Bentonite, also referred to as Montmorillonite, is one of the most effective and powerful healing clays used by indigenous cultures since before recorded history because of its healing benefits.
Bentonite is sedimentary clay from volcanic ash. It is an effective and cleansing clay if used externally as a face mask, in the bath or externally as a clay poultice. Internally it can be added to water or glazed upon food to help those with sensitive palates.
To use as a face mask — Mix 1-2 teaspoons with enough water to make a paste and apply to the skin. Leave to work for 10-15 minutes and rinse with clean warm water and pat the skin dry. Add a couple of drops of tea tree oil for added benefit for clearing spots.
To use in the bath — Add 2-3 tablespoons to the bath and mix thoroughly.
To use internally — It is generally advisable to start with 1 tablespoon of bentonite clay daily, mixed with a small amount of juice then gradually increase the dosage to no more than 4 tablespoons daily.
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http://en.wikipedia.org/wiki/Medicinal_clay