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Salycilic acid shampoo
I’m thinking of designing a 2% SA shampoo. What solubiliser though? Is SA soluble in surfactants (eg CAPB, ALS)? Add sodium citrate? If so, how much?
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31 Replies
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From another thread about AS, Betaine was found to increase the solubility of
salicylic acid to 5 % -
SA is soluble in surfactants (at last based on my tests SLES+CAPB)
The problem you may face as well is, if SA is added as powder in the shampoo, it will increase the viscosity and foam will appear.
Have you planned any pH range for the shampoo? I increased the pH to 5-5.5. -
salicylic acid is soluble in surfactant solutions - you’ll have to heat it up to dissolve it, though, and it does take its time dissolving
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Good, thanks for the info. I use hot process normally - the actives content in Plantaren APB is high, and makes it difficult to dilute in cold process. I was thinking of a pH of 4.5
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There are different solubilizers for Salicylic Acid even for only water based formulas. The key factor is whether it will dissolve completely or it will separate after some hours. After dissolving it, you may leave it stagnant for some hours. If it separates/precipitates, you may need to change the technique or solubilizer (type or percentage) You may dissolve it in Glycereth-18 Ethylhexanoate (and) Glycereth-18. The Ratio here is Salicylic Acid : Hest G - 18 -O is 20 : 80 or 2:8 in case of using 2% Salicylic Acid, as shown in the following link, . Actually, you may combine two formulas together. Dissolving Salicylic Acid, then, making the shampoo. Re:
https://www.ulprospector.com/documents/1113931.pdf?bs=605&b=186849&st=1&sl=58775328&crit=a2V5d29yZDpbU0FMSUNZTElDIEFDSUQgRk9STVVMQVRJT05d&k=SALICYLIC|ACID|FORMULATION&r=na&ind=personalcare
https://www.ulprospector.com/documents/1182822.pdf?bs=605&b=238242&st=1&r=na&ind=personalcare
For dissolving Salicylic Acid in Surfactants, I passed by a supporting formula for it:
http://www.stepan.com/uploadedFiles/Literature_and_Downloads/Formulations/Cleansers_(liquid_soaps,_facial_and_bath_products)/StepanFormulation1072.pdfAlso, Salicylic Acid can be dissolved in Ethyl Alcohol (SDA 40) or Denatured Alcohol in different Ratios. But the issues here is flammability (it shouldn’t be heated) and the odor. Strong Fragrance should be added.
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I don’t have access to specialist chemicals so unless I can do it with commonly available items I can’t make it.
I just tried an experimental batch with 2.5% SA in it. Can’t tell at the moment if it will be clear because I have to wait for the bubbles to clear, but it looks hopeful.
The thing is, I measured the pH as 3.2; adding more citric acid failed to change the pH so I stopped adding citric because I assume it’s just buffering and changing the acid into a salicylate.
Is a pH of 3.2 acceptable?
EDIT:
I just realised what I did!!!! Usually I have to add citric acid but this time I should have added NaOH to adjust the pH. Oh well. I will try that a bit later … commercial brands seem to include sodium citrate so there will be some of that in it for sure. -
Test formula:
Plantaren APB 20%
CAPB 5%
Salicylic acid 2.5%
pH adjustment q/s
EDTA 0.2%
Sodium benzoate 0.4%
Lavender EO 0.2%
Peppermint EO 0.1%
Sage EO 0.1%
Tea Tree EO 0.1%
Water Q/S 100% -
Adjusted the pH to 4.0 using NaOH. Acceptable?
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+ 1 hour: It cleared just fine, but did throw a very small amount of precipitate. I guess that I should be able to fix that by increasing the percentage of surfactant or decreasing the percentage of SA; this was a 2.5% trial, so 2% should fix it with a bit of luck.
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Just a thought, instead of changing your base formula try to solublise it with a glycol.
Might be silly, but they way I see it your goal is to incorporate SA into a formula, not building a system around the SA.
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@Belassi I am not sure if this might be of any help but I have noticed in my lab that sodium cocoamphoacetate has been a very good surfactant for some of the worst insolubles in my formulations. Case in point chlorhexidine gluconate which just was a very stubborn component and always kept falling out of the solution. It was completely tamed by this amphoteric, still unsure if this could help you in anyway.
