Lactic acid in deodorant... Need help to understand

hello, if you please would help me about this. 
I formulated deodorant as following:

Cetostearyl alcohol 5 %
Viscolam AT 100p     2% emulsifier 
 (inci;
Sodium Polyacryloyldimethyl Taurate, Hydrogenated Polydecene, Trideceth-10) 
Carrageenan 0.2 %
Oils 6%
Sorbitol 2%
Edta 0.1
Zinc oxide 5%
Zinc ricinoleate 3%
Kaolin 5%
Corn starch 2%
Licorice  extract 5%
Aloe vera extract 1%
Vit.E 0.5 %
Preservative 0. 5%
Fragrance 1%
Water up to 100

The consistency of the cream is good and it's spreading over skin. 
But, I found the ph about 9. I used lactic acid to lower it. 
I added 3% lactic acid, ph now 7.1
I still need to lower it to 5.5 but idk if high percent of lactic acid would be irritant for the underarm ? Do i need to add sodium lactate with it? 
And is the kaolin & zinc oxide causing that high ph?



Comments

  • BelassiBelassi Member
    Licorice  extract 5% - that is a huge amount. What kind of extract is that?
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  • AmiraAmira Member
    @Belassi ;
    It is a water based extract  
  • Bill_TogeBill_Toge Member, Professional Chemist
    the zinc oxide is reacting with the acid, which is why you're needing to use a lot of it - I'd suggest removing the zinc oxide
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • AmiraAmira Member
    @Bill_Toge ;
    Zinc oxide is active ingredient for its antimicrobial effect and reducing odor. 
    If i use citric acid to lower ph, is it still react with zinc oxide? 
  • Bill_TogeBill_Toge Member, Professional Chemist
    Amira said:
    @Bill_Toge ;
    Zinc oxide is active ingredient for its antimicrobial effect and reducing odor. 
    If i use citric acid to lower ph, is it still react with zinc oxide? 

    zinc ricinoleate (already in the formula) will do that job a lot better
    with zinc oxide, the same thing will happen with any acid
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • AmiraAmira Member
    @Bill_Toge ;
    Thank you. I will try the formula without zinc oxide. That's supposed to lower ph. 
  • AmiraAmira Member
    Belassi said:
    Licorice  extract 5% - that is a huge amount. What kind of extract is that?
    It is 70 % water extract as I  told by the supplier 
  • BelassiBelassi Member
    The thing is, licorice is not very soluble. The pure acid is about 0.2% soluble. I buy a powdered root extract, direct from China. It is a yellow-brown powder with 12% of the licorice acid active ingredient and reasonably soluble because it also contains saponins. Frankly, any liquid licorice extract you buy is likely to contain a risible amount. I use 0.2% of the 12% powder in shampoo, and it is plenty.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • AmiraAmira Member
    @Belassi ;
    Now, i am willing to remove zinc oxide, lower licorice extract may be to 2%. 
    But as a thought, if i used niacinamide (for underarm  depigmentation along with the licorice extract) and i used  lactic acid to adjust ph to 5.5
    Would it be right? 
  • BelassiBelassi Member
    You won't see any skin lightening effect with that kind of licorice extract, at least I don't think so.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • AmiraAmira Member
    Belassi said:
    You won't see any skin lightening effect with that kind of licorice extract, at least I don't think so.


    Would you please expalin to me why? 
  • BelassiBelassi Member
    Because we have already tried it, with far higher (twenty-fold) concentrations than what you are using. And it didn't work.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • AmiraAmira Member
    @Belassi ;
    Ok, thank you for this. 
    But, what would you recommend for lightening effect (no for vit c, kojic for oxidation & high ph problems) 
  • BelassiBelassi Member
    edited June 26
    We had good results using organic shea butter in a hand cream (noticeable after about three weeks use) presumably due to the vitamin A precursors. But that is no good for your application. You could try potassium glycyrrhizate (the soluble salt of the pure acid) - I make that sometimes by reacting the pure acid (from China of course) with potassium hydroxide. But, it is a salt and can be destabilised by various things including certain preservatives (eg dehydroacetic acid). 
    I agree about vitamin C, even the very expensive palmitate, Aprecier, oxidised in an airless container despite my best efforts and endless reading of patents.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • AmiraAmira Member
    @Belassi ;
    Unfortunately, Potassium glycyrrhizate is not available here nor the acid. I would leave the idea of lightening effect for now. 
    Thank you so much for your input and the information. 


  • BelassiBelassi Member
    I know, it's hard to get hold of. I bought mine from China via mail order. Everyone here in the post service seems to think it's just fine for people to be ordering kilograms of white powder from China!
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
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