We know which humectants are great, now what?
We've compared how well individual humectants can increase the moisture in our Humectants Comparison Study. We've learned that Glycerin increases skin hydration significantly, and we've also seen Acetamidoethoxyethanol's potentially even higher results. Unfortunately, most results from other humectants were lackluster, some even dismal as they showed hydration even lower than the baseline. In this study, we're exploring how our top-performing humectants behave when mixed with other humectants.
Experiment #1: Glycerin + Acetamidoethoxyethanol
Glycerin
Glycerin is probably one of our favourite humectants as it really does wonders to the skin. Because it is a small polar molecule like Urea, it can replace water between the lamellar layers to keep them more fluid under dry conditions. [1][2] Aside from that, Glycerin and other small polar molecules change the conformation of keratin fibers to resemble their softer elongated form even in dry conditions. [3] To know more about how humectants make your skin soft, check out our previous Lab Note on it here:
The mechanical function of Glycerin in skin hydration isn't really the main reason it is an incredible ingredient. Technically other small polar molecules like NMFs can also interdigitate with the lamellar layers and bind and soften keratin fibers (albeit at a lower rate). What makes Glycerin stand out is its effect on the lipid biosynthetic pathway.
Living keratinocytes have water channels called Aquaporins that serve as shortcuts for water to hydrate the upper parts of the skin. Newer research found that aside from water, specific subsets of Aquaporins (Aquaporin 3) also transport Glycerin (in addition to water) to the upper layers of the skin. Hence their fitting name: Aquaglyceroporin. However, the end result of having more Glycerin in the upper layers isn't really the main event. Interestingly, transporting Glycerin through the Aquaporin3 channels signals various biochemical pathways such as lipid production and wound healing. [4] [5] This is why applying Glycerin isn't just for skin hydration but also barrier repair.
Acetamidoethoxyethanol (Elfamoist AC)
This is a relatively new ingredient that doesn't have any published articles written about it yet. The only information we have for it are the ones provided by the manufacturer and the safety assessment report by NICNAS. Honestly, this ingredient has been sitting unopened on our R&D shelf for about two years. We only added it last minute to the humectants we tested for the previous study.
According to the brochure, it exceeded Glycerin in its ability to increase hydration as measured by Corneometer. They tested a bunch of humectants, including Glycerin, Betaine, Sodium PCA, Glyceryl Glucoside etc. Acetamidoethoxyethanol came first, with Glycerin second and Betaine third. Further behind is Sodium PCA. We take manufacturer brochures with a grain of salt, but our results confirmed their findings. We did a double-take as we thought it was an instrument error, but a retest confirmed the results.
The manufacturers also studied its ability to hydrate several layers of the skin by ATR-FTIR (Attenuated Total Reflectance- Fourier Transformed Infrared Imaging Spectroscopy). It showed that it hydrates the whole Stratum Corneum and keeps it hydrated for up to 30 hours. Using the same instrument, they also studied its potential effects on the lamellar layers of the skin barrier. The results show that it doesn't affect the organization of lamellar lipids.
NICNAS (National Industrial Chemicals Notification and Assessment Scheme) in Australia also assessed its safety, and they concluded that it is non-irritating, non-sensitizing, and non-mutagenic.[6] To top it all off, it is stable, non-sticky and imparts a great feel on the skin.
Purpose:
We aim to assess combinations of Glycerin and Acetamidoethoxyethanol regarding their ability to hydrate the skin. Our secondary goal is to assess the feel of the combinations.
Procedure:
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions tested
Results:
Increasing Elfamoist from 5% to 10% led to a more significant increase in hydration than when it is in equal percentage with Glycerin. It would have been more insightful if we added one more solution of 10% Glycerin + 5% Acetamidoethoxyethanol. However, realistically we wouldn't use such a combination as Acetamidoethoxyethanol is less sticky than Glycerin. We then tried to push the limits of how much we could increase Glycerin in the solution. Increasing Glycerin to 10% led to another significant step in skin hydration.
Interestingly, 10% Glycerin + 10% Acetamidoethoxyethanol was less sticky than 5% Glycerin alone. It seems that Acetamidoethoxyethanol improves the solution's texture even if a high amount of Glycerin is present.
