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Controversial Ingredients: Setting the Record Straight

By: Ada Polla and Anne Pouillot
Posted: January 30, 2012, from the February 2012 issue of Skin Inc. magazine.
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page 8 of 17

Aluminum salts should probably be replaced. They can be irritating, they should not be applied to broken skin, and their use should be stopped immediately in case of itching.

Instead of aluminum salts, natural active ingredients, such as triethyl citrate, alum stone (potassium alum) and perlite, can be used as alternatives. Citric acid from the juices of cherry or currant inhibits the enzymes responsible for the decomposition of sweat. Alum stone neutralizes odor and regulates perspiration without preventing the natural breathing of the skin. Perlite, a mineral extracted from volcanic rock, acts as a sponge to absorb moisture without preventing the natural breathing of the skin.23

Propylene glycol

Propylene glycol, also known as 1,2-propanediol, is an organic alcohol. It attracts water, reduces flaking and restores the skin’s suppleness. Propylene glycol is also used to help stabilize formulas and is a solvent that dissolves natural extracts.

It has a bad reputation because consumers associate propylene glycol with brake and hydraulic fluids, and antifreeze, not understanding that there are different grades of this product. Moreover, its effect on the skin is drying, because it partially dissolves the intercellular cement of the stratum corneum and decreases corneocyte cohesion, hence increasing TEWL.24 Indeed, high concentrations of propylene glycol in water kept in contact with human skin can cause irritation.25 No reaction was observed when tested in the open air on human subjects. One report indicates rare eczematous skin reactions and, even more rarely, an allergic reaction following exposure to propylene glycol.26

Propylene glycol should probably be replaced. In the United States, it is listed as GRAS (generally recognized as safe) for use in food and pharmaceuticals in the U.S. Food and Drug Administration (FDA) document US—Pharmacopoeia (Ref21CFR). However, given its use in other industries, consumers are confused and are afraid of propylene glycol. Furthermore, because of its drying effect, it is best to limit its use, especially in the case of a difficult dissolution of an active ingredient or the use of hydroglycolic plant extracts.

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