Optimizing shampoo formula for preservative efficacy


SCI 5%
coco betaine 4.5%
cationic guar gum .35%
guar gum .2% 
xanthan gum .5% 
sodium phytate
benzyl alcohol + DHA 0.8% 

Is there anything else I can do to this formula to help preservative efficacy/reduce bug food?

should i eliminate the cationic guar gum ? as well as regular guar gum? 

ive already reduced my surfactant percentage. it affects foam a lot but i dont mind, and it works for my fussy skin type. 

thanks! 

Comments

  • PharmaPharma Member, Pharmacist
    As a rule of thumbs, cationic polymers are actually helping with preservation, so does a higher percentage of surfactants. Just saying...
  • edited April 4
    @Pharma gotcha! even coco betaine (with water as part of it) helps with preservation? 

    just a bit confusing because some others here have said “if you want to boost preservative, reduce your surfactants, powders, starches, proteins, etc.”
  • PharmaPharma Member, Pharmacist
    Some preservatives are neutralised by surfactants ;) . However, if you add enough surfactant, then they get self-preserving to a degree (that's, as usual, just a rule of thumbs, not a general law). Not that this will be enough on itself but a shampoo likely contains too much surfactants for any surfactant-sensitive preservative anyway. In your case, it might be less dramatic as you don't use PEG-based ones which are said to be the worst inactivators.
    And yes, reduce 'powders', starches, proteins and other bug food. But that only works if you have a working preservative system in the first place. The more food you add, the harder it gets to keep bugs at bay.
  • AbdullahAbdullah Member
    Increase your preservative amount to maximum allowance
  • PhilGeisPhilGeis Member, Professional formulator
    Pharma said:
    Some preservatives are neutralised by surfactants ;) . However, if you add enough surfactant, then they get self-preserving to a degree (that's, as usual, just a rule of thumbs, not a general law). Not that this will be enough on itself but a shampoo likely contains too much surfactants for any surfactant-sensitive preservative anyway. In your case, it might be less dramatic as you don't use PEG-based ones which are said to be the worst inactivators.
    And yes, reduce 'powders', starches, proteins and other bug food. But that only works if you have a working preservative system in the first place. The more food you add, the harder it gets to keep bugs at bay.
    Caution  re.  surfactant in typical shampoo as self preserving.  You'd need about 70% - so might work for a concentrated raw material.  
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