Experiment # 2: Hydroxyethyl Urea
Hydroxyethyl Urea
Hydroxyethyl Urea is a derivative of Urea, with ethanol added to the amino group. It is a great humectant but not as great as Glycerin. However, it trumps all humectants in terms of skin feel. It is very liquidy, and it just feels like water. Another advantage is that it is not as irritating as Urea. Because we are dealing with humectants that can act as barrier looseners, Hydroxyethyl Urea is a better choice as it is milder. On the downside, it doesn't have the exfoliation power of Urea. Both Urea and Hydroxyethyl Urea are pH-sensitive; the more acidic the solution is, the more degradation you will see. Based on our previous experiments, Hydroxyethyl Urea is more stable compared to Urea, and at the same time, it is easier to stabilize. A buffer system would always be needed when formulating with Urea or Hydroxyethyl Urea.
One very cool feature of Hydroxyethyl Urea is its synergy with other Humectants. Aside from the added hydration added to the solution, it also lessens or removes tackiness from Glycerin and other humectants. This allows us to use more heavy-lifters, whereas usually, we can only use them up to 5%. For this experiment, we assess its effect in combination with Glycerin and Acetamidoethoxyethanol. Interestingly, Acetamidoethoxyethanol and Hydroxyethyl Urea are both manufactured by the same company (Nouryon)
Purpose:
We aim to assess how Hydroxyethyl Urea works with Glycerin+Acetamidoethoxyethanol regarding their ability to hydrate the skin. Our secondary goal is to assess the feel of the combinations. As we go along, we assess not only their effect on hydration but as well as their skin feel. It doesn't matter how hydrating one ingredient is; if it is super tacky, no one would want to apply it on their face.
One thing to note is that the "carrier" solution isn't a perfect control. Previously, we've tested individual humectants, so the carrier is water. However, in this series, our goal is to find the best possible combination of humectants, starting with the best performers. This means that it gets harder and harder for subsequent humectants to cause significant change because the carrier gets increasingly hydrating. We did this on purpose to weed out unnecessary humectants.
Procedure:
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions tested
Results:
Hydroxyethyl Urea shows a dose-dependent increase in hydration. As you see from the graph, 5% Hydroxyethyl Urea is almost significantly different from the carrier solution. However, we would still consider it as not significant. 10%, on the other hand, is significantly different than the carrier solution. 10% is the max we can use for leave-on, so we didn't test any further concentrations.
The skin feel is surprising and a bit perplexing. At 5%, the feel was worse than the carrier. The spreadability and slipperiness decreased, and it was a little tacky. However, when the Hydroxyethyl Urea was increased to 10%, the feel improved significantly compared to the carrier solution.
Experiment #3: Hyaluronic Acid Crosspolymer
Hylauronic acid Crosspolymer is a modified version of Hyaluronic acid (HA). HA can vary in size from ultra-small molecular weight of 5000 Daltons (atomic mass unit) to 3 Million Dalton in size. The most commonly used HA in skincare is around 1 Million. Hyaluronic acid crosspolymer links together High Molecular weight HA (1M above) to form a polymer of infinite Dalton size. The resulting polymer has a different feel and benefit to the skin than standard Hyaluronic acid. It is 50X more hydrating than 1M Hyaluronic acid with the added benefit of antioxidant effect. (Although that's just a manufacturer claim)
Purpose:
This experiment aims to assess the effect of Hyaluronic acid Crosspolymer on Skin Hydration.
Procedure:
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions Tested:
Results:
As the graph shows, 5% didn't do anything for hydration. At 10%, there is some hydration, but it is not significant from the carrier (Sample 1)—another disappointing result by HA.
With regards to feel, this is the only solution (so far) that had a great feel, perfect spreadability and slipperiness with a matte finish. Too bad it didn't perform as well.
(Note: we tested HA in a separate experiment, results will be posted on its own lab note.)
Experiment #4: Aquaxyl (Xylitol, Xylitylglucoside, Anhydroxylitol)
This is an exciting ingredient for us. In essence, it is a combination of polysaccharide derivatives (Xylitol, Xylitylglucoside, and Anhydroxylitol) that forms a layer on top of the skin. It claims to boost the production of Ceramides, Filaggrin, Aquaporin, Tight Junctions, and so much more. Honestly, it is probably the boldest claim we've ever seen made by an ingredient.
