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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