It’s a common myth that anti-oxidants like vitamin E, Grapefruit Seed Extract and rosemary extract are preservatives but they are not – http://swiftcraftymonkey.blogspot.co.uk/2012/01/when-should-you-use-preservative.html Oxidation of oils and butters leads to rancidity and anti-oxidants slow down this process. These anti-oxidants do not prevent bacteria, yeast, or mold from spoiling your product. (Yeasts and moulds are fungi).
There have been serious problems from spoiled and contaminated cosmetics.
“In a Barcelona hospital, five intensive care patients became infected with a deadly bacteria called Burkholderia cepacia (B. cepacia). Officials traced the illness to a moisturizing body milk used in the patients’ care.” – see www.happi.com/contents/view_features/2008-04-30/preservative-market-update-85454/#sthash.J4GgNxQm.dpuf
“Bacteria like Pseudomonas can cause all kinds of health problems including skin and eye infections, toxic shock, strep throat, and even food poisoning. Yeast like Candida albicans can cause thrush. And many other bacteria can cause your products to smell awful, change color or otherwise break down.” – quote taken from – http://chemistscorner.com/how-to-prevent-contamination-in-cosmetic-products/
In 1947, in New Zealand, unsterilised talc caused 25 cases of Tetanus, and 4 fatalities – http://atojs.natlib.govt.nz/cgi-bin/atojs?a=d&d=AJHR1947-I.22.214.171.124&cl&srpos=0&e=——-10–1——0–&st=1
If your product contains water (including hydrosols, floral water, aloe vera, goat’s milk which all contain water) or will come into contact with water (eg a scrub used with wet fingers) a preservative is essential to help prevent microbes (bacteria, mold, and yeast) growing. Preservatives stop growth by acting on spores when they germinate and killing cells (usually by disrupting cell membranes) or by making the product hostile to growth.
Ingredients to add to help the preservative: – (a) add 0.1% disodium EDTA into your heated water phase but bear in mind that EDTA is precipitated from solution by most polyvalent cations so will be less effective. (Divalent cations/EDTA salts are real soluble – EDTA can mobilise otherwise insoluble heavy ; (b) for a more “natural” but much weaker alternative, Dissolvine GL 47-S; and (b) an anti-oxidant to help slow down oil rancidity slightly such as vitamin E at no more than 0.1%.
If you decide not to use a preservative, please store your product in the fridge and use it within 1 week but note you cannot rely on sight to know that your product is fine for use – the product might look and smell just fine, but when we run them through micro tests, the bacteria, yeast, and mold count is off the chart.
If you are making a product with lots of actives, botanicals etc (which are notoriously difficult to preserve) then you need a preservative that can cope so that will limit your choices. So do, where possible, reduce any components that may be nutritive to the bacteria and fungi e.g. specifically, clay, goat’s milk, aloe vera, hydrosols, floral waters, extracts, hyaluronic acid and more generally: carbohydrates, proteins, organic acids, inorganic salts and vitamins. I would suggest either Germaben together with a couple of chelators or consider combining two preservatives like liquid Germall Plus and Germaben II together with chelators but do check that the ingredients which make up the preservatives are not the same as together they might exceed the legal limit. Yes it is possible to use, for example, 50% aloe vera or hydrosol in a formula and still pass preservative tests but do ask the supplier for a copy of the micro testing for the batch of aloe/hydrosols you are buying (could be in the Certificate of Analysis) – check it shows less than 100 cfu/gram or ml and no staph, Candida albicans or Gram negative bacteria!.
There are many different types of preservatives that it can be quite confusing. If you are preserving a jar product (with a largish headspace), including phenoxyethanol in your preservative mix is a very good idea to have in there as it will keep the headspace clean.
As a general rule it’s always a good idea to mix up your preservatives, as they all have their strengths and weaknesses in what they kill, so a combo can give you a broad spectrum, and keep the overall levels of each down low, which helps with both stability and irritancy. Most of the preservatives listed below are a mixture of preservatives.
