Do water free sugar or salt scrubs need a preservative?

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There appears to be some confusion about whether or not an anhydrous SUGAR/SALT scrub needs a preservative.  I have brought a fair few products to market that do not contain water.  These range from lip balms, face and body balms to anhydrous sugar and salt scrubs and none of these have required a conventional  preservative or a preservative efficacy test (PET) under EU law.  I have also looked at the market and noticed many anhydrous products on the market that do not contain preservatives – these are from both big and small cosmetic companies. I have visited and consulted with a number of microbiologists that perform PETs that do not push micro testing or preservatives in many anhydrous products.  So when I read on some sites quoting microbiologists that an unpreserved anhydrous sugar/salt scrub is UNSAFE I was surprised and mystified!

This post is going to look at the reasoning behind PETs, touch on current EU legislation and practical considerations when deciding whether a preservative in your anhydrous sugar or salt scrub is necessary or even effective. What are the arguments for using a preservative? I understand the rationale behind why a preservative should be used on a product that could come into contact with moisture.  The idea is that when you are in the shower and you use a sugar scrub, water is likely to get into the container.  Water along with sources of energy and heat are the conditions for bacteria, yeast and mould to grow, so it would make sense that a preservative is needed.  These scientists argue that the preservative should be a traditional water soluble one so that when water gets into the scrub it will cross over into the water quotient and protect it. 

No mention is made by the same scientists about other things within a product which could help protect it. But is it practical and does it actually make the product any safer than if it simply contained no preservative?  In my view, and in the view of many highly qualified safety assessors (including clinical pharmacologists who consider the entire safety profile of the product, not just its microbiology aspect) it does not.

So how do formulators and safety assessors determine whether a product needs a preservative or a preservative efficacy test?  What governs the decision making process? How do the professionals determine whether an aqueous and non-aqueous product is safe?

The EU has some very specific guidelines and legislation around cosmetics products set out in the EU Cosmetics Directive. This directive is based and informed by the knowledge of chemists, microbiologists and other specialists in the field who make up the Scientific Committee for cosmetic products. In the EU it is compulsory to have a safety assessment which will also include preservatives efficacy testing if indicated. 

The ‘suitably qualified’ safety assessor has to justify every decision they make in a Cosmetic Product Safety Report and their guidance specifically refers to different International Organisation of Standards (ISO) for different areas of testing.  The ISO are internationally recognised minimum standards which set out guidelines for good manufacturing practice, guidelines for performing preservative efficacy tests  for different pathogens and risk assessments for identifying low risk products that do not need preservative efficacy testing (ISO 92621).   They will also look to COLIPA: Guideline for Microbiological Quality Management (MQM). Similarly in the U.S a chemist will use or adapt the same ISO’s and also use the United States Pharmacopoeia.  The idea of having this standardise basic guideline is to make trade between countries more, let us say, standard.  If everyone has the same basic commonly accepted testing methods then there should be no need for additional testing which could halt or delay trade.

EU Legislation

When deciding on whether a preservative is needed the chemist/safety assessor will (a) look at the composition of the product (b) look how it is likely to be used under normal conditions and (c) use industry guidance such as ISO, USP and EU Directives and guidance. They will also look at things like duration of contact of the product on the skin and concomitantly exposure rates.  Altogether there are 10 different aspects to the report but they are not all relevant here. Let us look at this in relation to the above:

  • What is the composition of an anhydrous salt and sugar scrub and its physical characteristics?

A salt/sugar scrub will contain high amounts of salt or sugar (>60% probably), will have oils, butters and maybe waxes.  May or may not contain an emulsifier and will probably have some kind of fragrance/essential oil blend. We can assume that each ingredient is 99-100% pure and the toxicological profile for each ingredient is sound based on the INCI and certificate of analysis.

  • How it is likely to be used.

EU legislation states that;

‘Cosmetic products should be safe under normal or reasonably foreseeable conditions of use. In particular, a risk benefit reasoning should not justify a risk to human health.’

