Stratum Corneum is composed of 20-30% corneocytes which is where you will find NMFs
The outermost layer of the skin is known as the stratum corneum (SC). This is your defense layer from outside allergens, but is also home to the Natural Moisturizing Factors (NMFs). The stratum corneum is composed of corneocytes, which is where you will find the NMFs, and corneocytes make up 20-30% of your stratum corneum.
Some common NMFs are; amino acids, hyaluronic acid, sodium PCA, lactic acid, ceramides, fatty acids, phospholipids, glycerin, saccharides, pyrrolidone, carboxylic acid, triglycerides, & Urea, which is what I want to talk about today.
Side note; FSS sells this amino acid blend which contains a blend of these NMFs and specifically a bunch of amino acids.
Urea
White to off-white crystal/powder
Water soluble. (Meaning it will dissolve in water.)
1 gram or urea will dissolve in; 1 ml of water, 10 ml of 95% alcohol, or 2 ml of glycerol. (I will be using water to dissolve it.)
Has moisturizing and hydrating benefits
Replenishes natural skin urea lost to cleansing
Exfoliates the skin
Can act as an anti-inflammatory on damaged skin
Add to water phase of formulations
Recommended usage rate; 2-5% or up to 40%
Can work as a keratolytic agent (reduce dead skin build up) when used at high amounts. (10-20%)
Can be used to treat nail fungus at 20% or higher
Has deodorizing effects, which make is great for foot products and deodorants.
Most stable in a pH between 4-8
pH of products using urea will increase in hot climates causing instability. (Might need paired with a low pH ingredient like an AHA or BHA to keep pH stable.)
Fun Fact, Urea can be found in the urine of mammals, but we make it synthetically for our cosmetics. So don’t worry, we aren’t using urine here.
Important info about formulating with Urea;
(According to myskinrecipes.com) Urea has long-term disintegration characteristics. Which means it will lose it’s strength or destabilize overtime. Being in the heat causes this more quickly. (35°C / 95°F) Urea can cause the pH of your formula to rise (become more alkaline). Leaving your product in a hot place for only 3 months could cause the pH to rise to 11. So having some kind of stabilizer with Urea is very important.
You can use Gluconolactone as a stabilizer. It is recommended to use gluconolacctone in an amount of 15% of Urea. So if you used Urea at 10%, then you would use Glyconolactone at 1.5%. This will help keep the pH stable.
Urea will also make your formula smell. So you can use Triacetin to help reduce the odor. You want to use 1(triacetin):10(Urea) (According to myskinrecipes.com)
Glyconolactone is an PHA, more gentle than lactic and glycolic acid. So if you don’t have Glyconolactone, you can use lactic acid. And this is a common ingredient used to help stabilize Urea. It would also be a good idea to use some kind of chelating agent like Sodium Phytate or Disodium EDTA
Experiments
I’ve never used Urea before. So I want to do a couple experiments.
As stated above it mentions that you need Glyconolactone as a pH stabilizer. Well I don’t have this. So instead, the next best thing is lactic acid, since this is very gentle and when used at a lower percent, is even more gentle. So I think this would be a good option.
I did check out some example recipes using Urea on makingcosmetics.com and aromantic.co.uk which didn’t include a low pH AHA like lactic acid or Glyconolactone. So I am thinking, if I use Urea at a low enough percent, I might not need the assistance of this pH adjuster. The makingcosmetics.com recipe does include a chelating agent, while the aromantic.co.uk recipe does not. Now these recipes from suppliers aren’t always the best references, as they are sometimes not the most stable, but they are still good inspiration and I use them whenever I am trying to learn how to formulate with a 'new to me’ ingredient.
So I am going to try to make a very basic (minimal ingredients) body lotion with 5% Urea. I’m thinking this might be a low enough percentage that it won’t need the assistance of an acidic ingredient like lactic acid or Glyconolactone.
So I am going to do a 5% Urea lotion experiment with a chelating agent and a 5% Urea lotion experiment without a chelating agent to compare how they turn out. The one with the chelating agent will also include lactic acid to help lower the pH, since my chelating agent raises the pH. I will be using Sodium Phytate as my chelating agent. (If you are using Disodium EDTA you can try it without the AHA, but I’m not sure how it will work out for you)
I am going to do two other experiments the same way, except I will be using 10% Urea.
