Podcast: Episode 12, the moisturizer

Audio episode, the moisturizer


The moisturizer is an emulsion (see episode 2). That is to say that it contains an aqueous phase and a fatty phase to moisturize and soften the skin.

The aqueous phase

  • water / juice
  • glycols
    • ex : glycerin, butylene glycol, pentylene glycol, diglycerin, propanediol
  • gelling agents / thickeners
    • natural ex: xanthan gum, sclerotium gum, pullulan, caesalpinia spinosa gum
    • ex conventionels : carbomer, acrylate ou polyacrylate crosspolymer (caprylate / C10-30 alkyl acrylate crosspolymer, polyacrylate-1 crosspolymer)
  • active ingredients or plant extracts
    • ex : hyaluronic acid, ascorbic acid
  • pH adjuster
    • ex : citric acid, sodium hydroxide
  • conservative
    • ex : phenoxyethanol, sodium benzoate, potassium sorbate
  • chelating agent
    • ex naturel : phytic acid
    • former conventional: EDTA

The fatty phase

  • emulsifying
    • natural ex: les alcools gras (-yl + alcohol : cetearyl alcohol, stearyl alcohol, …), les glyceryls + -ate (glyceryl stearate, glyceryl oleate, …)
    • ex conventionels : les PEG + -ate (PEG-8 laurate, PEG-8 stearate,…), les -eth + nombre (les steareth, beheneth, pareth, ceteareth, ceteth, laureth,… : steareth-4,…), les polysorbates + nombre.
  • oils, butters, waxes
    • natural ex: jojoba oil (simmondsia chinensis (jojoba) seed oil), beurre de karité (butyrospermum parkii (shea) butter), carnauba wax (copernica cerifera (carnauba) wax), limanthes oil (limenthes alba (meadowfoam) seed oil)
    • former conventional: ozokerite, paraffin, liquid paraffin
  • actives / antioxidants
    • ex : tocopherol (vitamin E)
  • scent

Episode Notes


Hello, you are listening to episode 12 of The Sous de la Cosmétique, the Podcast which reveals and explains to you with clarity and sincerity the world of cosmetics. I am Julie Magand Castel, chemical biologist and cosmetologist specialized in natural cosmetics and today we are going to talk about moisturizing creams. It is a facial, body, hand, foot care, and we will see its usefulness, and its ingredients by going a little bit through its chemistry.

So what is a moisturizer, what is it for? It is a cosmetic product that serves to moisturize and soften the skin of different parts of the body - face, hands, feet, legs - regardless of the formulation remains almost the same.

What are the ingredients that then make it possible to hydrate and soften the skin? Moisturizers contain moisturizing ingredients like glycols. The best known glycol is glycerin, which can be of vegetable or petrochemical origin. Glycerin and moisturizing ingredients in general are also called humectants. They moisten the skin, ie they bring enough water to the skin for it to function normally.

Generally these humectant ingredients are water soluble, they mix easily in water. So the glycols are for the hydration part, but the cream also contains ingredients that soften the skin, which nourish it. In this category, mention may be made of vegetable oils such as jojoba oil, vegetable butters such as shea butter or vegetable waxes such as carnauba wax, for example. All these ingredients are not soluble in water, they do not mix with water.

Conversely, they are soluble in oil, they are said to have started from the fatty phase. So obviously to mix them with oil, you have to heat the butters and waxes to melt them and be able to mix them with jojoba oil for example. So we just said that glycols hydrate and are soluble in water whereas oils and butters nourish and do not mix in water.

So I'm sure if you haven't listened to Episode 2 of the Podcast called Mayonnaise and Salad Dressing, you're wondering how ingredients that don't mix end up together in one product. So, I strongly invite you to listen or re-listen to episode 2 to fully understand everything we are going to talk about next. In this episode 2, we were talking about emulsion. And the emulsion is the secret to having a product that contains glycols and oils while being stable, ie that does not change appearance over time.

The main ingredient of an emulsion is the emulsifier. The emulsifier is an ingredient that will bind both water-soluble ingredients and oil-soluble ingredients. And so, thanks to the emulsifier, glycols and oils, butters, waxes and others cohabit in the same product. On the other hand, by creating an emulsion, the product becomes white.

Now that we have understood that a moisturizer is an emulsion, we can talk about its ingredients. It has been said that the star ingredient in terms of stability isemulsifying. It is customary to classify emulsifiers according to their electronic charges. We will talk about anionic, cationic or non-ionic surfactants in a future episode. To give some examples of natural surfactants, there are fatty alcohols: cetearyl alcohol, stearyl alcohol, then glyceryl + ate such as glyceryl stearate, glyceryl oleate. Conventional surfactants there are PEGs that end in -ate so for example PEG-8 laurate, PEG-8 stearate, then there are steareth like steareth-4, and others ending in eth like beheneth , pareth, ceteareth, ceteth, laureth, etc, followed by a number. Then there are polysorbates also followed by a number.

As we have seen, the emulsion serves to stabilize the aqueous phase and the fatty phase. For oil in emulsionswater, which dominate the moisturizing cream market, the aqueous phase dominates. One of the first ingredients on the INCI list is water, which is used as a solvent. Then in the aqueous phase may contain glycols comme la glycerin, le butylene glycol, le pentylene glycol, la diglycerin, le propanediol. They moisturize the skin and help preserve the cream, to fight against microbial contamination.

