Article by: Perry Romanowski

We received this question here at Chemists Corner central and thought it would be a good one to write an article about.

“Why do the raw material suppliers recommend the combination of presevatives versus using them alone…..for ex: why do the manufacturers recommend a combination of sodium benzoate and potassium sorbate rather than using them individually….

Why you put preservatives in cosmetics

With all the bad press about chemicals used to preserve cosmetics you might wonder why companies don’t just stop using preservatives.  Well, the reason is that cosmetics that contain preservatives are safer than ones that don’t contain preservatives.  This is because disease-causing microorganisms can multiply at exponential rates in cosmetics if there are no chemicals in there to stop them.

And if the consumer is putting a dollop of microbe laden skin lotion on their body, they are bound to contract a disease.  It is just not smart to use unpreserved cosmetics.

The other reason to include preservatives is that when microbes grow in your cosmetic product they can produce foul smelling odors and strange colors.  Consumers just aesthetically do not want to use bacterial contaminated products.  It’s a bit like the same reason people don’t want to eat moldy bread.

What do preservatives do

Cosmetic formulas have all the key factors needed for microbial growth including water, nutrients, and energy.  At a suitable pH and temperature, it will be like a microbial cocktail party.  Preservatives stop growth by killing cells and spores (usually by disrupting cell membranes) or by making the system hostile to growth.  See this article for more about cosmetic preservatives.

Why you need multiple preservatives

So that brings us to the question that started it all, why use multiple cosmetic preservatives?  Basically it’s because some single preservatives do not kill a big enough range of microorganisms.  As a cosmetic formulator you need to ensure that your preservative system will kill any bacterial, mold, or fungi that the formula might encounter.  Since you don’t know what will be encountered you have to plan for every possibility (or at least as many as you can).

There are some preservatives that are able to kill a wide range of microbes (e.g. Alcohol, Parabens, Formaldehyde donors).  That is why these ingredients are so popular with formulators.  Other ingredients like Sodium Benzoate or Potassium Sorbate are only effective against certain types of microbes.  They are more active against yeasts and molds but have a lower activity against bacteria.    One way to compensate for the ineffectiveness of one compound is to include another compound that has the ability to kill other organisms.  By combining preservatives, you increase the spectrum of microbes that your formula can withstand.

Of course, if you used parabens and formaldehyde donors you could be more confident in the effectiveness of your preservative system.  However, for marketing reasons these compounds must be avoided.  It makes your job as a cosmetic formulator a bit harder.

14 comments

  1. Humala

    Hello guys, i am making tonic for hair. Its compounds are ascorbic acid, tea extract and water.
    Can you please suggest me a suitable preservative which will not damage or harm hair skin and the tonic?
    In addition, may i know how much is the maximum percentage for using potassium sorbate as preservative for skin?
    Thank you.

    1. Perry Romanowski

      It really depends on your formula.

  2. Pradeep thakran

    Hello Perry,

    Also can you advise if my anhydrous product require a preservative?

    One Lip Balm formula is as below:
    Oil Phase @ 100% Grams
    Coconut Oil @ 25% 25 gr.
    Kokum Butter @ 10% 10 gr.
    Cocoa Butter @ 5% 5 gr.
    Almond Oil @ 10% 10 gr.
    Rice Bran Oil @ 20% 20 gr.
    Avocado Oil @ 5% 5 gr.
    Castor Oil @ 5% 5 gr.
    Beeswax @ 20% 20 gr.

    Value Items @ 5% Drops/GM
    Rose E/O @ 0.1% 4
    Saffron E/O @ 0.1 % 4
    Soya Lecithin @ 0.2% 0.3 gr.
    Vitamin E @ 0.1% 0.5 gr.
    Rose Extract @ 2% 2 gr.
    Rose Petals Powder @ 1% 1 gr.
    Pink Color 5
    Phenoxyethanol @ 0.5% 0.5

    1. Cynthia Scott

      My understanding is that unless there is water or hydrophilic ingredients (water loving ingredients – such as honey, hydrosols… – some extracts are water based so that if your rose extract is water based then it qualifies) an anhydrous formula does NOT require a preservative.

      1. Perry Romanowski

        Even if you have an anhydrous formula, you should use a preservative. Consumers can contaminate products with water which could lead to dangerous microbial growth.

  3. Pradeep thakran

    I am formulating Natural range of cosmetics so wants to avoid synthetic preservatives. Can you advise on below combinations, which is best as overall complete preservative system:
    1. Benzyl alcohol(50%)+ Potassium Sorbate(40%)+ Sodium Benzoate(10%)
    2. Benzyl alcohol(25%)+Phenoxyethanol(25%)+ Potassium Sorbate(40%)+ Sodium Benzoate(10%)
    3. Phenoxyethanol(50%)+ Potassium Sorbate(40%)+ Sodium Benzoate(10%)

    Also i am using 0.1% Vitamin-C in my formulation. Will this be problem with sodium benzoate?

    your early response will be highly appreciated.