So what does this mean?  When determining how to safety assess the product the assessor has to consider how it is supposed to be used.  Normal use would be that as a scrub it is going to be used in the shower or bath on damp skin, rubbed on the skin and then showered/washed off within a matter of minutes.  Is it reasonable to expect that some water is going to get in there? Yes, I would say so – water will drip from the hands into the container.  Is it reasonable for the container to get completely flooded with water?  Probably not; it would not be pleasant, generally unsightly and most of the salt/sugar would dissolve.  So under normal and reasonable foreseeable use the product is going to only be in contact with the skin for a short while and will only be subject to  a small amount of water.  Working from these assumptions we could probably say that our salt or sugar solution left over by the drips of water is going to create a self-preserving product.  

Does it need a preservative? With regards to whether a product needs a preservative efficacy test, the safety assessor may look at different levels of guidance to support their justification.  In the EU they will probably look to the Guideline for Microbiological Quality Management (MQM) and ISO 29621:2010 standard “Cosmetics -- Microbiology -- Guidelines for the risk assessment and identification of microbiologically low-risk products’’.  The former is specific to the EU and the latter is an international standard that came into effect in 2010.

ISO 29621 – This document (used in most countries) helps identify low risk products that do not require preservative efficacy testing.  Such things as pH of the product, active water (water available for microbes to survive), high alcohol content (>20%), pour temperature and the use of different materials which will inhibit (or be a hurdle to ) the growth of microorganisms are all taken into account (either in combination or separately) in deciding whether a cosmetic is low or high risk and concomitantly whether a PET is necessary. 

What is significant to my argument is the ‘water activity’ of the product.  The rationale is summed up as follows;

“The water activity (aw) describes the amount of biologically available water within cosmetic formulations and is determined by comparing the vapour pressure of the formula containing water with the vapour pressure of pure water. Water activity may be reduced by the use of water binding substances, such as salts, polyols, protein hydrolysates, amino acids and hydrocolloids . Different classes of microorganisms have different tolerance to low water activity; bacteria generally have higher water requirements than yeasts, and yeasts higher requirements than molds. Gram-negative bacteria show more susceptibility to low aw values than gram-positive. Sorbitol and glycerol, in concentrations of around 20% w/w, are most commonly used to reduce water activity’’ ( KABARA, J.J. and ORTH, D.S., Principles for product preservation in preservative-free and self preserving cosmetics and drugs, Marcel Dekker, New York, pp. 1-14, 1997)

iso-29621

iso-29621

So, if we follow on from above, an anhydrous sugar/salt scrub will generally start off with low water activity as it does not contain water (or only trace amounts). If it does come into contact with water, which is very likely, what will be created is a salt or sugar solution which is likely to create an environment non-conducive to microbial growth. 

How can we know that the solution that is created is strong enough to inhibit growth?   The answer is that we cannot know for certain as we cannot predict exactly how much water will go in there –  But we can operate under the presumption that the end user will use the product sensibly and how it is supposed to be used ‘under normal, reasonably foreseeable conditions of use’ 

Similarly, we cannot be certain the amount of water will not be too much of a burden on a conventionally preserved product. Below is a summary of low risk products that do NOT require preservative efficacy testing.  Taken from ISO 29621: 2010.   Source: ISO 29621: 2010

