Hexanediol, Pentanediol & Ethylhexylglycerin as Preservative

I have found this study on alternate preservation,
http://kmbase.medric.or.kr/Main.aspx?d=KMBASE&i=0604520180440040363&m=VIEW. (document can be downloaded)
which concludes that below combination can be used as a preservative.
1% 1,2-hexanediol and 1% 1,2-pentanediol with 0.1% ethylhexylglycerin

Does this mean that we can use the above combination to preserve our products? Is it practical, or should I start with doubling the above % and then do testing. 

Are there any flaws in above study?


  • PharmaPharma Member, Pharmacist
    There are likely several flaws in there...
    Anyway, don't forget that there are also 5% 1,3-butylene glycol in said formulation. Which brings me to the first flaw: no control without it but only your 3 preservatives/boosters. Though it is possible that there wouldn't be much of a difference or that 2-3 times higher amounts of diols are needed if 1,3-butylene glycol isn't used. Likely depends on the formulation (water activity!).
    Try it out.
    Hexanediol is approximatively twice as active as pentanediol but the latter also exists as Ecocert naturally derived product. The few trial formulations I did turned out less viscous with pentanediol but I wouldn't interpret too much into that finding. You don't necessarily need both and you may try out just one but at higher %. Although some stuff I've read implies a broader spectrum if both are mixed.
    Ethylhexylglycerin is often used at 1/10 of the preservative (different blends with phenoxyethanol or chlorphenesin are commercially available) and acts as booster; meaning it lowers MIC (or lowers the amount of preservative needed) and apparently broadens the spectrum.
    Me personally, I can't/don't want to run challenge tests because I don't sell, so I prefer using not too much but still enough to be on the safe side. I'd at least consider to include something like GMCY or phenylpropanol to further boost the blend of 1,2-XXXdiol and ethylhexylglycerin.
  • ThotaThota Member
    Thanks @Pharma for your reply. Your posts are always very informative.

    Yes totally forgot there is 5% BG and 5% glycerin in the formula.

    Planning to test above combo deleting glycerin, I am primarily looking at this combo for water based serum with pH6.5

    I used to use PE 9010 but phenoxyethanol is causing reactions to some customers and also found some studies that it is less microbiome friendly. Glycols and EHG seems Skin Microbiome friendly. 
    Will be trying below combination 

    5% BG
    0.2% EHG
    2% HG
    Pheneylpropanol 0.2%

    Alternatively I am also planning to try just the below combo 
    3% Petylene GLycol 
    0.4% Pheneylpropanol
    Above combo is from Dermosoft 250 data shets for pH 6.4 solution 

    GMCY would be great but it is not so helpful for water only products

    Planning to buy an incubator and few microbial testing kits, to start this testing.

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