Acid suggestions to lower a skin cream pH while avoiding the sun-sensitizing citric acid?

I need to sharply lower a skin cream pH (to make it more acidic)
but I want to avoid using citric acid as it can make skin more sunburn sensitive
https://www.fda.gov/cosmetics/cosmetic-ingredients/alpha-hydroxy-acids

Any non alpha hidroxy acid suggestions?
I'm leaning heavily towards acetic acid.
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Comments

  • PerryPerry Administrator, Professional Chemist
    Phosphoric acid
    Hydrochloric acid

  • Perry said:
    Phosphoric acid
    Hydrochloric acid

    Is using HCl in cosmetics safe ? 
  • PerryPerry Administrator, Professional Chemist
    @Aziz - well, when diluted out in a formula it's perfectly safe. It's like using NaCl as it dissociates in Cl- and H+ ions.  The less safe part is during production.  But if you are making a batch in a lab you can make a 1% HCl solution and that is fine to use.
  • Perry said:
    @Aziz - well, when diluted out in a formula it's perfectly safe. It's like using NaCl as it dissociates in Cl- and H+ ions.  The less safe part is during production.  But if you are making a batch in a lab you can make a 1% HCl solution and that is fine to use.
    Thanks .
    Can we use it like AHA or BHA in skin care products  or we can use it to adjusting pH  like NaOH ?
  • MarkBroussardMarkBroussard Member, Professional Chemist
    Phytic Acid
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • PerryPerry Administrator, Professional Chemist
    @Aziz - HCl does not work like an AHA or BHA.  It is simply used to adjust the pH of the system in the same way that NaOH is used. It's not meant to do anything else in the formula.

  • I was going to say phytic acid as well, are the AHAs really able to cause sensitization if they are used for pH adjusting at low concentrations? I think I'll try to look for a study on this
  • PharmaPharma Member, Pharmacist
    Regarding phytic acid: be careful because many suppliers selling phytic acid actually sell sodium phytate or calcium/magnesium phytate which won't do the trick.
    I'd say that, unless your product is really acidic and/or requires higher percentages, using any organic acid such as citric, acetic, malic, lactic or whatever to lower pH to +/- neutral won't cause sensitisation. But that's just a guess!
  • My point is

    Wouldn't strong mineral acids like Hydrochloric, phosphoric or sulfuric acids look too harsh on an ingredient label?
    Even if they're used in tiny amounts, some customers who know no better would get scared just by reading that.

    Therefore I'm considering acetic acid which is found in vinegar, which some people apply vinegar on their skin.
    Concentrated acetic acid smells nasty, but we'll see if the finished product does when diluted.
  • ozgirlozgirl Member, PCF student
    What are you using in your cream that it needs that much pH adjustment?
  • Gunther said:
    My point is

    Wouldn't strong mineral acids like Hydrochloric, phosphoric or sulfuric acids look too harsh on an ingredient label?
    Even if they're used in tiny amounts, some customers who know no better would get scared just by reading that.

    Therefore I'm considering acetic acid which is found in vinegar, which some people apply vinegar on their skin.
    Concentrated acetic acid smells nasty, but we'll see if the finished product does when diluted.
    As far as I know vinegar is not recommended for adjusting skin pH . Your first point doesn't make any sense where you claim that citric acid make skin more sun burn sensitive.  What FDA told about AHAs is , when you use these as exfoliating agents and with lower pH or as peelers , it may cause sunburn or photosensitive.  The tiny amount of citric acid will not cause any sunburn . We always use NaOH to adjust pH though it is very harsh . Like NaOH Citric acid or lactic acid will not do anything when you use it as pH adjuster . 
  • BelassiBelassi Member, PCF student
    It is meaningless to class acids or bases as "harsh". When used to adjust pH they form harmless salts. Sodium hydroxide and chlorine, suitably combined, product table salt, a key item in our diet.
    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.
  • Belassi said:
    It is meaningless to class acids or bases as "harsh". When used to adjust pH they form harmless salts. Sodium hydroxide and chlorine, suitably combined, product table salt, a key item in our diet.
    Balassi Sir , this is my point also , it is a neutralization reaction .  
    But in this thread Gunther claimed that if citric acid is used as pH adjuster it will cause Sunburn . Is citric acid really caused ' sunburn sensitive ' as he claimed if it is used as pH adjuster ? 

