Spotlight On: Phenoxyethanol

Spotlight On: Phenoxyethanol

Recently, a reader asked if phenoxyethanol was the same as ethanol. They are in fact, two distinct molecules. However, they do have some overlapping characteristics and uses. Since I covered ethanol quite extensively HERE, this post will focus primarily on phenoxyethanol.

What is phenoxyethanol?

The cult-classic NARS Sheer Glow foundation uses a phenoxyethanol-based preservative system!

Phenoxyethanol (PE) is an ethylene glycol ether (basically an ethanol molecule attached to a phenol group) that has a viscous or oily texture in its liquid state. In cosmetics, it is most-commonly used as a preservative, appearing in everything from bronzers to liquid foundations (1).

Rather than functioning as an antioxidant-type preservative that reduces the rate of decay, PE functions as an antimicrobial agent, which inhibits or even eliminates “challenging” doses of many variations of Gram-negative and Gram-positive micro-organisms (2). It’s also been shown to be effective against more common strains of bacteria, such as E. coli and Pseudomonas aeruginosa (3).

Is it safe?

If ingested in high concentrations, PE can certainly cause death. However, the scope of this post will be limited to the topical application of standard concentrations (<1.0%) of PE.

In the ethanol post, I discussed whether or not it was significantly metabolized to acetaldehyde in the skin, and if any meaningful amount was systematically absorbed through the skin. Similarly, these two aspects must also be examined for PE. On intact human skin, out of five glycol ethers including ethanol, PE had the highest rate of metabolism to its corresponding acetic acid (ethanol had the lowest rate) (4). If the metabolism pathway of PE is anything like that of ethanol, the next metabolite could be some form of acetaldehyde, which is highly unstable and if not quickly converted to (phenoxy)acetic acid, can generate free radicals.

But before you panic, as we learned in the retinol metabolism post HERE, which also involves the same family of enzymes responsible for PE metabolism, this conversion process occurs below the stratum corneum. Therefore, we need to see what amount of PE is absorbed systematically or basically into the dermis. According to this study that tested absorption of an occluded water-based product containing PE and another antimicrobial, the amount of 2% PE absorbed into porcine skin, which of the tested surfaces is most comparable to human skin in terms of permeability, was only 1.4% after 6 hours and 11.3% after 28 hours (5).

Phenoxyethanol-based antiseptics are safer than ethanol-based ones for babies!

These studies suggest that at <1.0%, the rate of absorption and conversion of PE to potentially harmful intermediates and metabolites, is very low. In fact the exact same product from (5), was tested on premature newborn infants that were <27 weeks old, and the result corresponds to those found in (5). The study demonstrated that, “In contrast to alcohol-based antiseptics, an aqueous solution of … 2-phenoxyethanol does not cause major skin damage… 2-Phenoxyethanol is readily absorbed by the newborn’s skin but apparently undergoes extensive oxidative metabolization to 2-phenoxyacetic acid” (6). The conclusion substantiates the theory that PE has the highest rate of metabolism in skin, while also triggering no measurable damage. If babies can handle it, so can adults.

So how DOES PE compare to ethanol?

While PE metabolism occurs more frequently than ethanol metabolism in the skin, the amount of PE allowed in topical products (<1.0%), is significantly lower than that allowed for ethanol. Therefore, the two balance each other out in this particular aspect. Since the stratum corneum prevents significant absorption of both molecules, any free radicals that are generated will most likely be equal or less than those generated from everyday autoxidation reactions. On a plus side though, due to the phenol group present in PE and consequently its “oily” texture, it evaporates and dries out the skin less severely than ethanol, as witnessed in (6).

Bottom Line

Phenoxyethanol (PE) is a safe and efficacious preservative that is used pervasively throughout the cosmetics industry, second only to parabens. And while I believe that the use of parabens is also safe, if you’re interested in paraben-free products, look for ones that use PE!

What did you guys think of this article?  Let us know down below or on my blog!