Good luck though on your trials and we shall wait for your updates. -
salicylic acid works best between pH 3 and 4 - if the pH is lower than 3, your product would be classified as a skin and eye irritant
also, adding citric acid has little if any effect because there is already a large amount of a much stronger acid present
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https://www.makingcosmetics.com/Salicylic-Acid-Solution_p_1123.html
Have a look at this link. You can make something similar. -
Thanks, but that is a USA supplier, it would be too expensive to import.
Anyway, this formula is successful. The small cloud has cleared overnight, it is perfectly clear. I tried it this morning and the sensorials are excellent; although now, the viscosity is too low. I will check the pH and adjust if necessary. I see that commercial ones use sodium citrate, presumably as a buffer. I can’t buy that here but I can synthesise either potassium or sodium citrate easily enough. -
Update: Yes the pH had drifted a bit. After readjusting it the viscosity improved. I think I will continue the design but I will reduce the SA content to 2%.
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I told you that after adding AS, foam will be formed.
The link I provided was to have an idea and even make something similar. -
Foam? I hope so! If I am making a shampoo I expect foam. Actually the test shampoo cleared more quickly than the others.
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If foam is created during the process of making the shampoo, in my opinion is a problem.
1. you can’t see if you are getting the result you want in terms of appearance (if everything is dissolved)
2. you can’t check the viscosity
3. Time is wasted for the foam to disappear
It is possible to incorporate SA in the shampoo and avoid foam 100%
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I don’t know if it’s already mentioned, but I use trimethylglycine (betaine) as a solubilizing aid for both salicylic acid and allantoin. Also a big plus: betaine is great for the skin. I haven’t used it in combination with surfactants yet.
I use 1.5-2% of betaine with 2% salicylic acid and I haven’t had any precipitation problems anymore (I also no longer use sodium citrate).
I’ve also used 1.5% betaine with 1.5% allantoin, it works great! -
For Salicylic Acid Separation, try to monitor Stability Results: If the product is OTC or if it has API like Salicylic Acid, you may run Stability Studies . Usually The Stability Studies are Long Term (3 years in case of OTC - 25C), Accelerated (3 - 6 Months - 40C), Intermediate (1.5 Year - 30C), Refrigerated (3-6 months - 6C), Freezer (3-6 Months - below 0C), and UV (3-6 Months-One sample covered by foil and the other without foil with exposing the one without foil to sunlight). With me, I didn’t experience any separation with SLS, SLES, Chembetaine, and Alcohol. But you can run Stability Studies to make sure of that. Also, if you have access to inside or outside lab to test the product for Regression Analysis on Monthly Basis to see whether the Concentration of Salicylic Acid is declining by time. If it’s declining, it could be an indication of several factors: e.g Separation, Cross-Reaction, or other factors. Also, if you get haziness at leat through 3 - 6 Months in the Accelerated Results or precipitation in the Refrigerated or Frozen Results, you may change the solubilizer, technique, or concentration of the solubilizer.
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For Stability Studies, the min. submission for the Long Term should be 1 year and for retesting, it can extend up to 3 years. Also, for refrigeration and freezer, it can extend up to 1 year. If you can make the freezing down to -25C, it can be better. These are just Guidelines but it may vary from manufacturing to another in Personal care and OTC products
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@Belassi
Maybe this is an interesting document. It’s about trimethylglycine (betain) which I mentioned, for solubilizing salicylic acid and allantoin. -
Interesting, thanks; but no use for me since I cannot buy that here.
However the formula I used has been perfectly stable so far, I have no problems with it. -
Regarding my post on March 19, for OTC which includes API, they should be Pharmaceuticals, therefore, I refer to the FDA Stability Studies for Pharmaceuticals:
https://www.fda.gov/downloads/drugs/guidances/ucm073369.pdf
But, it’s non - binding recommendation
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Ketoconazole 2%
Salicylic acid 2%
this shampoo is running good in india for dandruff.Any idea?
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