I have listed the main preservatives below in the “traditional” and more “natural” categories. Please, please use a preservative which is broad spectrum. This means it guards against (a) gram positive and gram negative bacteria, (b) mold; and (c) yeast. See http://swiftcraftymonkey.blogspot.ca/2010/10/preservatives-what-can-get-into-our.html
The finished pH of the product will have a major impact on the efficacy of the preservative. Bacteria thrive in the pH range of 5.5 to 8.5, the typical pH range for bacterial growth is pH 4 to 9. Yeasts and filamentous fungi prefer the pH range 4-6 but growth generally occurs within a range of pH 3 to 10. Microorganisms present in manufacturing environments are often acclimated to thrive beyond these limits of pH. In fact, environmentally isolated microbes have been known to persist within a pH range of 2.5 to 10.5. Use a good antifungal preservative at a low pH or a good antibacterial preservative at a high pH may provide a better broad spectrum preservation. If the pH is high enough, for example, over pH 10, a preservative may not be needed.
Reducing the amount of unbound water in your formulation will inhibit microbial growth. Lowering the water activity and water partitioning of a preservative prevents the migration of it away from the aqueous phase. This can be accomplished by increasing glycerin and other polyols (propylene gycol) above 5%; reducing the surface tension between the oil phase and water phase with functional siloxanes, particularly dimethicone polyethers and flurosilicones; and minimising sources of energy for microbial growth (e.g., sugars and alcohol sugars, peptides, carbohydrates, anionic surfactants, proteins, plant extracts (eg aloe vera, starch), vitamins, clay compounds and natural gums and cellulose thickeners), fluorosilicones.
UV sunscreens can deactivate formaldehyde-releasing preservatives, and surfactant micelles tend to capture and inhibit preservative activity. Preservatives can also be compromised if there are solid particles (eg talc, inorganic sunscreens, clays, pigments) as they may absorb onto the surface of the particles and so become unavailable within the water phase.
Ingredients that enhance preservative efficacy: solutes (salts and high concentration of sugars), esters, cationic and anionic surfactants, humectants (glyerin, propylene glycol), phenolic antioxidants (BHT), chelators (EDTA), fragrances.
Do put in place a strict Good Manufacturing Practices (GMP – http://en.wikipedia.org/wiki/Good_manufacturing_practice) protocol to include microbiological testing of raw ingredients and process water, equipment sanitization.
Design your packaging so it prevents contamination during use and check the material the containers you put the product into are made from as adsorption onto excipients, especially those with large surface areas or on to container / closure systems can also remove preservative(s) from solution for example:-
– benzyl alcohol by polyethylene
– phenoxyethanol by pvc plastic, cellulose based excipients
– sorbic acid/sorbates by plastics (polypropylene, PVC and polyethylene)
After deciding which preservative to use, you will need to ensure that your preservative is working and will continue to work over a long period of time. This is generally confirmed by having your product tested by a lab. They will challenge test your product and let you know if it has remained microbe-free after repeated exposure to the most common microbes. Even the most time-tested preservatives can fail to work if inadequate amounts were used or if they were broken down by heat, pH or other factors including failed GMP’s.
1. Minimise sources of energy for microbial growth (aka “bug food”) – eg fruit, botanicals, tea, lecithin, mineral water, milk of any kind, honey, hydrosols, floral waters, aloe vera, extracts, protein, clay, powders, starches etc. Yes it is possible to use, for example, 50% aloe vera or hydrosol in a formula and still pass preservative tests but do ask the supplier for a copy of the micro testing for the batch of aloe/hydrosols you are buying (could be in the Certificate of Analysis) – check it shows less than 100 cfu/gram or ml and no staph, Candida albicans or Gram negative bacteria!.
2. Double check against against the reviews of the preservatives below whether your preservative is truly broad spectrum (If your preservative isn’t one of the 27 reviewed below do check for it here – https://www.facebook.com/groups/makingskincare/permalink/529462787179550/ (If you can’t access this second link do first join the Making Skincare facebook discussion group here – https://www.facebook.com/groups/makingskincare/)
NB: Phenonip, germaben and liquid germall plus are effective preservatives.