Links/References:

  1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3140901/?tool=pmcentrez
  2. http://www.ncbi.nlm.nih.gov/pubmed/7764595
  3. http://www.ncbi.nlm.nih.gov/pubmed/1406341
  4. http://www.ncbi.nlm.nih.gov/pubmed/15551062
  5. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3180697/?tool=pubmed
  6. http://www.ncbi.nlm.nih.gov/pubmed/12183146

About the author: John Su is an established skin care expert and aspiring dermatologist. He also runs a blog, The Triple Helix Liaison, dedicated to providing unbiased, meaningful, and insightful information about skin care. For his full bio, please visit our About Page.

by Nicki Zevola

8 thoughts on “Spotlight On: Phenoxyethanol

  1. John says:

    @Sandra

    Like anything, PE can certainly cause contact dermatitis or an allergic reaction. However, according to the HSDB, http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~baFcml:1, most of the reactions from PE are from improper use, concentration, or just random occurrences.

    And I’m not sure where you’re getting your info, but PE is actually one of less irritating preservatives available on the market. In the full study of this: http://www.ncbi.nlm.nih.gov/pubmed/12423404, which was conducted in 2002, the top allergen was actually nickel sulfate with 16.7%, with formaldehyde at #9 with 8.4%. Phenoxyethanol didn’t even make the top ten. Obviously, the compound and its use hasn’t changed since then, so how could it suddently jump to #2?

    And the only reason that there is an increased amount of allergic reactions from PE, is because PE is being used in more and more products, as I showed in the first cited study. But that doesn’t make PE any more or less toxic.

    Thanks for commenting!

  2. Sandra says:

    What I meant was Euxyl K 400 which is a combination of methyldibromo glutaronitrile and phenoxethanol. You are right that the phenoxethanol component is less of an allergy but the methyldibromo glutaronitrile(MDGN) is what has a high sensitization rate. So most phenoxethanol in the United states is a combination of the two. According to Dr. Baumann’s Cosmetics Dermatology book MDGN has been banned from leave-on and rinse off products in Europe but in United States it is still used in combination with phenoxethanol(Page 140). According to Dr. Baumann (page 142) Euxyl k 400 comes in after Formaldehyde Releasing Preservatives. I am allergic to Euxyl k 400 and was told by my Doctor to avoid phenoxyethanol and MDGN.
    Since everyone wants paraben-free products and companies are replacing them with phenoxethanol or they still use them together it is very hard to find products sometimes.

  3. John says:

    @Sandra,

    Oh, well then that’s a different case. :) As the textbook states, if used in conjunction, the MDGN is usually the culprit, not PE. So your original statement is untrue, since most product available on the US market right now, do not have the two coupled.

    And even when used together, Euxyl K 400, according to that Table you’re referring to (of preservatives that can cause sensitization), which is an estimation by the way, Euxyl K 400 has a sensitization rate of 2.7%, compared to 9.3%-2.8% for FRPs. According to that table, Euxyl K 400 comes in #7, or #3 if you group all the FRPs together. Ironically, parabens are at 0.6% haha! But then again, the alleged issues with parabens aren’t limited to sensitization issues.

    But if you know that you’re allergic to something, avoiding it would be a wise choice!

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  5. Jasmine says:

    Hey John,

    I really enjoyed your posts and scientific references.

    This is a little off topic but I can’t find any information of it.

    Since you compared phenoxyethanol and ethanol, is there any write-ups comparing diols such as glycols to ethanol?

    Thanks in advance.

  6. John Su says:

    @Jasmine

    Thanks for your support!

    I have not written a comparison of ethanol vs glycols, nor do I know of one. In terms of penetration enhancement however, the trend follows as thus:

    The longer the carbon chain of the (linear) glycol, the less effective it is.

    Ethanol is more potent than glycols.

    Keep in mind however, that a few of the smaller glycols–like ethylene glycol are toxic when consumed. Although… ethanol is carcinogenic in itself as well when ingested, though in a different sense.

    Anyways, I hope that helps.

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