Any ingredients that should not be used with CLAY (kaolin, bentonite)

Hi all

Just wondering if anyone can provide any research articles or personal insights into whether any ingredients should be avoided when a formula has clays (kaolin and/or bentonite - ie for a clay mask).

We've been testing some clay mask formulas, and a small portion of people have had a reaction (red and burning).

I'm wondering if the clays are having a reaction with the preservative ingredients used? We don't get any reports of red/flushing or burning sensation when using the same preservatives in formulas that do not have the clays included. We're using a preservative mixture of Sodium benzoate 0.15%, potassium sorbate 0.1%, sodium dehydroacetate 0.15%, phenoxyethanol 0.3%. Also have EDTA 0.15%, Citric acid 0.15% Which is also present in the formulas without the clay and do not get reports of red/flush or burning. So only seem to get some reports of skin sensitivity when the clay is added.

I cant find any research to suggest anything.

Any suggestions or articles much appreciated.



  • PharmaPharma Member, Pharmacist
    You will have a hard time finding real research paper regarding that.
    Clays contain huge amounts of metals such as iron, adding chelates may not work at 'common' concentrations. How much really needs to be added depends on clay type and quality and would have to be tested.
    Clays bind quite a few ingredients and may thereby rendering them useless. Caprylhydroxamic acid would be such an example.
    Small cationic (pH dependent) but also hydrophobic compounds may also bind to clay which makes clay a fairly hard thing to preserve. Mix that with lecithin and you've got yourself a real tough nut to crack.

    Regarding adverse effects of your product: Might be any of the used preservatives. They are all known for, to a more or less often and/or severe degree, causing burning sensation and/or skin reddening. These effects are pH dependent (except phenoxyethanol) -> what's the pH of your product?
  • Hi @Pharma thanks for your response, PH of the product is ~5.

    Yes, the preservatives used are noted sensitizers, what would be your alternative preservative?

    We use the same preservatives for a moisturizer, serum and cleanser. Generally without issue, so it's a bit of a mystery so far.

  • PharmaPharma Member, Pharmacist
    I wouldn't use clay :smiley: .
    Seriously, I can't tell you what I would use because I haven't given clay-based products much thought.
    You could try figuring out which of the four is the issue and only replace that.
  • Bentonite clay is a known irritant. 

    It is mildly alkaline, that can exacerbate certain skin conditions, strip the acid mantle. It seems that your pH is fine at 5. 
    Did you measure it before or after mixing in the clay? Or immediately after mixing it in? If so I would let it sit and monitor the pH of samples at regular intervals over 24 hours, to see if there is any drift.

    Does the redness happens with the same frequency if you used only Kaolin, or very fine french green clay (which is a montmorillonite of different origin)? Both are lesser irritants than Bentonite, with Kaolin being the more "delicate" one. (Nevertheless, clays are "brutal" ion exchange and absorbing agents, from a chemical point of view).

  • nullafullanullafulla Member
    edited March 2020
    @Pharma clay mask without clay.. we might try that and see if anyone notices :wink:

    @Imosca Thanks for your input! The redness does seem to occur even if the bentonite is omitted. The amount of bentonite is only 3%, Kaolin is 33%. The PH is tested after the formulation has been completed.

    We haven't tested PH at regular intervals though, as we didn't think it would drift too much, but might be worth doing that.

  • PharmaPharma Member, Pharmacist
    @Pharma clay mask without clay.. we might try that and see if anyone notices :wink:
    Who was it again who has a sugar scrub without sugar? As long as your mask looks like a clay mask, you may call it clay mask if you add something which might be interpretable as clay-ish related. :blush:
  • BelassiBelassi Member, PCF student
    It's the bentonite. No question.
    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.
  • Does anyone have a source on bentonite as an irritant? The CIR report from 2016 didn't indicate any dermal irritation or sensitization and CIR is usually my go-to for questionable materials
  • HalimHalim Member
    ı have good experiance on paint and coatings
    do you ever test Laponite RD in your formulation
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