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Glycols as preservatives
Hi Guys,
I hope everyone is well. I came across an interesting
product. It’s w/si emulsion without preservatives (I probably should say
ingredients that act solely as preservatives). It’s L’Oreal’s product, so no
double it’s properly formulated. Propylene glycol is the 3rd ingredient,
Dipropylene Glycol is 4th, then they have niacinamide (let’s guess
not more than 4%?) and Alcohol denat.Alcohol couldn’t be a preservative here as it’s too low in
the list, so I assume it’s the glycols.What amount of PG is considered self-preserving? I came
across different numbers from 10 to 20%. This paper:https://www.researchgate.net/publication/318380276_Antimicrobial_Preservatives
says 10% w/v of PG is sufficient in most situations although
certain molds require up to 30% for growth inhibition.I understand it would depend on many factors, but what do
you think is a reasonably safe range if we are talking about a cosmetic product
that is packaged in a pump bottle (no fingers), includes a chelator and contains
no bug food like proteins and clays?Thank you in advance!
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2 Replies
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It comes down to the water activity so you’d have to know how much water is in the system. See this video for an explanation.
https://www.youtube.com/watch?v=L3Xf45CeCQ0Dow suggests 25% PG to reduce chance of bacterial growth to almost nothing.
https://dowservice.custhelp.com/app/answers/detail/a_id/11499/related/1This is not a cosmetic product but the graph still holds true of PG solutions.
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Thank you very much @Perry. This is very useful.
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