Mechanical Exfoliation: What is a facial scrub made of?

Skin cells take 28 days on average to renew themselves. Biologically speaking, epidermal renewal is the process of generating keratinocytes in the basal layer of the epidermis, coupled with the loss of corneocytes (dead cells) on the skin's surface. Throughout this cycle, dead cells accumulate, clog the pores, and dull the complexion. That's why a weekly exfoliation is essential to prepare the epidermis for care, deeply unclog the pores, and stimulate blood circulation. In summary, exfoliation helps to improve skin texture and its overall appearance.

There are two methods: themechanical exfoliation or scrubbing and thechemical exfoliation or peeling. The difference between the two lies in the mode of action of the detachment of dead cells on the skin's surface:

• Generally, a chemical peel involves substances known as AHA (alpha-hydroxy acids), BHA (beta-hydroxy acids) and PHA (poly-hydroxy acids. These molecules eliminate keratinocytes by breaking the ionic bonds, thus destabilising the horny layer and causing its gradual detachment.

• Mechanical exfoliation or scrubbing lifts dead cells from the epidermis through friction. There is no "chemical" action on the surface of the epidermis. Depending on the size of the solid particles present in the product for abrasion, mechanical scrubbing can be more or less aggressive for the skin. Micro-grains such as powders derived from fruit kernels are often favoured for exfoliating the face and chest. Larger grains, on the other hand, allow for the exfoliation of parts of the body where the skin is thicker and less sensitive, such as the feet or legs.

Scrubs are typically formulas whose base is an emulsion or a gel. The abrasive compounds added at the end of the formulation process can be:

• Of origin vegetable such as powders derived from the kernels of certain fruits;

• Of origin mineral such as microcrystals of alumina;

• Of origin synthetic such as polyethylene microbeads. Even though these compounds have been banned in cosmetic products in France since 2018 due to their accumulation in the oceans, they still make up some formulas present on the global market.

The selection of ingredients depends on the desired outcome and the type of skin to be exfoliated. Fine grains are particularly gentle for facial skin, which is quite delicate. Larger or more angular grains, on the other hand, are recommended for body exfoliation.

Typology has developed two exfoliating facial treatments using micro-exfoliating grains derived from the grinding of apricot kernels :

• The radiant facial scrub to unclog pores and promote cellular renewal;

• The regenerating facial scrub to diminish the appearance of early signs of ageing.

These two scrubs exhibit a unique texture: they are gels that transform into exfoliating oil under the effect of massage, then emulsify into milk upon contact with water, thus facilitating their rinsing. This type of texture has a name in formulation: a "D-phase" gel. This is composed of a majority oil phase (here rich in vegetable oils) and a minority aqueous phase. The advantages of this type of gel are numerous. Formulated cold, it allows for the maximum preservation of the qualities of the active ingredients and vegetable oils. Moreover, as water is present in a small quantity, the D-Phase gel does not necessarily require preservatives to prevent the growth of pathogenic microorganisms.

• KANDASAMY R. & al. Skin care with herbal exfoliants. Functional plant science and biotechnology (2011).

• KAZUHISA M. New method of measurement of epidermal turnover in humans. Cosmetics (2017).