    Thanks!

    1. Perry Romanowski

      Any of those could work depending on the system you are formulating. You haven’t given enough information (eg. the whole formula) to provide an answer. I would just test them all to see which one works the best.

      1. Pradeep thakran

        Dear Perry,

        I want to go for one standard perservatives system for my lotions, creams, Mask, which has water in the formula etc.

        One of the formula is as below:
        Oils @ 20% 200gm
        Emulsifier & Thickener @ 7%
        E-Wax @ 5% 50 gr.
        Beeswax @ 1% 10 gr.
        Cetyl alcohol @ 0.3% 3 gr.
        Stearic Acid @ 0.7% 7 gr.

        Water Stage @ 68%
        Water @ 50% +10% loss 550 gr.
        Glycerin @ 3% 30 gr.
        Sorbitol @ 1% 10 gr.
        Aloe Vera Gel @ 6.5% 65 gr.
        Honey @ 0.5% 10 gr.
        Sodium Lactate @ 2% 20 gr.
        Extracts @ 5% Grams
        Aloe Vera Extract @1% 10 gr.
        Rose Extract@1% 10 gr.
        Licorice Extract@1% 10 gr.
        Carrot Root Extract@1% 10 gr.
        Honey Extract@1% 10 gr.

        Value Items @ 2% Grams
        Vitamin-E @ 0.1% 1 gr.
        Vitamin-A @ 0.1% 1 gr.
        Vitamin-C @ 0.1% 1 gr
        Vitamin-B5 @ 0.7% 7 gr.
        Zinc Oxide @ 0.5% 5 gr.
        Citric Acid @ 0.5% 5 gr.
        Milk Powder @ 1% 10 gr.

        Preservatives @ 1% Grams
        Phenoxyethanol @0.5% 5 gr.
        Potassium Sorbate@0.4% 4 gr.
        Sodium Benzoate@0.1% 1 gr.

        Essential Oils @ 1% Grams
        Rose@0.6% 6 gr.
        Geranium@0.4% 4 gr.

        Please let know what is best natural preservative combination i can use. Also is Vitamin-C(Ascorbic Acid) a problem here as i am using sodium benzoate. Also what is approx. shelf life of this formula.

  4. Cleo

    Hi,

    I am an aromatherapist, and I am in the process of developing products for the general public, subject to a suitable and effective preservative. Like many consumers I am interested in avoiding or limiting unnecessary exposure to synthetic ingredients. However, as a provider of products I have a responsibility to ensure they are safe. People recoil at the thoughts of ‘preservative’. I think they forget what preservatives are preserving them from. Thank you for your clear and honest information. If we had been searching the last hundred years for effective preservatives, people would be all too aware of the short shelf life and harmful things that can thrive in a product, and they would now be grateful for the discovery of something which eliminates those problems and hazards. The benefit of using an effective preservative with a very low toxicity outweighs the risks posed by unpreserved products, given what can accumulate in them.

    My question is about sodium benzoate. I sell a range of hydrolats distilled from organically grown plants. Since these are intended for a variety of uses including drinking (in small quantities), alcohol is not a suitable option. Sodium benzoate dissolves easily in water, therefore it would be well dispersed. Would you think it would be effective enough, and also safe enough to consume?

    With thanks,
    Cleo

    1. Perry Romanowski

      Sodium benzoate is used as a food preservative however, I’m not well versed enough in the rest of the ingredients in your formula to give you advice.

      1. Maresa Walsh

        The hydrolats are herbal waters distilled using only the plant in question, such as lavender, roman chamomile, tea tree. Without sodium benzoate, they are safe to use and consume, but they have a short shelf life. As far as I know, sodium benzoate may present a problem when combined with potassium benzoate and vitamin C/ascorbic acid. This combination is not present in hydrolats. Are there other harmful interactions you are aware of with sodium benzoate?

        With thanks,
        Cleo

        1. Perry Romanowski

          It’s doubtful there would be a problem with sodium benzoate that isn’t also a problem with potassium benzoate. When dispersed in a water solution they will essentially be the same ion. I’m not familiar with any other harmful interactions with sodium benzoate. It is not a great preservative for cosmetics however.

  5. Tanya Robertson

    I’m looking to create a line of lipsticks and glosses. What is the best way to find a cosmetic chemist to assist me with this. Please help. Thank you in advance.

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