Duration of contact and exposure rates

Let’s consider that the product is contaminated (usually by mould  - as that needs the least amount of water to grow) A scrub is not likely to be on the skin for very long as it will be washed off almost instantly by the shower or bath.  As such the risk is minimum because the exposure is minimum.   But let’s face it, if it is mouldy then it is not likely to be used!  (yes and I do know you cannot see bacteria) Things to consider when using a preservative: Let’s say that you have an anhydrous sugar scrub that contains a preservative.   There should only be enough preservative in the product to protect the product for the duration of the life of the product under normal use.  This means that it is not reasonable to expect that it will be used other than how it is marketed.  So we know it will not be used as a facial moisturiser or a body cream as that is certainly not reasonable or normal when it is marketed as a body scrub.  Let's also hope people follow the directions. Preservatives are potent chemicals which have a specific safe use rate – It is dangerous to use more than is recommended and you cannot use more to cover any extra water coming into the container.  A safety assessor will not pass your product if there is more than the legal safe limit.  If the scrub is used in the shower or bath and if water gets into the container will it have enough preservative to cover the extra water?  Will it be more or less effective than sugar or salt?  Again, that is uncertain.  The hidden preservative There is also an argument that the product that contains ‘parfum’ have a hidden preservative.  These antimicrobial agents are often marketed as fragrance materials or skin conditioning agents (phenethyl  alcohol, sodium anisate, p-anisic acid, sodium levulinate etc).  Officially they do not fall under the EU list for acceptable preservatives in the directive so are not classified as preservatives but have antimicrobial activity which makes them a preservative (in the real sense).  However, to say ‘it has a hidden preservative’ simply because it has the word ‘parfum’ is not an argument as it is not categorically proven that this is the case. If a sugar scrub needs a preservative then why not a lip or skin balm? If we are to believe that an anhydrous sugar/salt scrub needs a preservative then what about other anhydrous products that could come into contact with moisture?  If we follow the pro-preservative-in-scrubs logic then we have to consider that all products that come into contact with moisture - regardless of whether they are in the shower or not -  need a preservative.  Lipsticks and lip balms are in contact with lips and saliva which contain micro-organisms that can multiply. Often we have high levels of humidity in the atmosphere yet, a preservative in other anhydrous products are not considered to be a high risk.  Why is this? What makes these products different?   To me, the fact that there is a risk of moisture means that the same should apply, yet it does not: at least not in the minds of some experts. So to summarise;

  1. The sugar or salt solution is probably going to be enough to counter any bacteria, yeast and mould if only a limited amount of water gets into the container (under normal and reasonable use) but will probably not cover much more water than that.

  2. Similarly, if you use a preservative it will only cover a tiny bit of water getting into the pot and will not protect the product if too much water gets in there.

  3. The current advice given in ISO 29621 is that anhydrous products are low risk and it does not distinguish between those in contact with water and those that are not.

  4. Whether there is a need for a preservative is dependent on many factors and it is very formula dependent. Does it contain water? Does it have high levels of glycols, salt or sugar? What type of container is it in? Are there botanical's or anything else that can be additional sources of pathogens? Are there any essential oils that can contribute to preservation? Essentially we can not give a blanket answer to the question of preservatives with out asking these sorts of questions.

FINAL WORD Ultimately it is your business and you need to do what is right for you so if you want to use a preservative  in this type of product, go ahead and use one. I suppose the extra help couldn't do any harm.  My only advice would be to research independently, look at journals and other publications and follow the advice from people that are objective. FINAL, FINAL WORD Below is a selection of products on the market, some from large well established companies and some from lesser well known enterprises.  Some have no traditional preservatives and some have oil soluble preservatives,  (which goes against the advice to use a water soluble one).   And, for the sake of argument – you cannot class anything that creates a ‘hurdle’ as a preservative!!!

  • The Body Shop Spa Wisdom Africa Ximenia & Salt Scrub

Glycerin (Humectant), Sodium Chloride (Viscosity Modifier), Beeswax (Emulsifier/Emollient), Cetearyl Alcohol (Emulsifier), Disodium Lauryl Sulfosuccinate (Surfactant), Sodium Cocoyl Isethionate (Surfactant), Zea Mays (Corn) Starch (Absorbent/Chelating Agent), Butyrospermum Parkii (Shea Butter) (Skin-Conditioning Agent/Emollient), Fragrance (Fragrance), Cocamidopropyl Betaine (Surfactant), Hydrogenated Castor Oil (Emollient), Water (Solvent/Diluent), Ximenia Americana Seed Oil (Emollient), Hexyl Cinnamal (Fragrance Ingredient), Butylphenyl Methylpropional (Fragrance Ingredient), Limonene (Fragrance Ingredient), Benzyl Salicylate (Fragrance Ingredient), Alpha-Isomethyl Ionone (Fragrance Ingredient), Titanium Dioxide (Colour) PRESERVATIVE: NONE.  There is a high amount of glycerin, lots of detergents, there could be a 'hidden' preservative but that can not be a given. For the sake of this arguement there is no traditional preservative.

