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why urea?
In the original tests of hair removal using glycyrrhizic acid, the experimenters dissolved it in a mixture of ethanol and urea.
The ethanol I can understand because it is soluble in ethanol and not in water, but why the urea?I don’t have urea and it isn’t an easy item to obtain here, (I rather think that a bag of fertiliser will not be of cosmetic standard).Suggestions for alternates? What function is the urea doing? -
25 Replies
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Urea is a great moisturizer humectant. It also has keratolytic properties (skin-exfoliating), antiseptic & deodorizing effects. So maybe they using it as a moisturizer and penetration aid. There was a study that tested the penetration enhancing effects of urea with Vitamin A. The website isn’t taking my Universities credentials at the moment so I can’t access the full journal, but it’s on the European PubMed. -
@Belassi Urea is a natural moisturizing factor that is part of the stratum corneum . Moisturizing factors are water soluble compounds, including amino acids, peptides, some organic acids, ions, urea, lactate, citrate, and sodium PCA (I may have forgotten some).
From the strictly moisturizing effect, if I would have to replace urea with something, I would go with either sodium PCA or sodium lactate. If I remember correctly lactate can make skin sensitive to sunlight so you want to limit to no more than 2 or 3%
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Thanks Ruben. Unfortunately I can’t obtain either of those. I suppose I will have to investigate agricultural suppliers. What a nuisance.
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Agricultural grade urea will not be of a suitable standard for cosmetics. It often contains small rocks and dirt.
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@Belassi, can you not get it from a pharmaceutical ingredient supplier?
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Bill, I wouldn’t know where to begin. I don’t think we have such things. There are some basic commodities that I have huge trouble with. For instance I simply cannot find sorbitol in Mexico. I’m sure that cake companies use it but they deny all knowledge of it.
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well Merck are a major European manufacturer of pharma grade urea, and apparently they have a sales office in Mexico:
http://www.merck.com.mx/es/contact/contacto.html
and even if they can’t help you directly, they should be able to point you to a distributor
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Thanks for that, Bill. I’ll pursue that in the morning.
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Yep. Sent an email. I’m going to begin parallel developments with these raw materials. I found a few examples in forums of people who had tried it by duplicating the original experiment and I noticed that they all reported a remarkable improvement in their skin condition. So my first step will be to test solubility in a wide range of possibles, e.g. squalene, DMSO, hot glycerol distearate, propylene glycol, and so on. Then I’ll be able to think about the best carriers for it.
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Is urea not a skin irritant?
Or is there a threshold % where it is okay?
I have always dreaded touching this ingredient, maybe it’s an overreaction on my part. -
There appears to be quite a few skin creams based on urea. However I am only going to use it in the initial tests of the hair removal system.
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I know this joke is getting old, but maybe it’s time for camel urine
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Yes, Urea can be a skin irritant at high concentrations, but at anything less than 5% should not be a problem
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The formula is given as 15% gl. acid, 20% ethanol and 10% urea, water q/s (55%).
Preparation at 80C, I assume due to solubility issues. -
I managed to locate a new supplier in my city using quiminet. It’s a lab supplier and so the urea is reagent grade, $60 a kilo! Ouch. Still, I bought half a kilo because that will be enough to make 5Kg of test materials, adequate I think for the opening investigative phase. Usefully I also found they had genuine Pyrex beakers so I restocked my glassware. The Pyrex beakers are much thicker, far more robust than the Kimex ones, and as for Chinese glassware … don’t! It’s too fragile.
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I’d love to hear from anyone who has used urea. So far my research indicates that it tends to raise pH by 2 points, and also that it produces a smell of ammonia due to its tendency to decompose. But it certainly looks to have some interesting skin properties.
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I haven’t experimented/used that much with urea, but it’s super* sticky/tacky like glycerin can be.
*Okay, I might have to admit I have very low tolerance for stickiness/tackiness, but other people I know have complained about it too.
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I use Urea in one of my formulations … it has excellent moisturizing properties and is part of the skin’s Natural Moisturizing Factor. I have seen formulations where it was used as high as 15%, but it can be an irritant at high concentrations. I haven’t noticed anything unpleasant about using it (but then, I pee in my pants, so maybe I don’t notice the smell)I can only surmise that the Urea in formulation you are considering may be as a penetration enhancer for the GL Acid? Perhaps that level of GL Acid is irritating and/or drying to the skin and the Urea is included to balance it out?Curious if the authors of the study specified the mechanism of action of the GL Acid on the hair follicles or hair growth?