Since the pH might drift I want to use an emulsifier that is stable in a wide range of pH. So you could use Olivem 1000, Emulsifying Wax NF/Polawax, Montanov 68 MB, or any other all in one emulsifier that is stable in a low pH. (Not all emulsifiers are)
Another thing I want to mention is that Urea is a humectant and moisturizer, it is commonly used in products to help repair dry flakey skin. At lower percentages it just moisturizes and hydrates, then at higher percentages it can actually act as an exfoliant, which paired with its hydrating & moisturizing benefits, makes it perfect to treat problem areas like elbows knees and feet. So don’t be scared to make this a thicker moisturizer. You can use heavier oils, butters, or anything else you like in a moisturizer for those troubled areas.
One more thing, when doing experiments, its always best to start with minimal ingredients because your formula might not work out, so you don’t want to waste all your expensive ingredients. Plus, if the formula fails, it’s harder to figure out what might be causing the issue if you have all these ingredients in there. So that is why I like to stick with a minimal formula when experimenting.
The main thing I am trying to figure out with this experiment is;
How much pH buffer (Lactic Acid) will I need to get the pH between 4.5 - 5.5?
How well does the Urea dissolve?
Will the Urea recrystallize?
Long term things I am trying to figure out with this experiment;
Will the pH of the product increase overtime?
Will the addition of sodium phytate and lactic acid help the pH stability?
Will Urea cause any destabilizing of emulsion?
Does it Smell Odd?
Here are my experiments;
Urea Lotion Test 1 - natural pH 5.7
Phase A
5% Urea
5% Glycerin
61.5% Distilled water
Phase B
5% Shea Butter
10% Apricot Kernel Oil
5% Macadamia Nut Oil
6% Emulsifying Wax NF
2% Cetyl Alcohol
Phase C
0.5% Liquid Germall Plus
Urea Lotion Test 2 - natural pH 5.7
Phase A
10% Urea
5% Glycerin
56.5% Distilled water
Phase B
5% Shea Butter
10% Apricot Kernel Oil
5% Macadamia Nut Oil
6% Emulsifying Wax NF
2% Cetyl Alcohol
Phase C
0.5% Liquid Germall Plus
Urea Lotion Test 3 - natural pH 9.46
Phase A
5% Urea
5% Glycerin
60.45% Distilled water
0.05% Sodium Phytate
Phase B
5% Shea Butter
10% Apricot Kernel Oil
5% Macadamia Nut Oil
6% Emulsifying Wax NF
2% Cetyl Alcohol
Phase C
0.5% Liquid Germall Plus
1% Lactic Acid (not sure if I will need this much, but I left a whole 1% open in this formula incase I do)
- natural pH 9.46
- used 6 drops of lactic acid or 0.24 grams
- final pH 4.46
Urea Lotion Test 4 - natural pH 9.25
Phase A
10% Urea
5% Glycerin
55.45% Distilled water
0.05% Sodium Phytate
Phase B
5% Shea Butter
10% Apricot Kernel Oil
5% Macadamia Nut Oil
6% Emulsifying Wax NF
2% Cetyl Alcohol
Phase C
0.5% Liquid Germall Plus
1% Lactic Acid (not sure if I will need this much, but I left a whole 1% open in this formula incase I do)
- natural pH 9.25
- used 6 drops of lactic acid or 0.24 grams
- final pH 5.05
Directions to make lotions;
Combine phase A in a heat safe beaker.
Combine phase B in a heat safe beaker.
Tare scale and weight phase A. Take not of the weight. We will be heating it up and some of the water will evaporate and we will need to replace that water after heating.
Create a water bath by filling a pan with about an inch of water and place over medium heat.
Place both phase A and B in the water bath and heat until phase B is melted and phase A is around the same temperature.
Once phase A is around the same temperature as phase B and phase B is melted, you can remove from heat.
Before pouring phase A into phase B make sure you replace any water in phase A that evaporated.
Then after you poured phase A into phase B, you can mix with an immersion blender.
Let phase A/B cool.
Once phase A/B is around 104°F / 40°C you can add in the phase C ingredients.
pH adjusting - For Experiment 3 and 4 you want to add in a couple drops of lactic acid or other solution to lower the pH until you lower the pH to around 4.5 - 5.5 Doesn't need to be exact. Watch my video all about pH here you can also watch the video version for a little more info on how I made these.
How I am storing the Experiments
I divided each experiment into two separate jars. I labeled and dated each jar. I placed 1 jar from each experiment in my lab where it stays around 70°F / 21°C & I placed 1 jar from each experiment in my incubator at 95°F / 35°C. I am going to leave those jars there for 3 months to see if the pH changes for any of them and to see if they end up with some kind of strange smell. I will update you all in 3 months.
Sources;
I am a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for me to earn fees by linking to Amazon.com and affiliated sites.
I am an affiliate with Makesy.com and some links may be affiliate links.
Commenti