3. Add glycerin and other polyols
4. Add 0.2% disodium EDTA into the heated water phase
5. Switch to packaging which the customer can’t contaminate easily – jars are the worst for contamination.
6. Reduce the pH to between 4 and 5 if possible.
7. Sanitise your equipment with 70% IPA
8. Use distilled, deionised or purified water, not tap/faucet or mineral water
9. If your water isn’t micro checked, heat and hold your water phase at 75c/167f for 20 minutes – this will kill some of the non-endospore forming bacteria. (If your preservative can withstand heat put it in the heated water phase rather than the heated oil phase. This improves preservative contact with the water phase so that it is not partitioned in the water-oil interface).
10. If possible micro test all of your raw materials.
11. Use good GMP – http://www.mariegale.com/good-manufacturing-practices/gmp-basics.html
12. Don’t rely on sight, smell – one can put 100,000 bacteria into a milliliter of water and the water will appear to the naked eye to be crystal clear and usually won’t smell bad. Most cosmetics tested have counts ranging into the tens of thousands or millions of cells per milliliter have subtle or no aesthetic differences from sterile samples. The only way to know if your preservative system is working is to get it tested.
PRESERVING PRODUCTS WITH PH BETWEEN 8 AND 10 e.g. LIQUID SOAP
Cold process soap (made with sodium hydroxide) does not need a preservative. For other high pH products such as liquid soap, generally if the pH is above 10 a preservative may not be required. If the pH is below 10, an expert microbiologist advises liquid germall plus can be used (despite the supplier recommended use below pH8). Alternatively, Suttocide A (see below for downsides) or Glydant Plus can be used.
PRESERVING ANHYDROUS EG SCRUBS
If water may be introduced to the product or the product used in a humid bathroom then a preservative is advisable. An expert microbiologist advises that if trying to preserve an anhydrous product (including all oil+sugar/salt scrub) the oil soluble preservative will get locked in the oils so will not reach any water, if water was introduced into the product. So if you added an oil soluble preservative then that preservative will stay in the oils and not move over to where the water is located to protect that water against bacteria and mould so would be useless. So contrary to what you may have read, we should really use a water soluble preservative in an anhydrous product which means we’d need to add an emulsifier to get that preservative mixed in properly with the oils.
GLYCERIN / ALCOHOL / HONEY / GRAPEFRUIT SEED EXTRACT AS PRESERVATIVE??
– Glycerin is a very effective preservative – in medicine, you will frequently find glycerites as a delivery vehicle (especially in children’s and herbal medicine) where the active component is preserved and then ultimately delivered in a water soluble solvent (glycerin) as an alternative delivery mechanism to alcohol. To be effective as a preservative, you need to have 70% glycerin content in your formula. The downside is glycerin is very, very sticky – not a great skin feel.
– Ethanol (not vodka, instead use 190 Everclear alcohol or skin safe cosmetic use denatured alcohol) anything containing 20-25% ethanol is self preserving. Alcohol is astringent so not a great add if you want a moisturising lotion. It is also a known irritant so if you have sensitive skin, a lotion containing alcohol could sting! You might see it in a lotion with alcohol as a cooling foot lotion as it will evaporate from your skin. However note, you might see Ostwalt Ripening in an O/W emulsion resulting in flocculation and ethanol can diminish foaming of surfactant-based products like shampoo.
