Preservatives in Skincare: Safe limits, natural preservatives, and which ones are best?

European vs. US regulations on preservatives in skincare

The reason for the myth that FDA does not regulate the cosmetics industry comes from generalizing the truth that FDA only bans 14 ingredients from skincare.

What are the banned ingredients?  As of 2011, those ingredients are:

  1. methylene chloride aka DCM (dichloromethane), a carcinogen
  2. chloroform, a carcinogen
  3. Halogenated salicylanilides (4 of these), carcinogenic
  4. bithionol
  5. prohibited cattle material (needs to have BSE/TSE statement, also some restrictions around tallow)
  6. zirconium
  7. vinyl chloride
  8. mercury
  9. trichloroethane (ozone depletor)
  10. hexachlorophene (okay for use in very specific instances with limits on concentration)

By comparison, the EU bans 1328 ingredients from use in skincare.

Approved preservatives in skincare

In addition to those 1328 banned ingredients, EU also has a list of approved preservatives along with their limits for use in skincare products.  The limits (aka concentrations) vary based on the intended use for the product.  Limits are typically lower for leave-on products than they are for rinse off products.

This list is known as List of Preservatives Allowed in Cosmetics Products or perhaps more commonly for people in the industry, Annex V.

This list includes limits for preservatives ranging from each paraben to phenoxyethanol to chlorphenesin and sodium benzoate.  It's a 9 page document (version updated 11Apr2021) with 60 listed ingredients.

There's also another class of preservatives commonly referred to as alternative preservatives.

Alternative preservatives are not found in Annex V.  The reason for this is typically one of one thing:

  1. alternative preservatives are multifunctional ingredients and serve an additional function in the formula... for example, fragrance ingredients like fixatives (which "fix" the fragrance making it linger) that also have antimicrobial properties and perhaps more commonly, ingredients that improve skin feel and increase skin moisturization

For more on alternative preservatives, stay tuned for the next podcast episode.

What preservatives are regulated in skincare in the EU?

Going back to Annex V, even though it includes 60 ingredients, it's possible to take a look at the most commonly used preservatives and their limits according to Annex V.

  1. Parabens.  Parabens are a class of molecules with different side chains hanging off the aromatic ring.  Based on the size of that side chain, parabens are limited to 0.4% as a single paraben or 0.14%.  There's an overall limit of 0.8% total parabens, and certain ones have to be at or less than 0.14%.

    Parabens also have added restrictions in products intended for specific parts of babies' and toddlers' bodies.  Specifically, they're not to be used in products intended for a baby's bottom where babies are prone to develop diaper rash.

    Parabens with a shorter side chain are more active against bacteria and a longer side chain against yeasts and molds.

    When everybody freaked out over parabens in the early 2000s, phenoxyethanol became the preservative of choice for many skincare products.

  2. Phenoxyethanol is limited in leave on products to 1% or less by Annex V.

    While it's quite active against bacteria, it's not as strong an antimicrobial for yeasts and molds, so phenoxyethanol is generally paired with other preservatives or with ingredients that enhance preservative efficacy, which we'll talk about later.

    While phenoxyethanol is a pretty solid preservative from a safety standpoint (Cosmetic Ingredient Review found it's not photosensitizing, very low percent of the population develops an allergy to this preservative, it's non-irritating, etc.), a few years ago, phenoxyethanol came under a great deal of scrutiny. 

    This is because it was being used along with chlorphenesin in products intended for use as a nipple cream by nursing mothers. 

    FDA cited ingestion of this preservative combo as potentially causing vomiting and diarrhea and potentially suppressing the Central Nervous System (CNS). 

    Based on how the FDA warning letter reads and because of the extensive literature around both phenoxyethanol and chlorphenesin, my takeaway was that chlorphenesin was the particular preservative in this formula responsible for these problems. 

    While this is a topic for another day, many cosmetics ingredients have a comprehensive package associated with their safety and efficacy compiled by Cosmetic Ingredient Review, and these preservatives are no exception.

  3. Speaking of chlorphenesin, it's use is limited to 0.3% for leave on products per Annex V.

  4. A few of the other more common preservatives include the formaldehyde formers.  Here's a partial list of those:

    • quaternium-15 (banned in EU since 2017)
    • DMDM hydantoin (0.6% for leave on products)
    • imidazolidinyl urea (0.6% for leave on products)
    • diazolidinyl urea (0.5% for leave on products)
    • sodium hydroxymethlyglycinate (0.5% for leave on)

      The limits for these varies based on how readily the preservative decomposes into formaldehyde.  For DMDM hydantoin it's 0.6%, and this is the same for imidazolidinyl urea as well (0.6%).

      Quaternium-15 was banned for use in cosmetics and skincare in the EU in 2017.  In case you're wondering what other ingredients are banned for use in skincare in the EU, you'll find a link in today's shownotes to Annex II (List of substances prohibited in cosmetics).

      Continuing the list of other common preservatives...

  5. potassium sorbate and its acid form, sorbic acid.  Potassium sorbate's a food grade preservative widely used for its mold killing properties.  While this preservative has a fantastic safety profile, there are people who are allergic to potassium sorbate. 

    Because it is quite gentle, is approved for use in food, and plays well with other ingredients, it's a common choice for use in skincare to boost the antimicrobial capabilities of the product.

  6. benzoic acid and its salt form, sodium benzoate.  Sodium benzoate and benzoic acid are both exceptionally good preservatives for products with a pH under about 5.8 because they exhibit anti-fungicidal properties making them excellent choices to pair with preservatives that are strongly antibacterial in nature.