  • REN Moroccan Rose Otto Sugar Body Polish

Saccharum Officinarum (Sugar), Prunus Amygdalus Dulcis (Sweet Almond) Oil, Olea Europaea (Olive) Fruit Oil, Glyceryl Stearate, Carthamus Tinctorius (Safflower) Seed Oil, Parfum* (Fragrance), Rosa Damascena Flower Oil, Cymbopogon Martini Oil, Pelargonium Graveolens Flower Oil, Geraniol, Linalool, Citronellol, Ilex Paraguariensis (Paraguay Tea) Leaf Extract, Cola Acuminata (Kola Nut) Seed Extract, Coco Glucoside, Tocopherol PRESERVATIVE: NONE

  • Lush Rub Rub Rub

Fine Sea Salt (Fine Sea Salt), Sodium Laureth Sulfate (Sodium Laureth Sulfate), Fresh Organic Lemon Juice (Citrus limonum), Water (Aqua), Sodium Cocoamphoacetate (Sodium Cocoamphoacetate), Jasmine Flower Infusion (Jasminum officinale), Mimosa Absolute (Acacia decurrens), Orange Flower Absolute (Citrus aurantium amara), Jasmine Absolute (Jasminum grandiflorum), Lemon Oil (Citrus limonum), Lactic Acid (Lactic Acid), Lauryl Betaine (Lauryl Betaine), *Limonene (*Limonene), Perfume (Perfume), Colour 42090 (Colour 42090), Colour 45410 (Colour 45410) PRESERVATIVE: NONE

  • The Body Shop Camomile Cleansing Butter

Ethylhexyl Palmitate (Skin Conditioning Agent), Synthetic Wax (Binder/Emollient), PEG-20 Glyceryl Triisostearate (Skin Conditioning Agent), Olea Europaea Fruit Oil/Olea Europaea (Olive) Fruit Oil (Emollient), Butyrospermum Parkii Butter/Butyrospermum Parkii (Shea) Butter (Skin Conditioning Agent - Emollient), Caprylyl Glycol (Skin Conditioning Agent), Tocopherol (Antioxidant), Parfum/Fragrance (Fragrance), Aqua/Water (Solvent/Diluent), Linalool (Fragrance Ingredient), Limonene (Fragrance Ingredient), Helianthus Annuus Seed Oil/Helianthus Annuus (Sunflower) Seed Oil (Emollient), Anthemis Nobilis Flower Extract (Natural Additive), Citric Acid (pH Adjuster). PRESERVATIVE: NONE (although glycols can preserve, limonene helps and the pH is probably low - it contains a small amount of water).  There could be a hidden preservative in this under 'parfum' that can not be guaranteed.

  • Suki Foaming Facial Cleanser

Sucrose, potassium cocoate (saponified coconut oil)†, oryza sativa (rice) flour†, cymbopogon flexuosus (lemongrass) oil, avena sativa (colloidal oat) kernel flour, citrus aurantifolia (lime) peel oil, citrus aurantium dulcis (sweet orange) peel extract, squalane, chamomilla recutita (matricaria) flower/leaf extract, calendula officinalis (calendula) flower extract, lavandula angustifolia (lavender) flower extract, carthamus tinctorius (safflower) seed oil, olea europa (olive) fruit oil, ascophyllum nodosum (seaweed) extract†, fragrance (parfum)*, limonene*, citral*. *components of 100% pure natural fragrance and/or steam-distilled/cold-pressed essential oils. PRESERVATIVE: NONE