– Honey – not advisable – see http://swiftcraftymonkey.blogspot.co.uk/2012/05/honey-few-studies-ive-found-about-its.html
– Grapefruit Seed Extract,(not recommended). GSE is not what you would consider to be a regular extract. Citrus seed extracts are not all-natural – they are chemically derived from the seeds of citrus fruits. It is made IIRC by reacting with ammonia, so is more like a quat in some ways. There are concerns that the limited preservative properties GSE does have are in fact due to added preservatives like parabens – see http://swiftcraftymonkey.blogspot.co.uk/2010/10/preservatives-grapefruit-seed-extract.html
– Liquid Germall Plus – this effective and easy to use preservative is a favourite amongst DIYers including swiftcraftymonkey – INCI: Propylene Glycol (and) Diazolidinyl Urea (and) Iodopropynyl Butylcarbamate. Use 0.5% cool down phase – good for emulsions e.g. lotions and aqueous mixtures but can’t be used in all oil creations. pH range: 3-8 however an expert microbiologist advises it can be used at a higher pH. In the US, do not use in aerosols/sprays and in the EU do not use in body creams/lotions.
IMPORTANT: – PARBENS: Some preservatives (mainly parabens – Phenonip) can be inactivated by non-ionic emulsifiers and fatty alcohols/acids, esters, polysorbates. Non ionic surfactants can form micelles with preservatives which contain lipophilic groups turned inward. Parabens to the extent that they are lipophilic can find their way into these centers so are best not used. Do not use polysorbates or cetearth-20. These ingredients will partially inactive the preservative: polysorbate 20 and ceteareth-20/polysorbate 20 used above 2.5%. (Liquipar PE and Germaben II are not affected by non-ionic ingredients). Parabens are inactivated by strong hydrogen bonders such as ethoxylated compounds, cellulose gums, lecithin. Parabens are very oil soluble so tend to migrate to the oil phase, where their activity is greatly diminished, particularly if there are a lot of esters and vegetable oils so it may not be suitable for high oil loads in an emulsion. Parabens must be added to the water phase or they will remain in the oil phase and have reduced activity against bacteria and fungi. pH range for parabens: 3.5 to 6.5 (optimal) but can be used up to pH 8.
– Phenonip – another effective preservative and a great single addition preservative (Note: this preservative will in the future be re-formulated as Isobutylparaben will be removed). Add 1% to the heated water phase as it dissolves around 60˚C to 70˚C. If you want to use it in a cold product, heat up some propylene glycol or glycerin and add the Phenonip to that before adding it to your product. If you want to use it in a surfactant mix – say, a shampoo bar or body wash – then add it to the heated surfactant phase. INCI: Phenoxyethanol (and) Methylparaben (and) Ethylparaben (and) Butylparaben (and) Propylparaben (and) Isobutylparaben. Suitable for all use in emulsions and aqueous products. NOTE: Phenonip is inactivated by some non-ionic ingredients, such as polysorbates (at 5%, Phenonip is completely inactivated by polysorbate 80), and slightly by polysorbate 20 and 80 at 2.5%. It doesn’t do well with ceteareth-20 – it’s inactivated by 5% – but it is not affected by cetearyl alcohol. Parabens are inactivated by strong hydrogen bonders such as ethoxylated compounds, cellulose gums, lecithin. See above paragraph for more warnings. pH range: 3-8. This preservative is actually unsuitable for preserving all oil products – see paragraph above entitled “Preserving Anhydrous”.