    These ingredients are limited to 0.5% for leave on products, 1.7% for oral products, and 2.5% for rinse off products, and this is a combo of the two, in other words, the combined concentration cannot exceed those limits.

    A few years ago, there was a great uproar over benzoic acid (or sodium benzoate) and vitamin C in the form of ascorbic acid (unstabilized vitamin C) together creating benzene in products.  This worry came about due to soft drinks.  In low pH environments in the presence of metal catalysts (like perhaps some of the metals present in trace amounts in an aluminum can), benzoic acid can react with ascorbic acid to form benzene.

    Metal chelators prevented this reaction in theory by binding those trace metals.

 And, this leads to the next piece of the conversation...

What are preservative enhancing ingredients?

Preservative enhancing ingredients generally fall into two classes:  chelators and everything else (especially alternative preservatives).

Metal Chelators to improve preservative efficacy

What are chelators?  They're molecules shaped to bind metals.  This includes sodium and minerals like copper, magnesium, zinc, calcium, and iron.  In other words, most chelators are relatively promiscuous and will bind available metals even when they have a higher affinity for one over another. 

What does this have to do with bacteria?

Bacteria require metals for a healthy cell wall, and the chelator sequesters these metals so that the cell wall is more fragile making the cell itself more susceptible to preservatives.

Common chelators used in skincare are:

  1. EDTA, most commonly disodium or tetrasodium EDTA.  This chelator has a robust safety profile and is used for chelation therapy in people (injected intravenously).  The problem with EDTA is that it's widely used and takes a long time to break down in the environment.  EDTA is used in fertilizers, food, pharmaceuticals, and skincare. 

    In foods, it's probably most frequently found in soft drinks where sodium benzoate and citric acid are also ingredients.

  2. Sodium phytate or phytic acid.  This chelator is common in many foods including grains, nuts, chocolate and even tea.  Ruminant animals like goats and cows have an enzyme to digest the phytic acid, the rest of us don't.  This isn't necessarily a problem because phytic acid doesn't get absorbed from the GI tract in humans and other non-ruminant species. It does however mean that any metals bound by phytate don't get absorbed, and phosphorus is commonly bound in phytate when it's present in one of these food sources.

    A topic for a different day is the move to create GMO foods with low phytate levels, my guess is, if it's in these foods, nature put it there for a reason.

    Anyways, phytate's a powerful natural chelator and a great choice for natural preservative enhancement.

    In a future episode, we'll talk about what natural really means.  It doesn't mean, straight from the field into your skincare, it has to be separated from the rest of the plant, and how it's isolated matters in terms of environmental impact and whether residual solvents wind up in your skincare.

  3. Quercetin.  Quercetin is one of those multi-functional ingredients in skincare.  It's a chelator, it's an anti-oxidant, and it also has anti-inflammatory properties.

    While we haven't talked about it on the podcast, there's a dense blog post at Rain Organica discussing the Th1, Th2, and Th17 immune pathways.  The reason I don't use quercetin as a chelator is because of its immune modulating properties. 

    Specifically, some studies show that quercetin's been shown to down regulate the Th2 pathway (reduced IL-4) and upregulate the Th1 pathway (increased IFN-gamma), and this is a potential problem for people with eczema and a few other skin conditions.

    For that reason, Rain Organica uses one of the other chelators mentioned here.

    One more note about quercetin.  Any product containing this ingredient will be yellow in color, think bright sunshine yellow.  If it's not, then quercetin isn't there in significant amounts.  What do I mean by significant?  I'm talking 0.25% or so.

    Early on before I discovered this connection with immunity, I made a bunch of trial formulations with quercetin.  In general, chelators need to be added at a concentration of about 0.1% to 0.25% depending on how strongly chelating they are and how much you want them to add to the anti-bacterial properties of the formula.  Quercetin always, always, always resulted in a yellow product.

  4. Citric acid.  In fact, if you have hard water and need to remove some lime buildup from pots and pans, citric acid's a great (and cheap) choice.  Once again citric acid is natural, please just note, just because it's naturally occurring doesn't mean it's naturally processed or even naturally made.

Stay tuned for the next episode where we discuss alternative preservatives in detail.  In the mean time, check out these additional posts on preservatives and skincare manufacture.

That rounds up some of the major chelators used both in skincare and also in foods.

Next time, we're talking about alternative preservatives.  These are preservatives not yet listed in the EU's Annex V, and the reason for this is often because they're multifunctional.

References

Antimicrobial Chelators and their Mechanism of Action.  Beecroft, Marikka, Shannon (2019) Antimicrobial Chelators and their Mechanism of Action. Doctoral thesis, Durham University.  http://etheses.dur.ac.uk/12933/

Brandy Searcy founder Rain Organica

About the Author

Brandy's a formulation scientist and self-proclaimed health geek who loves hiking, gardening, bird-watching, and body boarding. 

Her struggle with acne during her teens and 20s led to a holistic and healthy approach to skincare, embracing skin as an organ to be loved and cared for rather than a canvas to wage war on. 

Since 2008, she's been developing all-in-one products for a simple routine at home, & Rain Organica started when her backpacking friends asked for a portable skincare routine to keep their skin healthy & happy on and off the trails.

You can try Rain Organica for yourself with The Essentials Kit, a complete skincare routine in just 3 steps.

Brandy's LinkedIn Bio

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