About Cosmetic Formulation and the Skin/Part 2

Learn how to formulate more consciously and improve your formulation efficacy.

In Part 1, we discussed what happens with the formulation when applied onto the skin, and in Part 2 we will look into formulation types and their impact on ingredient penetration and skin permeability.

Let's start with the simplest product types, solutions.

One phase products

Liquids such as water and thin-bodied oils are able to penetrate the skin. Actives dissolved in those liquids are “dragged” into the skin with the solvents. A large amount of dissolved active ingredient molecules in the base results in good penetration, and the affinity of the active to the skin should be as high as possible. Good to be aware that using ingredients with a similar penetration profile will make them compete, and if we want to increase one particular active penetration rate, it’s better to use it alone and at higher concentrations. We can also control the rate of penetration by choosing the right medium of our solution. A perfect example of that is retinol. If it’s too compatible in the medium (polar emollients), there is no driving force for it to leave the product film and penetrate. When formulated in non-polar emollients (such as mineral oil) the penetration rate is higher (but be aware that the irritation potential increases at the same time!).

Now, moving onto more complex formulations.

W/O Emulsions

the application of w/o emulsion can cause an occlusive effect, under which the hydration of the horny layer takes place, resulting in increased penetration.

Lamellar O/W Emulsions

Multilamellar liquid crystal-based emulsions penetrate much better due to high compatibility with the skin cement structure. Some emulsifiers and waxes can easily assist in the formation of liquid crystals, such as lecithin, fatty acids & alcohols, sodium stearoyl glutamate, cetearyl glucose, glyceryl behenate, and more. The very high affinity of lamellar systems to the skin barrier also results in improved sensorial aspects and reduced TEWL (less water escaping the skin).

Micro/Nano Emulsions

Micellar solutions and high sheer processing reduces the particle size and increases skin penetration. Microemulsions can facilitate the penetration of polar and moderately lipophilic ingredients.

SPF Products

Sun protection products loaded with high level of solid particles powders such as TiO2, ZnO may increase ingredients penetration. The reason for that is the formation of a liquid film called “meniscus” between the particles and the skin when the liquid of the formulation dries out. The liquid film contains an increased concentration of dissolved active, ensures prolonged residence time on the skin, and as a result, penetration is locally increased.

Exfoliating Products

I am sure you know that exfoliating the skin before applying an active can increase penetration and product efficacy. That includes chemical exfoliation (AHA’s, BHA’s, enzymes), abrasives, or electric/ mechanical brushes.

In the last Part 3, we will go through specific ingredient groups.

Let's create beauty together.