– Germaben II – Another very effective preservative (but see above as it is inactivated by certain ingredients) – very good for hard to preserve products e.g. those with lots of extracts. INCI Propylene Glycol (56%),Diazolidinyl Urea (30%), Methylparaben (11%), and Propylparaben (3%), 0.5% to 1% in the cool down phase. Water soluble. It is ready-to-use in emulsions with an oil phase of about 25% or less and water soluble formulations. pH range: 3-7.5
– Germaben II-E INCI: Propylene Glycol, Diazolidinyl Urea, Methylparaben, Propylparaben. A popular preservative, Germaben II-E can be used in problem formulations without the need for additional co-preservatives (but see above as it is inactivated by certain ingredients). Use Germaben II E (as opposed to Germaben II) when making emulsions that have 25% oil or more. Add slowly after emulsification and prior to addition of fragrance. Or add to fragrance and add mixture slowly to finished formulation after tempertature has dropped below 60C (140F). Use level 1%. It is a complete preservative in that it covers microbial, fungus, and yeast. pH range: 3-7.5
– Suttocide A INCI: Sodium Hydroxymethylglycinate. One of the few preservatives which can handle a high pH. Suttocide is a good bet, but may need a bit of supplementation with other preservatives to mop up any yeasts and moulds. It has good anti-bacterial properties, and its fungi, mould, and yeast killing properties increase with the quantity used. So you’re better off using up to 0.5%! It is water soluble. Add to the cool down phase before adding fragrance (below 60˚C), but note special considerations for different products. For shampoo, body wash, and other surfactants, add it at 0.1% to 0.3% when it’s below 60˚C but before you thicken it with salt. For conditioners, use it at 0.1% to 0.2%: It can interact with your quats, but it won’t be de-activated by them. It’s suggested at 0.5% for emulsions – add below 60˚C but before you add the fragrance. And if you want to use it to gel your carbomers – read the data sheet for more information! The different amounts correspond to how hard the product is to preserve. However, do check the pH on your final product as it can make your product more alkaline. Citral (a component of some essential and fragrance oils e.g. citrus) WILL react with Suttocide A and effect a color change (light pink to indian paintbrush red) in the formulation. http://www.aromaweb.com gives components of essential oils. pH range: 3.5-12
Most companies use a blend of preservatives to cover the range of bacteria and fungi that might be encountered. If you would like to create your own blend, a good starting “traditional” preservative combination could be (so long as there is not a high amount of oils/esters and no polysorbates): 0.5% Phenoxyethanol, 0.3% Methylparaben and 0.18% Propylparaben plus a chelator, for example, 0.05% disodium EDTA. Also these alternatives: Suttocide A with sodium benzoate or liquid germall plus with sodium benzoate.
MORE “NATURAL” PRESERVATIVES although note some are not so effective. This is especially true when using natural antimicrobials and or other “mild” antimicrobials. Every formula should undergo stability and microbial testing to ensure adequate preservation.
If you have decided to make “all-natural” skin care products – you will not find a product on the market that is all-natural, safe for use and will protect your product from the wide range of microbes and fungi out there. Essential oils such as tea tree have been suggested, however, the percentage required to be effective as a preservative would not be safe to use on the skin. With the more newer more “natural” type preservatives, yeast/mold can be an issue and sodium benzoate is usually added to help. Changing the pH – If you add such an organic acid then you will need to change the pH so it is more acidic. To do this you will need an accurate pH meter to accurately measure the pH of your product. Dissolve citric acid in some water and add to the cool down phase. Approximately 0.2% citric acid will decrease pH each time by about 0.9 or so.
The preservatives below are not Ecocert approved
– Mikrokill COS / GFguard COS – (INCI: Phenoxyethanol (and) Caprylyl Glycol (and) Chlorphenesin) 1% cool down phase – for products containing both oil and water. But see warning note below regarding caprylyl glycol. For an all water solution as the capryl glycol is oil soluble, you need to add a solubiliser such as polysorbate. pH range: 3-8
– Jeecide® CAP-5. INCI: Phenoxyethanol (and) Caprylyl Glycol (and) Potassium Sorbate (and) Water (and) Hexylene Glycol. See note below regarding possible emulsion instability. For highly aqueous systems, it is not water soluble so needs the addition of a co-solvent, coupling agent or surfactant e.g. poysorbate 20 in a 1:1 ratio to make it water soluble. Cool down phase – use level: 1%. Keep pH below 6. This preservative has been reported to have worked well with some formulas.
NOTE – caprylyl glycol which is in mikrokill COS, Jeecide CAP-5 and the optiphens can destabilise if your emulsion system is fragile or on the edge even if added at cool down. Caprylyl glycol has an HLB of 7.5 – if you are using the HLB system to tailor make an emulsifier, you should include this item as well as Ethylhexylglycerin (HLB 7.5) if you are using Euxyl PE 9010 in your HLB calculations (see the free downloadable HLB calculator in this blog). Also for stability add a gelling agent like sodium polyacrylate.