The gelling agents and thickeners are also placed in the aqueous phase to thicken the product. To be completely exact, we can distinguish between thickeners and gelling agents. The main purpose of a thickener is to thicken the product whereas the gelling agent creates a three-dimensional network in the product which stabilizes the structure of the latter. So it helps with stability. Often in creating this three-dimensional network, the gelling agent also thickens the product. This is why sometimes, we do not always distinguish between these 2 terms. Here are some examples of natural thickeners and/or gelling agents: xanthan gum, so on the INCI list it's xanthan gum, sclerotium gum, pullulan, tara gum on the INCI is caesalpinia spinosa gum. And in the conventional ingredients, the most used are the carbomer which you can directly find in the INCI list as carbomer. There are also acrylate or polyacrylate crosspolymer that you can find on the INCI list as carylate / C10-30 alkyl acrylate crosspolymer or polyacrylate-1 crosspolymer for example. Some plant active ingredients or extract are also put in the aqueous phase like hyaluronic acid and ascorbic acid therefore vitamin C.

Then the pH adjusters are also put in water like citric acid if you want to lower the pH or soda so sodium hydroxide so in the INCI that you find as sodium hydroxide.

And then the conservatives are put in the aqueous phase like phenoxyethanol, sodium benzoate or potassium sorbate. Certain chelating agent also enter the aqueous phase. The chelating agent prevents the metallic ions from reacting with the other raw materials of the cream and altering them. They therefore help the stability of the cream. Ions are unstable and react very easily with other molecules. They can come from water depending on its degree of purification, manufacturing equipment, raw materials.

In natural cosmetics, phytic acid is widely used and EDTA remains the darling of conventional cosmetics. They are not systematically used in emulsions but are very useful if other raw materials are sensitive to metal ions. Here we have done a good tour of the aqueous phase of a moisturizer. To recapitulate, the aqueous phase contains water, glycols, one or more gelling agents, preservatives, pH adjusters, potentially a chelating agent, aqueous active agents or extracts.

And then sure we can talk about the fatty phase. The fatty phase will give body to an oil-in-water emulsion because it is the phase which is suspended in the external phase in the form of small droplets. In general, the greater the interior, the more droplets there are in suspension, the thicker the emulsion. It can consist ofvegetable or mineral oil. The vegetable oils often used are jojoba or medowfoam oil so I think in French we say limnanthes but honestly we call it more often by its English name because it is the one we see on the INCI. There is also caprylic/capric triglyceride. Certain alkane or ester are natural, squalane, Coco-Caprylate/Caprate.

The mineral oils are those derived from petrochemicals such as paraffinum liquidum. The vegetable butters and waxes such as shea butter, mango butter, carnauba wax. The fatty alcohols mentioned in the emulsifying parts are also part of the fatty phase such as cetearyl alcohol, stearyl alcohol. They are generally sold in the form of small beads or wax flakes. This makes it easier for the formulator to weigh and melt. And then there are the mineral waxes or derived from petrochemicals such as Ozokerite or paraffin. The moisturizer also contains other ingredients which are soluble in oil such as vitamins or active ingredients and fragrance.

However, these raw materials are more sensitive to heat and are generally incorporated after the emulsion has been formed and cooled so as not to alter them. To take an example of a fat-soluble active ingredient, vitamin E, also called tocopherol, goes into oil. It is a very good antioxidant so can help stabilize the cream by preventing oxidation reactions.

Oils are particularly affected by oxidation which may cause them to turn yellow and develop a rancid smell. Tocopherol is often present in emulsions but also in oils. Tocopherol is the most used antioxidant in natural cosmetics and BHT is a very powerful antioxidant used in conventional cosmetics. So to summarize, the oily phase of a moisturizer is composed of oil, butter, wax, active ingredients / antioxidant, perfume and generally we can count the emulsifier in it as well

So to sum up, a moisturizer has a double action on the skin, it hydrates it and softens it. It is an emulsion and is therefore composed of a fatty phase and an aqueous phase. The aqueous phase contains water, glycols, one or more gelling agents, preservatives, pH adjusters, potentially a chelating agent, aqueous active agents or extracts. And the fatty phase is composed of oil, butter, wax, active ingredients/antioxidant, perfume and emulsifier.

I hope you enjoyed this episode and helped you understand your moisturizer ingredients. We talked about a lot of ingredients and I can imagine that just listening to this episode is not enough. So don't hesitate to go see the notes of this episode with all the ingredient names on mastelcosmetics.com in the underside of cosmetics section. Mastel is written MASTEL and is the contraction of my two surnames Magand Castel. Do not hesitate to react in the comments, to ask your questions or to indicate what you would like to hear next.

You can subscribe to the Podcast The sous de la beauté today on various Podcast platforms including Spotify, Apple Podcast or Google Podcast and follow its news on Instagram and Twitter with the username mastelcosmetics. Also and of course feel free to share this podcast with your friends if you think they might enjoy it - thank you. I wish you a great week and see you next Saturday for an episode on the patch test. The patch test is a test method that we do during the development of our product to ensure its tolerance.

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A chemist in the cosmetics industry for more than 5 years and a graduate of the Natural Raw Materials in Cosmetics Master's degree from ISIPCA, Julie is an expert in the development of natural cosmetic products.