  • So the cir has a ridiculously long report on glycolic/lactic acid that somewhat relates. Honestly I haven't read all of it but it seems to show that concentration and pH, in addition to the formulation method can prevent/mitigate AHA-related sun damage. 
    Ex:
    "The increase in UV radiation damage associated with AHA pretreatment, therefore, was of such a magnitude that it is easily conceivable that aspects of product formulation could eliminate the effect."

    https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/pr34.pdf
  • @Aziz @Belassi Sodium hydroxide would look nasty on a label.
    Even if harmless, tiny amounts are used, customers would perceive it as harsh.

    So do strong mineral acids.
    Hence my question.
  • How about gluconolactone? 
  • PharmaPharma Member, Pharmacist
    Gluconolactone is not pH active. Gluconic acid would work.
  • @Pharma - Gluconolactone hydrolyzes to gluconic acid in water.  
  • PharmaPharma Member, Pharmacist
    Yes, true, but hydrolysis is slow and it's hence not useful for lowering pH to a given value. It will gradually lower pH during storage.
  • In my experience the hydrolysis takes place within an hour. It is easy enough to begin prepping for formulation by making a stock solution. This is a fairly common albeit expensive acidulant in food and cosmetics. 
  • MarkBroussardMarkBroussard Member, Professional Chemist
    From PubChem regarding Gluconolactone:

    3.2.10    pH

    Freshly prepared aqueous solution has pH of 3.6, changing to 2.5 within 2 hours

    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • Interesting. I tried to reverse engineer Lotion P50 (which is basically gluconolactone, lactic acid, salicylic acid and a couple of useless extracts) and even at 8% in the water it only changed the ph from 7 to around 6. I haven’t checked 2 hours later but now I will.
  • PharmaPharma Member, Pharmacist
    Two hours? Okay, that's faster than I thought! Still, IMHO not practical.
    Also, gluconolactone is in equilibrium with glucuronic acid. Should glucuronic acid get 'used up' (neutralised), new one will form. That's nice in case of an additive but complicates things with regard to maintaining a certain pH. Since we're talking fancy/expensive acids, why not use gluconic acid or the like?
  • Jeez! When comes to Glucono Delta Lactone, I am already an expert! Hahahaha! Oddly enough, what is inexpensive to you (all) is expensive to me, vice versa. I have plenty of GdL at my disposal!

    Heat the solution! Need not rolling boil. Need not very hot. No "heat and hold for 20 minutes" nonsense. Heat it (GdL in water) up and the solution magically turns acidic quickly. Yes, quickly. Very, very quick. No more tens of minutes to hours of waiting. Not even a minute, depending on what you use to heat things up. I nuke mine in microwave or mini jet lighter.

    Don't believe me? Add some base like you would neutralise an acid or use some pH testing thing to 'see' the change. The magic is truly instantaneous. I do not seem to get bored repeatedly watching it as it happens.
  • Interesting. I added it to cold water because it dissolves easily anyway. I will check again. I didn’t even consider it a true acid although it’s a PHA because it’s effect on pH was so minor.
  • Cst4Ms4Tmps4Cst4Ms4Tmps4 Member
    edited November 2019
    @ngarayeva001
    It is very soluble in water! I do not know how soluble it is but I manage to make a solution of it, 60g or 60% in water. I do not know where you live, for me is easy for it to be dissolved due to the high 'room temperature' here.

    Many Asians making (silken) bean curd had long replaced Citric Acid and Boric Acid with GdL. Without scientific data they learnt that it has something to do with heat. Not only it is far less sour than other acids (at the same gramme), but also makes the smoothest and most even bean curd because GdL can be properly mixed in and the soybean milk has chance to rest and stay still while proteins are being coagulated. With Citric Acid the result is nearly instantaneous regardless of temperature, bean curd like this is gritty, uneven, and if 'unlucky' it tends to and prone to oozing liquid (syneresis).