– Optiphen / GFphen PCG – Phenoxyethanol (and) Caprylyl Glycol. Not recommended. Add up to 1.5% (1% leave on products) at cool down but see above note. Can cause emulsion instability – see notes above and below for tips. Non ionic surfactants may decrease the efficacy of this preservative. For an all water solution as the capryl glycol is oil soluble, you need to add a solubiliser such as polysorbate. Do not use for surfactants. Best used with a chelator and do add another preservative to help combat fungus. pH range: 4-8. This preservative is actually unsuitable for preserving all oil products – see paragraph above entitled “Preserving Anhydrous”.
– Optiphen plus – INCI of Phenoxyethanol (and) Caprylyl Glycol (and) Sorbic Acid – use 1.5% (1% leave on products) – to help guard against emulsion instability and thinning, remove some of the emulsion, add the preservative, pre-blend well and then add back to the entire emulsion. Use a gelling agent such as sodium polyacrylate to help stability. If you are using dimethicone, add it in the heated oil phase (and if you are using cyclomethicone add just after the emulsion has formed) so it emulsifies better as silicones can be tricky for some emulsifiers to emulsify. Do not use with salts e.g. sodium lactate as the pH tends to drift and destabilise the emulsion further. The sorbic acid augments yeast/mold coverage. Sorbic acid is sensitive to oxidation resulting in discoloration and a potential petroleum odor. It is also is unstable at temperatures above 38c To be effective the pH must be 6 or below. Add at cool down – see note above. For an all water solution as the capryl glycol is oil soluble, you need to add a solubiliser such as polysorbate. Cosmetic chemists have reported effective preservation with this preservative with certain formulas. Do not use for surfactants. pH range: up to 6
– Iscaguard BOA / GFecosafe WW – water soluble preservative – pH up to 5 (use citric acid to lower the pH – see above), use 1% -INCI: Benzyl alcohol, Dehydro Acetic acid, Sorbic acid and Benzoic acid. Sorbic acid is sensitive to oxidation resulting in discoloration and a potential petroleum odor. It is also is unstable at temperatures above 38c. If using it in all water solution then heat to 40c to disperse it. Note: over time (6 months) benzyl alcohol oxidises to benzaldehdye which smells quite strongly of almonds. The dehydroacetic acid protects against fungi and can sometimes cause a yellowing effect which can be limited by adding antioxidants e.g. BHT or sodium metabisulfite. When used with anionic surfactants such as ether sulfates and cocamidopropyl amides, there could be a darkening effect. I was unable to find much information about this product so do check with your safety assessor.
– Preservative 12 / euxyl® PE 9010 / ethox / GFpreserve POG / INCI: Ethylhexylglycerin (oil soluble and soluble in glycerin) and Phenoxyethanol. Do not use this preservative with water soluble oils or high load of surfactants. Use level: 1.1% cool down phase. Not very water soluble so needs glycerin in an aqueous solution. Note: Ethylhexylglycerin can destabilise your emulsion if your emulsion is fragile or on the edge so do include it in your HLB calculation. pH range: up to 12 (but more likely up to pH8).
– Naticide – Expensive. INCI fragrance/parfum. It has a vanilla/almond smell – 1% cool down phase (water soluble) and mix well. pH range: 4-9. With this preservative do add a chelator and combine it with 0.5% sodium benzoate and the pH should be reduced to 4.5.
– Preservative K / euxyl k700 – INCI name: Benzyl Alcohol, Phenoxyethanol, and Potassium Sorbate – take the pH down to 5 or below in order for the preservative to work. But note, however, the preservative itself is alkaline so it will increase the ph. Benzyl alcohol is good to very good against Gram+ve, moderately poor against Gram-ve, poor versus fungi and moderately poor against yeast, it has low water solubility, is volatile (so should be used with an antioxidant) and may be inactivated by nonionic surfactants such as polysorbates. Note: over time (6 months) benzyl alcohol oxidises to benzaldehdye which smells quite strongly of almonds. Use 1.5% cool down phase.
