clay ...is absorbed more efficiently ... [clay] contains some factor or factors other than calcium which promotes improved calcium utilization and/or bone formation." He added, "Little or no benefit was noted when calcium alone was added to the diet."
Side effects of ingestion
Substances discontinued such as kaolin and attapulgite were formerly considered gastric demulcents and diarrhea medication, until official studies by the USFDA disproved these views. Clays are classified as excipients and their main side-effects are that of neutral excipients, which is to impair and slow down absorption of antibiotics, hormones and heart medication amongst others by coating the digestive tract  and this slowed down absorption can lead to increased toxicity of some medication (e.g. citrate salts) which can become toxic if not metabolized quickly enough, which is one contraindication of attapulgite. Usual mild side-effects are nausea, slowed down absorption of nutrients from food (in excess dosage of medicinal clay) and constipation.
Common medicinal clays
- Bentonite-type clay has been used to treat infections, indigestion, and other medical problems by both applying wet clay topically to the skin as a poultice, and by ingesting it. Bentonite has been prescribed as a bulk laxative, and it is also used as a base for many dermatologic formulas. Dermatologically, it is used as part of a treatment for pruritus. Bentonite itself is not classified as a carcinogen, but some bentonite may contain variable amounts of respirable crystalline silica, a human carcinogen.
- Montmorillonite is the main constituent of bentonite.
- Palygorskite or attapulgite is a very absorbent clay, somewhat similar to bentonite. When used in medicine, it physically binds to acids and toxic substances in the stomach and digestive tract. For this reason, it has been used in several anti-diarrheal medications, but studies of such have since been rejected by the U.S. Food and Drug Administration as insufficient.
- Kaolin is not as absorbent as most clays used medicinally (it has a low shrink-swell capacity). Also, it has a low cation exchange capacity. This clay is also known as 'white cosmetic clay'. Clay, in the form of kaolin, was a common ingredient in western medicines such as Kaopectate, Rolaids and Maalox, but is no longer present in them nor in similar preparations, as it is considered ineffective by the USFDA.
- For further discussion see:
- "Soil, including kaolinitic and montmorillonitic clays, contains considerable amounts of organic material, including many live microorganisms."
- An example of this is the medieval 'Argentiera' clay, mentioned in this article.
- "Hot application is recommended in geotherapy, pelotherapy or paramuds in beauty therapy..."
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