Antiseptic foaming solution

Hello everyone.
I am formulating antiseptic foaming solution that contains hexamidine, chlorhexidine and p-cresol.
The solution is colorless and clear after preparing. However, it turned red and precipitated after after 2 days.

Can anyone help me? 

I use propylene glycol to dissolve P-cresol and hexamidine.

 Is it possible to use ethylene glycol to dissolve hexamidine and -cresol

I use Hydroxy Ethyl Cellulose to increase solution thickness.
I use cetrimide and tween-20 as soap base

I didn't use anionic surfactant because of antiseptics incompatibility with anionic surfactant.

Any suggestions?
Thank you very much.


  • @Batoul I'd make more tests, removing each ingredient to find out which one is causing trouble. The one I'd start with is p-cresol, since it's one that could give that red color.
  • BatoulBatoul Member
    Thanks @ketchito
    I tried to remove ingredients and found that formula without hexamidine didn't turned red.
    The problem is I need to keep hexamidine since it is one of the active ingredients.
    I have to find out what are the supposed reasons that could likely turn hexamidine red.

    Do you have any suggestions to help?
  • @Batoul Can you do another test, keeping the hexamide and removing one of the other ingredients? This could help you find the one hexamide is reacting with. After that, it'd be good to check if pH change prevents this reaction, so I'd use either a more acid or basic solution to see if that helps.
  • BatoulBatoul Member
    Thank you very much
    I will test it this way.

  • PhilGeisPhilGeis Member, Professional formulator
    Why do you need Hexamidine?  You've got two others
  • Hexamidine could be reacting with your Chlorhexidine. What are the percentages of each of the actives used in this formulation? Chlorhexidine is very sensitive to many other ingredients and using it will require you carefully consider the percentage concentration as compared to the other ingredients in the formulation
  • BatoulBatoul Member
    I use
     0.1% chlorhexidine 
     0.1% hexamidine
    I add them separately.
    Chlorhexidine is added early to the mixture
    Hexamidine is added as lastly.
  • Kindly increase the percentage of the Chlorhexidine to 0.2%. Take out the Hexamidine totally from the formulation. Chlorhexidine is enough for your antispetic property in the formulation. I do hope this help resolve your problem.
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