– Leucidal Liquid SF (inci Lactobacillis Ferment) – water soluble. Bring pH down to 5 and add below 40c however it’s not strong against mold so you could try adding sodium benzoate e.g. 4% Leucidal Liquid SF and 0.5% sodium benzoate.
– Leucidal Liquid – Not recommended – failed Brambleberry’s challenge testing (mould) and some cosmetic chemists have also reported similar results INCI: Leuconostoc/Radish Root Ferment Filtrate. pH range: up to 6
– Leucidal® Liquid PT – Not recommended by microbiologists. pH range: up to 6
– Kathon CG. INCI: Methyl chloro isothiazolinone, Methyl isothiazolinone). Popular in wash-off products but do not use in leave on products like creams or lotions but it’s not great with high pH’s (>8), Sulfites or SO2 and has the same sort of levels of allergic responses as do fragrances, so is not great for use in sensitive skin/hypoallergenic products. Legal limit in the EU: 0.1% for wash off. Use 0.04% for leave on products (not recommended). Typical use level is around 0.05- 0.07%. Cool down phase. pH range: up to 7
– Phenoxyethanol. (Use up to 1% cool down phase). It is most active against Gram-negative bacteria. It is used in combination with other preservatives, in part because its activity is weak against yeast and mold. Phenoxyethanol is stable up to 85°C (185°F) and has useful activity from pH 3 to 10. Phenoxyethanol is soluble in most oils. It is also soluble in water from 0.5 to 2.67 grams per 100 grams of water. It is miscible with propylene glycol and glycerin. Phenoxyethanol is inactivited by highly ethoxylated compounds including polysorbates so do not use with surfactants. In surfactant solution systems, the water must be saturated with phenoxyethanol for activity. If the level is too low, it acts as a nutrient for bacteria. However, it can cause viscosity issues in detergent products, and make them difficult to thicken in certain cases. To boost activity against yeast and mold, consider combining this preservative with 0.5% sodium benzoate and in order for this to be sufficient the pH should be reduced to 4 to 4.5. Phenoxyethanol has the advantage that it is slightly volatile so it will protect the “head space” or vacant air space above the product in the bottle.
– NatureCide/PhytoCide (INCI: Aspen Bark Extract). This product, has a pretty big hole in it’s coverage. It needs to be reinforced with a fungicide (0.5% sodium benzoate) as well. Not recommended. pH range if used on it’s own (not recommended): 3-9
The preservatives below are Ecocert approved
Suggested starting Ecocert approved preservative combination: sodium benzoate 0.35%, potassium sorbate 0.35%, benzyl alcohol 0.2% (all three are problematic at much higher levels) together with disodium EDTA at 0.05% or sodium phytate. The pH must be brought down to 5 to 5.5.
– Glyceryl Caprylate/Dermosoft GMCY – oil soluble preservative but add it to the heated water phase so it does not get partitioned at the oil-water interface. Do not use with surfactants. For use in aqueous products, add it to glycerine and use a solubiliser. WARNING: It can destabilise your emulsion if your emulsion is fragile (so do include it as part of your HLB calculation and use a gelling agent such as sodium polyacrylate) and it can also “thin” emulsions. Effective against bacteria and fungus but weak against mould. It is not actually listed as a preservative, and as such doesn’t have a maximum usage level. It is listed as a wetting agent or emollient component. Use up to 1% and pair it up with a preservative which is effective against mould such as p-Anisic acid for a “preservative-free” formula. Keep the pH below 7 to avoid hydrolysis.
– p-Anisic Acid/Dermosoft® 688 eco the INCI is Parfum. Use:0.3%. Water soluble. Add to the heated water phase to dissolve the powder and pre-dissolving with glycerine can also help. Guards against mould but is weak on bacteria and fungus. Adjust the pH to 5.5 or below in order for it to be effective against mould. Pair up with glyceryl caprylate for a “preservative-free” formula.