LIST OF ANHYDROUS PRODUCTS WITH A NON-BROAD SPECTRUM PRESERVATIVE NOT PROTECTIVE AGAINST MOULDS

  • Soap and Glory Sugar Crush Body Scrub

Glycerin, Maris sal (Sea salt), Sucrose, Polysorbate 20, Glyceryl stearate, Butylene glycol, Sodium chloride, PEG-100 stearate, Caprylic/capric triglyceride, Prunus amygdalus dulcis (Sweet almond) oil, Macadamia integrifolia shell powder, Citrus aurantifolia (Lime) oil, Dioctyl Adipate, Parfum (Fragrance), Benzyl alcohol, Ricinus communis (Castor) seed oil, Stearalkonium hectorite, Talc, Propylene carbonate, Propylene glycol, BHA, Propyl gallate, Limonene, Linalool, Citral, Citric acid, CI 77492 (Iron oxides), CI 77499 (Iron oxides), CI 77491 (Iron oxides). PRESERVATIVE:  BENZYL ALCOHOL (PARTIALLY WATER SOLUBLE)

  • REN Rosa Centifolia™ No.1 Purity Cleansing Balm

Prunus Amygdalus Dulcis (Sweet Almond) Oil, Cetearyl Ethylhexanoate, Glyceryl Cocoate, Caprylic/Capric Triglyceride, Glyceryl Stearate, Glyceryl Dibehenate, Tribehenin, Glyceryl Behenate, Butyrospermum Parkii (Shea Butter), Sodium Cocoyl Glutamate, Parfum (Fragrance), Rosa Centifolia Flower Extract, Cymbopogon Martini Oil, Viola Odorata Extract, Anthemis Nobilis (Chamomile) Flower Oil, Lecithin, Benzyl Alcohol, Oryzanol, Tocopherol, Citronellol, Geraniol, Eugenol, Linalool PRESERVATIVE: BENZYL ALCOHOL

  • Eve Lom Cleanser

Paraffinum Liquidum (Mineral Oil), Peg-30 Lanolin, Cetearyl Alcohol, Bis-Diglyceryl Polyacyladipate-2, Aluminum Stearate, Theobroma Cacao (Cocoa) Seed Butter, Peg-75 Lanolin, Phenoxyethanol, Eugenia Caryophyllus (Clove) Leaf Oil, Humulus Lupulus (Hops) Oil, Chamomilla Recutita (Matricaria) Flower Oil, Eucalyptus Globulus Leaf Oil, Bht PRESERVATIVE: PHENOXYETHANOL (OIL SOLUBLE)

  • Boots Botanics Superbalm

Olea europaea (Olive) fruit oil*, Prunus amygdalus dulcis (Sweet almond) oil*, Cera alba (Beeswax)*, Butyrospermum parkii (shea) butter*, Cetearyl alcohol, Simmondsia chinensis (Jojoba) seed oil*, Rosa canina seed oil* PRESERVATIVE: NONE

  • Sanctuary Hot Sugar Scrub (sold in Boots)

PEG-8 • Zeolite • Sucrose • Kaolin • Glycerin • Zinc Oxide • PEG-220 • Parfum (Fragrance) • Silica • Benzyl Salicylate • Linalool • Benzyl Benzoate • Hexyl Cinnamal • Limonene. PRESERVATIVE: NONE (BUT THERE APPEARS TO BE HIGH LEVELS OF GLYCERIN AND ZINC)

  • Ole Henrickson Salt scrub

Glycerin, Sea Salt, Sodium Chloride, Butylene Glycol, Calcium Carbonate (CI77220), Caprylic/Capric Triglyceride, Glyceryl Stearate SE, Peg 100 Stearate, Ceteth-2. PRESERVATIVES: NONE (glycerine, glycols, salt are a hurdle but they are not official preservatives) http://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_s_006.pdfhttp://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32013D0674#ntr11-L_2013315EN.01008301-E0011http://oxfordbiosciences.com/safety/http://www.staceyirvingconsultancy.co.uk/page_2785678.html