Isopropanol as a preservative in creams

Is isopropanol at a low concentration (below 3%) as effective as part of a preservative system as using something like phenoxyethanol or sodium benzoate, or is the inclusion rate needed for longer-term preservation efficacy using isopropanol much higher?

Comments

  • Never seen any evidence  of that- did you see that information somewhere? Usually you need very high concentrations of alcohol (>60%) for adequate preservation. I found this paper from 2010 using 5% ethanol in combination with other preservatives, but I don't think this paper is robust enough to actually determine if the ethanol was  truly helpful.
    https://pdfs.semanticscholar.org/629f/e402ae18d7c597b95ef1467a34aea7a0d86a.pdf?_ga=2.91159578.1816399624.1581518977-1159633445.1581518977
  • I thought 20% was the necessary amount for adequate preservation. I had seen at least 1 face cream formula with isopropanol listed in the ingredients list close or alongside to phenoxyethanol which led to me suspecting it was being used as a preservative in the formula.
  • https://www.cdc.gov/handhygiene/science/index.html
    https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html

    Isopropyl alcohol (20%) is effective in killing the cysts of Acanthamoeba culbertsoni (560) as are chlorhexidine, hydrogen peroxide, and thimerosal  (from the second link)

    For the face cream you saw, isopropanol  near phenoxyethanol means near 1% and that would more likely be a solubilizer/solvent for some other ingredient
  • I thought 20% was the necessary amount for adequate preservation. I had seen at least 1 face cream formula with isopropanol listed in the ingredients list close or alongside to phenoxyethanol which led to me suspecting it was being used as a preservative in the formula.
    Without seeing the list of course I’m just guessing but I think it may have been for solubilization. 

    I have read anywhere from 20-70% is required for preservation. Makes me question my sources... -_-

    Does anyone know if there are any synergies between say ethanol/isopropyl alcohol and phenoxyethanol?
  • Werps, I didn’t see EV’s last post but I’ll leave mine as a +1.
  • I have no clue about synergistic effects between phenoxy and other alcohols. I suspect Monopropylene glycol could help phenoxyethanol just as it seems to help parabens.
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