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I understand that urea can raise the typical pH of a solution by 2 points so perhaps the urea is acting to neutralise the Gl acid and as you say, act as a penetration enhancer.
I should be getting the delivery today so lots of work to do.Thanks for the useful info! I had no idea it would be a sticky substance to use. -
I just tested a 10% solution on myself. It wasn’t sticky and there was no ammonia smell. It was very moisturising, visible improvement in skin texture.
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Continuing with lab tests. The 10% solution shows no sign of degrading, no ammonia smell. PH = 5.5 in solution. I added sufficient 18% NaOH to raise the pH to 9, and there was still no sign of ammonia, which surprised me because if I tried that with, say, ALS, I would definitely have got ammonia. So it appears to me that urea is reasonably stable.
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Are you sure that GL acid stands for glycyrrhizic acid and not glycolic acid? The latter would make a lot more sense to me.
Besides, urea indirectly raises the measured pH of certain solutions. Chemically speaking, it’s neutral (depending on purity slightly acid as you’ve seen yourself) but causes weak acids to dissociate stronger (if it does so with weak bases I do not know). This means, the pH changes are rather unpredictable and depend on the mixture.
Besides, you’re in Mexico, right? Maybe you get luckier when asking for ‘carbamida’
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It has several beneficial effects such as moisturising which is the reason why it’s commonly used in pharmaceutical preparations (and at higher concentrations often with salicylic, lactic, and/or glycolic acid together as exfoliant and keratolytic). It’s part of the natural moisturising factor and you could replace it with other hygroscopic compounds and compatible solutes such as glycerine or PCA. It’s also what makes your kidneys work the way they do and it’s very safe to use and very cheap (usually); you could, in moderate amounts, eat it without any issues. Besides that, it’s a chaotropic substance, it disturbs order (one reason for it’s penetration enhancing and keratolytic activities). Therefore, it breaks emulsions at high concentrations and isn’t the best friend of vesicles either. Depending on the exact reason why it’s in your preparation, you certainly should be able to replace it with something else but honestly, it’s a really cool stuff
and as long as I don’t know what your GL acid really stands for… -
glycyrrhizic acid is definitely what I have stuck in the damn customs right now… one of the first tests will be stability testing to check for pH change, right enough!
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@Belassi
I got struck by uncertainty and did look it up: Really, there’s this 2014 study conducted on lab rats about glycyrrhizic acid for hair removal.
I only heard about anecdotal use of it for the opposite… thanks for letting me learn something new today!
Now that I know what GL acid stands for: It’s a pretty big molecule, a triterpene saponin, bearing three potential negative charges and two sugars. What does that mean? It is a natural ‘soap’, an anionic surfactant, but it needs either a high pH to form micelles or alcohol for a reasonably well solubility. Similar molecules are usually very poorly resorbed and can’t penetrate the skin either. But glycyrrhizic acid has an affinity for cholesterol-like molecules and dissolves in or mixes with sebum and I can imagine (more of an educated guess than a mere fantasy) that it therein diffuses for example to the hair follicles. Adding ethanol and urea will soften and ‘liquefy’ said cutaneous sebum allowing for a faster diffusion and deeper penetration along the hair shafts. Besides, urea in solution becomes a pretty good solvent itself, similar to DMSO. As I already mentioned before, urea especially together with ethanol should counteract the tendency of glycyrrizic acid to build micelles but form a true solution instead. Once the alcohol evaporates, solubility drops, and it’s forced into the skin’s lipid film. Were you to use plain water, then it should form micelles; upon evaporation, these are less likely to ‘bond’ with sebum and therefore might just sit on your skin, doing nothing except waiting until you take the next shower. And that’s why I guess the proposed concoction is not only super simple but also efficient and astonishingly nifty. -
Way cool! Yes, you found the same abstract that gave me this idea. I also found one more item; in a transexual forum. A man transiting to female also found the same study, formulated it, and used it successfully. Great analysis, many thanks for that, it makes sense. I do intend trying the original simple formula first of all.
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