Phenoxyethanol & Caprylyl Glycol heat stability

Hello, recently I've started to formulate my own cosmetics from home. I did a batch of lipgloss where I heated my ingredients together over a double boiler at a temperature of 80-100C. I was wondering what that would’ve done to my Phenoxyethanol and Caprylyl Glycol that was in there? Would it have degraded completely or is there a chance it would still have some antimicrobial properties? Also, it was heated for around 20-30 minutes. 

I now know I’m supposed to add my preservatives during the cool down phase but unfortunately I only learned that after I had heated my formula. Total newbie here! :smile:


  • EVchemEVchem Member
    On the brochure I have from Schulke  I see preservatives containing both those materials rated with a max temperature to 120 C (no info on time at max temp or degradation). 

    The easiest answer would be to get some kind of microbial test kit like mikrocount, it won't be perfect but it can tell you if you have obvious failure. 
  • PharmaPharma Member, Pharmacist
    From a chemical point of view, they are heat stable.
    Hot processing might however force them into the oil phase and thereby reducing preservation efficacy. Adding enough glycerol or other polyols can (doesn't necessarily have to, though) reduce this drift.
  • Thanks for the responses! I also have something else I’m curious about, somewhat related to cosmetic preservation, I always hear that bacteria need water to thrive, but how is it that when people swatch their used lip balms/lip gloss/lipstick (which are commonly anhydrous) on agar plates, a lot of bacteria grow on the plates after a few days? I see the same thing happen when people swatch used eyeshadow/blush powders, which were not made using any water. I’m wondering if and how bacteria can still survive/grow in cosmetics even without water?
  • PharmaPharma Member, Pharmacist
    They simply stick on the surface awaiting their turn. Many microbes have spores and other long-term survival forms and/or can cope with tiniest amounts of water and nutrients to survive a very long time.
  • PerryPerry Administrator, Professional Chemist
    @Safaazul - you can think of spores as little tiny seeds. They stay dormant until they are put in the right conditions. Then they grow and grow.  This is why you shouldn't share makeup or other beauty products with other people.  It's teaming with your own body's microbial spores.

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