As we dig deep into the individual components of Aquaxyl, there are actually some great studies written on the individual ingredients and their combination. At 15%, Xylitol lowered irritation from SLS, but not as statistically significant as 9% Glycerin (This is why Tabula Rasa has 10% Glycerin). [7] Interestingly, in-vitro results show that both Glycerin and Xylitol upregulate Filaggrin, Loricrin, Involucrin and Occludin, with Xylitol showing more pronounced effect than Glycerin.[8] 5% Xylitol decreased TEWL, increased the level of Filaggrin in-vivo (biopsy), but was unable to change the level of MMP. [9] Aquaxyl has a lot of potential, and we sure will write an encyclopedia entry for it. However, one drawback is its texture. It is as thick as honey, and the texture is tacky and draggy. You can't use it at the percentages mentioned in these journals.
Purpose
This experiment aims to assess the effect of Aquaxyl on Skin Hydration.
Procedure
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions Tested
Results
Aquaxyl has a significant difference in immediate skin hydration compared to carrier solution. Even at 1%, it showed quite a bit of a jump. Based on our findings, it doesn't seem to have a dose-dependent effect. In our previous study, Aquaxyl didn't perform well as a single ingredient in a solution. The results here agree with previous journals where they suggested that it has a synergistic effect with Glycerin. In several other journals, it can decrease TEWL to increase skin hydration. (We have no doubt about that. With that kind of texture, it would be more surprising if it didn't change TEWL)
In terms of skin feel, it is pretty interesting. At 1%, it improved the spreadability and slipperiness of the solution. However, at 3%, the spreadability decreased, and the slipperiness decreased by a lot. To add to that, it started to be slightly draggy. 5% was plain horrible.
Experiment #5: D-Panthenol
Panthenol or Provitamin B5 has two optical isomers: D-Panthenol and L-Panthenol. It is water-soluble and readily penetrates the skin; it can even increase the penetration of actives. Panthenol is a widely studied ingredient that affects lipid synthesis, hydration, wound healing, and anti-irritation. [10]
- Barrier Repair: Once it converts to Panthothenic acid, it serves as a co-factor to coenzyme A, which acts in fatty acid synthesis and gluconeogenesis.
- Wound Healing: Panthenol promotes Fibroblast proliferation and Epidermal re-epithelialization which makes it excellent for wound healing
- Hydration: It is hygroscopic and adds to hydration but it is found to enhance the hydration effect of Glycerin.
- Anti-irritation: It’s been shown to decrease irritation due to SLS and Retinol. It was able to reduce warming, stinging, itching, and tingling, making it an excellent soothing agent.
Note: D-Panthenol or Dexpanthenol is the more biologically active form, while the DL-Panthenol (also used in skincare) is only 50% active.
Purpose
This experiment aims to assess the effect of Aquaxyl on Skin Hydration.
Procedure:
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Samples Tested
Results
Panthenol didn’t show any immediate hydration effect even at 5%. We think its hydration effect is more seen in the long term as it improves the moisture barrier.
As for the skin feel, at 1%, the spreadability and slipperiness decreased. At 3%, the slipperiness and spreadability decreased significantly, and the drag was noticeable. At 5%, the drag was not pleasant, and the spreadability and slipperiness were decreased even more.
Experiment #6: Betaine
Betaine is one of our favourite humectants here at Regimenlab. In nature, it is an osmolyte present in plants where it serves as an anti-desiccant. It has excellent hydrating, that's why we use it in some of our products. In our previous humectant study, Betaine got 3rd place, following Acetamidoethoxyethanol and Glycerin. One interesting thing about Betaine is its ability to increase loosely-held water in the skin. If you look at its structure, it looks like a helicopter. Those quadruple Carbon attached to a central Nitrogen is rotating freely. This pushes out any water that is hydrogen-bonded to the oxygen molecules. This mechanism increases the available loosely-held water percentage in the Stratum Corneum where it is needed the most. (Remember: barrier repair enzymes and other enzymes are water-dependent enzymes. They can't crawl on a desert).
Aside from its hydrating effects, it also has anti-irritant and anti-inflammatory effects. It is also used in toothpaste to prevent gum irritation. It also serves as a buffering agent in the skin, preventing any increase in pH, leading to Barrier damage. Learn more about Betaine in our Skincare Encyclopedia.
Purpose
This experiment aims to assess the hydration effect of Betaine in combination with other humectants.
Procedure
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions Tested
Results
Betaine showed a dose-dependent increase in hydration up to 3.5% and plateaued afterward. It almost showed statistical significance at 3.5%, but it is nonetheless non-significant. Keep in mind that it gets really hard to increase hydration at this stage because it is close to maxing out. 
Regarding the skin-feel, Betaine didn't really affect slipperiness and spreadability. The only thing it imparted was a matte, powdery feel. Only at 5% did the Spreadability and Slipperiness change, and the chalky feel + drag was apparent.
