Most personal care products are emulsions which can be defined as stabilised fluid systems of liquids that do not normally like to mix, like oil and water. The peacekeeper in such systems is called an emulsifier. Emulsifiers combine a water-loving head holding to the water phase and a fat-loving tail that clings to the oil phase.
Oil-in-water (o/w) emulsifiers keep oil drops packed in water, while water-in-oil (w/o) emulsifiers rather retain water drops in oils. Classic emulsifiers are typically synthetic petroleum and hydrocarbon derivatives such as PEG compounds, alkoxylated amides, silicone derivatives, and ethoxylated fatty alcohol. They present the advantages of being performant, rather inexpensive, easy to work with and readily available. On the downside, some can cause skin irritation and allergies. This happens because they keep their emulsifying properties while penetrating the skin. Lipids can thus be washed away from the stratum corneum altering the multilamellar structure of the latter and compromising the barrier function of the skin.
The current trend in skin care is for natural, gentle and safe products, obtained in a sustainable manner. With the help of the Internet, end users (especially Millennials) are now better informed and take the time to read product labels in order to identify potential harmful ingredients. Formulators should keep this in mind when choosing an emulsifier. What is the point of formulating with the most natural actives, if the ingredient list ends with chemical names of bad reputation? But, are there alternatives to classic petrochemical emulsifiers and how do their performances compare?
Phospholipid-based emulsifiers offer great natural alternatives. Phospholipids generally consist of a hydrophilic phosphate head and two hydrophobic fatty acid tails joined together by a glycerol molecule. In an aqueous environment, phospholipids spontaneously arrange in bilayers in which hydrophobic tails line up against each other, while hydrophilic heads face water molecules on both sides. All living cells are surrounded by such a phospholipid bi-layer that protects them and regulates what goes in and out.
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