    I presume you tested pH while it is not completely turned to its acid form. GdL is slightly sweet! I do not mean sweet as an expression, it is truly sweet. Taste it! Very soon it turns sour. I assure you, its pH is proper low once its devilish side of metamorphosis is complete. Depending on concentration, it will start to sting your eye, wound, etc. Oh, also depends on concentration, pH is low enough to make your eyes squint and make funny faces. I guess the latter is the best evidence!   :D
  • @Cst4Ms4Tmps4, I'm interested in your experience with Glucono Delta Lactone. Do you then ever use it in place of Citric Acid in skincare? Would it also improve the smoothness of an emulsion in the same way that it does for the bean curd?

    In heating, do you heat the GdL in water separately before adding to the rest of the formula? How hot does it need to be heated to get the nearly instantaneous acidification that you mention?

    Does the pH drift for some time after in a formulation?

    Thank you!
  • Cst4Ms4Tmps4Cst4Ms4Tmps4 Member
    edited November 2020
    @helenhelen

    OMFAG! I missed your comment! I had not been using this site for some time.
    And there is no notification to show me who tags me and who responded to my comment/post. I need to keep the bloody tab/page open! This is the reason why I got bored of this.

    Do you then ever use it in place of Citric Acid in skincare?

    Yes, I use GdL exclusively. I hardly use Citric Acid. I never use other acids. I found that the acid form (Gluconic Acid) is way more 'moisturising' than Citric Acid.
    Moisturising may be a useless terminology (marketing thing). I should say 'smooth'.

    Citric Acid tends to provide 'rough' feel. I presume that is crystal.

    Gluconic Acid does not seem to recrystallise, it becomes sticky instead. This may explain as to why the lack of roughness. Perhaps it was a coincidence. I am not sure; I only did the drying test only one time. I was understood that GdL is an ester. Ester tends to have 'special properties'.

    In other words, I do not use GdL for chelating. It is for feel thing.

    Would it also improve the smoothness of an emulsion in the same way that it does for the bean curd?

    No. It does not make anything smooth like that. LMAO. It is not slippery. It is just another acid stuff.

    In heating, do you heat the GdL in water separately before adding to the rest of the formula? How hot does it need to be heated to get the nearly instantaneous acidification that you mention?

    I heat a solution and see a little water vapour or condensation on beaker wall, and that is all.
    No boiling. I have nothing against 'destroying' ingredients with high heat. Just that it saves my time. The process can be done easily and quickly, no good reason for me to boil it or heat it for hours on end.

    No oil phase water phase. All in one pot. Steps to adding in stuff can be at any sequence. 

    Does the pH drift for some time after in a formulation?

    Whoa, difficult to impossible question to be answered! It depends on what substances are in the mix. Also, depending on the characteristics of the substances. GdL, for instance, seems like nothing on the pH, but it becomes more and more acidic. Many people who do not know better would wonder why pH was only slightly acidic and then very acidic after a while (or quickly if they heat the solution after pH test). Some also wonder why thickened solution or gel miraculously gets destabilised (liquified) after certain minutes or hours (no heating), if they use good old Carbomer.

    I do not follow what cosmetics gurus do. I already had my fair share of being a mindless sheeple. Justified mindlessness as I was starting out so I must not recreate the wheel. First copy what others do and then modify/improve from there. This is the reason why I made a very good product suited for my skin and weather conditions. My friends are using the same thing as I use, and they said they no commercial ones is as good as mine. Not because they are my friends they lick my backside. It is the power of DIY and countless tests. I live in the tropics and most people here are 'oily', lots of substances used and recommended in temperate countries are too heavy or greasy for us. Skin will "sweat" and shine prematurely even if the weather is cool. (What is solid in a temperature climate is actually liquid in a tropical climate due to temperate difference. Coupled with very high relative humidity. Thus, lots of oily stuff are marvellous over there, horrible over here)

    All I need is a bit of understanding of how things works. And some experimentations, of course. Because asking people and not a single test on my side I will never experience what others are saying/doing, I will for ever be asking and guessing, and very likely be following the Dunning-Kruger graph like those natrel-oganik-eko-sustaainibel-respncible activists debating from their arse.
  • @Cst4Ms4Tmps4
    @helenhelen