Experiment #7: B-Glucan
B-Glucan is a polysaccharide produced by some plants, bacteria and yeasts. It is composed of chains of glucose with varying connections depending on the source. Because of these differences, not all beta-glucans have the same effect on the skin. Even with the same source, many factors (charge, MW, isolation method, length of side chains, solubility, degree of branching etc.) affect the skin. Its primary benefits are as follow:
- Wound healing: It encourages the migration of Macrophages to the site of injury and triggers many growth factors that are important for re-epithelialization and collagen deposition.
- Anti-Irritant: It lessens Interleukin 8 and 1a and reduces the IgE antibody.
- Barrier repair: It rebalances the Th1 /Th2 immune response to lessen the exaggerated activation of Mast cells and IgE antibodies.
- Moisturization: It is purported to increase skin hydration and reduce TEWL.We're focusing on the Moisturization part for this study. Interestingly, there aren't a lot of studies done on its hydration effects. Some beauty sites swear by its hydration effects + TEWL reduction ability, but there's really not a lot written on it.
Purpose:
This experiment aims to assess the hydration effect of Betaine in combination with other humectants.
Procedure
- n=8
- measurement with Corneometer CM825
- au values minus baseline = change in hydration
- t=30 minutes after application
Solutions Tested
Results
The results here confirmed the results we got in our previous humectant series. Weirdly enough, it also dehydrated the skin like HA. In this study, there is no significant difference between the samples. Sample 2 with 1% beta-glucan had a lower hydration level than without it in Sample 1. 
In terms of skin feel, Sample 2 had a higher slipperiness and spreadability than the rest of the samples. However, there is considerable drag from 1%, which increases as beta-glucan increases to 5%.
References
- Costa-Balogh, F., Wennerström, H., Wadsö, L., & Sparr, E. (2006). How Small Polar Molecules Protect Membrane Systems against Osmotic Stress: The Urea−Water−Phospholipid System. The Journal Of Physical Chemistry B, 110(47), 23845-23852. doi: 10.1021/jp0632440
- Nowacka, A., Douezan, S., Wadsö, L., Topgaard, D., & Sparr, E. (2012). Small polar molecules like glycerol and urea can preserve the fluidity of lipid bilayers under dry conditions. Soft Matter, 8(5), 1482-1491. doi: 10.1039/c1sm06273e
- Mojumdar, E., Pham, Q., Topgaard, D., & Sparr, E. (2017). Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum. Scientific Reports, 7(1). doi: 10.1038/s41598-017-15921-5
- Fluhr, J., Darlenski, R., & Surber, C. (2008). Glycerol and the skin: holistic approach to its origin and functions. British Journal Of Dermatology, 159(1), 23-34. doi: 10.1111/j.1365-2133.2008.08643.x
- Hara, M., & Verkman, A. (2003). Glycerol replacement corrects defective skin hydration, elasticity, and barrier function in aquaporin-3-deficient mice. Proceedings Of The National Academy Of Sciences, 100(12), 7360-7365. doi: 10.1073/pnas.1230416100
- National Industrial Chemicals Notification and Assessment Scheme (2019). Acetamide, N-[2-(2-hydroxyethoxy)ethyl]- (INCI Name: Acetamidoethoxyethanol) Public Report, File No: STD/1605.
- Korponyai, C., Kovács, R., Erös, G., Dikstein, S., & Kemény, L. (2011). Antiirritant Properties of Polyols and Amino Acids. Dermatitis, 22(3), 141-146. doi: 10.2310/6620.2011.10082
- Páyer, E., Szabó-Papp, J., Ambrus, L., Szöllősi, A., Andrási, M., & Dikstein, S. et al. (2018). Beyond the physico-chemical barrier: Glycerol and xylitol markedly yet differentially alter gene expression profiles and modify signalling pathways in human epidermal keratinocytes. Experimental Dermatology, 27(3), 280-284. doi: 10.1111/exd.13493
- Korponyai, C., Szél, E., Behány, Z., Varga, E., Mohos, G., & Dura, Á. et al. (2017). Effects of Locally Applied Glycerol and Xylitol on the Hydration, Barrier Function and Morphological Parameters of the Skin. Acta Dermato Venereologica, 97(2), 182-187. doi: 10.2340/00015555-2493
- Draelos, Z. (2019). Cosmeceuticals. Dermatologic Clinics, 37(1), 107-115. doi: 10.1016/j.det.2018.07.001