– Mikrokill ect / preservative eco / geogard ect / Plantaserv M. INCI: Benzyl Alcohol & Salicylic Acid & Glycerine & Sorbic Acid (reduce the pH to 5.5 or below). Use 1.1% cool down (below 45c). It is insoluble in water so requires adding to something like glycerine or a glycol. It can affect the viscosity of some systems causing emulsion stability Sorbic acid is sensitive to oxidation resulting in discoloration and a potential petroleum odor. It is also is unstable at temperatures above 38c. Note this preservative only has a 1 year shelf life and it failed Aromantic’s challenge test when used with clay and over time (6 months) benzyl alcohol oxidises to benzaldehdye. This smells quite strongly of almonds.
Note – Some preservatives can irritate e.g. potassium sorbate (see below) – for hypoallergenic products you can use a blend of Methylparaben, Propylparaben and Bronopol which are effective
– Euxyl K712 INCI sodium benzoate and potassium sorbate and water:-
o (Benzoic acid/potassium benzoate/sodium benzoate – More stable than potassium sorbate and less pH sensitive. Only effective in acidic formulations with optimal activity at or below pH 4.5. Benzoic acid is moderately good against Gram+ve bacteria, yeast and moulds, but moderately poor against Gram-ve bacteria. Benzoic aid is incompatible with quaternary compounds (eg honeyquat, polyquat) and non ionic surfactants. Do not use with Vitamin C or EDTA. .
o Sorbic acid/potassium sorbate – effective at a very acidic pH (eg 5) – good against mould and fungus and somewhat effective against bacteria. Sensitive to oxidation resulting in discoloration and unstable at temperatures above 38c. Some people notice a petroleum odour and experience flushing and reddening of face when sorbates are used in leave on products probably due to peripheral vasodilation effect of sorbates.
Note: the above used together are not sufficient against bacteria so do not offer broad spectrum coverage so you would need to add a microbicide. Cool down phase 1.5% – take the pH down to 5.5 or less for it to be effective.
– You can buy the sodium benzoate and potassium sorbate separately to use together however they are not effective against bacteria so you will need to also add a microbicide. Add at cool down, use citric acid to adjust final pH to 4.5 (see above) and for both pre-mix first with water before adding to cool down stage. Sodium benzoate: 0.5% (do not use with vitamin C) and potassium sorbate: 0.5% (or 0.39% if you are in the US).
– Microgard / Geogard Ultra / neodefend. INCI gluconolactone and sodium benzoate. Do not use with vitamin C. Use pH 5 or less. Make a solution with water and add 2% at cool down in water containing products. Water soluble. Can cause pH drift downwards – http://swiftcraftymonkey.blogspot.co.uk/2010/10/preservatives-geogard-ultra.html
– Geogard 221 / Cosgard (dehydroacetic acid and benzyl alcohol). Water soluble. usage: 1%. A little weak on mould so do add 0.5% sodium benzoate to cover this. Not approved for aerosol use. Ecocert approved. pH range: 2 to 6 – add at any stage. Over time (6 months) benzyl alcohol oxidises to benzaldehdye. This smells quite strongly of almonds. The dehydroacetic acid protects against fungi and can sometimes cause a yellowing effect which can be limited by adding antioxidants e.g. BHT or sodium metabisulfite. When used with anionic surfactants such as ether sulfates and cocamidopropyl amides, there could be a darkening effect.
– Optiphen BSB-N/Rokonsal™ BSB-N (INCI: Benzyl Alcohol, Glycerin, Benzoic Acid, Sorbic Acid). Over time (6 months) benzyl alcohol oxidises to benzaldehdye. This smells quite strongly of almonds. Ecocert approved. Sorbic acid is sensitive to oxidation resulting in discoloration and a potential petroleum odor. It is also is unstable at temperatures above 38c. Use for emulsions: 1% and shampoos/shower gels 0.5%. Add below 80c (recommended to add to the emulsion lukewarm). Important: pH must not exceed 5.4 for this preservative to be effective.