The detergent is a chemical substance that is used for cleaning and hygiene of our skin. To be a good product, the detergent must remove excess sebum and impurities without drying and depleting the epidermal stratum corneum (note the stratum corneum is the part of the skin in direct contact with the external environment).
In most cases, the chemical structure of the detergent makes it possible to bind the dirt through the lipophilic part and to remove it instead thanks to the hydrophilic fraction that binds to the washing water. This process is called “tensioactivation”.
The detergency and the foaming are all based on this dual nature oil/water of the surfactant.
In the cosmetic sector, there is a wide range of substances that due to their characteristics can have a more or less mild action. The formulator usually combines softening substances or additives to the surfactants to allow a more physiological washing.
We can have two different types of cleansing:
Cleansing by micellization: this is the most frequent cause. The surfactant forms micelles that trap dirt inside them and are then rinsed with water.
Cleansing by affinity: it is based on the affinity mechanism by which detergent (in this case, not a surfactant) and dirt (understood as a mix of sebaceous oils present on the skin) have the same chemical characteristics and are combined together to form a single solution which then it is removed with absorbent agents.
This system avoids the risk of deoxidizing the skin and scalp which could cause a rebound effect on the sebaceous glands. This “affinity” cleansing is indicated for all those people who are allergic to traditional foaming detergents.
Let’s take a closer look at the cosmetic products that contain detergents:
It is the most traditional of detergents. It can have two origins: natural (derived from fatty acids through the saponification process) or synthetic (ie using synthetic surfactants). The origin of the name seems to derive from the Italian city of Savona, where it was manufactured, later superseded by the French predominance of the city of Marseille.
SYNDETS (SYNTHETIC SOAPS)
The disadvantage of soaps is the high alkalinity that they can release on the skin due to the presence of a non-salified free alkaline base, for which in the 1970s syndets, also known as synthetic soaps or soaps, not soaps, were born. However, the starting part is the fat/oil that is chemically processed. They have a good foaming power which is not found in soaps and is not alkaline.
The shampoo has the hair and scalp as its preferred location (but it can also be used for the body.). To counteract the dryness and above all to obtain a good level of combing, the shampoo is added with detangling agents or it is followed by the application of a balm.
BUBBLE BATH / SHOWER GEL
As we said not much different from a shampoo. Usually, the shower gel has a greater active washing since it must be diluted in large quantities of water, while the shower gel maintains a lower percentage of surfactants considering that it is applied directly to the skin. The shower gel often contains conditioning / emollient substances for a silky effect after a shower.
It has a special formulation for both pH and fragrance. Going into contact with the mucous membranes is subject to a more restrictive safety assessment than the other types of detergents seen so far. It has an antibacterial and soothing effect which is guaranteed by the acid pH and the presence of plant extracts (such as marigold, chamomile, mallow).
It usually appears as a milky lotion which is nothing more than a fluid oil-in-water emulsion. It is formulated using a balanced supply of surfactants and emollient and rebalancing agents to guarantee the physiological pH and the maintenance of the hydrolipidic film.
These cosmetic products act by affinity and not by micellization. In fact, excess sebum or make-up impurities are solubilized by an oily mixture which is removed by a physical removal mechanism with a cotton pad.