    OMFAG! I missed your comment! I had not been using this site for some time.
    :D :D :D  OMG my questions were from November 2019 - the world was literally a different place back then!! Thanks so much for your answers - they are very interesting and useful.
    I do not follow what cosmetics gurus do. I already had my fair share of being a mindless sheeple. Justified mindlessness as I was starting out so I must not recreate the wheel. First copy what others do and then modify/improve from there. This is the reason why I made a very good product suited for my skin and weather conditions. My friends are using the same thing as I use, and they said they no commercial ones is as good as mine. Not because they are my friends they lick my backside. It is the power of DIY and countless tests. I live in the tropics and most people here are 'oily', lots of substances used and recommended in temperate countries are too heavy or greasy for us. Skin will "sweat" and shine prematurely even if the weather is cool. (What is solid in a temperature climate is actually liquid in a tropical climate due to temperate difference. Coupled with very high relative humidity. Thus, lots of oily stuff are marvellous over there, horrible over here)
    That's a great mindset. I also believe in that. I'm currently on iteration #130 or thereabouts of one single body cream - that's not an exaggeration. I'm in the opposite climate to you.. I've been working on a product for drier and dehydrated skin. Like you, people have said it works better than any commercial products. But I was never happy with the texture, smell etc.. but am getting very close now to what I had in mind.
  • @helenhelen

    Only now I got that "1" symbol as notification!  :(
    Thankfully not another one year before I notice you wrote to me! Ha!

    I do not count how many tests I did. But I know many, many. I started this DIY stuff since 2017.

    One of my friends lives in the UK. She always complains about skin too dry. It is common over there due to low temperature and relative humidity. I sent her a sample of dreadfully rich lotion (not cream) and it was still not enough for her. I used it here and I sweat unnaturally as mentioned before. That was based on Behentrimonium Methosulphate and Behentrimonium Chloride. Archaic formulation. Hehehe. This was my earliest copy! Copied from SwiftCraftyMonkey. My first exposure to DIY stuff.

    Ah. So, you are also DIY.

    The problem with DIY is we do not always get to use "advanced" stuff. Of course money solves all problems whether DIY or not. I do not have too much money. I am not funded. I already have many useless stuff collecting dust and waiting to be thrown away.

    Useless stuff = marketing

    Generally, I wasted lots of money on marketing. I considered myself paying for a lesson, and lesson learnt!

    Since learning much from this site and people, only will I know there is so much bull and cow in this industry as any other industries in the world.
    I join gardening/horticulture/agriculture groups (research-based, of course) only from there did I know it also has full of woo-woo of its own.

  • @Cst4Ms4Tmps4 Yes, I've been DIY since this year, but the crux of the formulation I'm working on is actually from a chemist I originally paid to develop something. It's the best of both worlds - the decades of experience and know-how from a cosmetic chemist, and then the ignorant DIY dabbling without paying a chemist for every time I want to tweak the formulation or try some new wonder ingredient I just read about. After all these iterations, I have barely strayed from the original formulation, just very tiny tweaks and additions/subtractions, but all the trial and error has made a difference overall.

    I'm afraid I have also spent a lot of money on ingredients that are now collecting dust. But it's all a learning experience! If you didn't try it, you wouldn't know!

    And yes, the UK winter dry air is very unforgiving!
  • Separate "citric acid" question:  Is it ever acceptable to add minute amounts (e.g., 0.05%) of citric acid during the water phase if one knows in advance that the pH will be too high?  (It seems like standard practice is to always test the pH and add citric acid during cool down.). Thank you.
  • suswang8 said:
    Separate "citric acid" question:  Is it ever acceptable to add minute amounts (e.g., 0.05%) of citric acid during the water phase if one knows in advance that the pH will be too high?  (It seems like standard practice is to always test the pH and add citric acid during cool down.). Thank you.
    I do all the time....for some reason I get a little foam on my water phase....and the second I add the citric....foam is gone....love it.

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