How does skin pH affect the choice of cleansers?

Liya Savvina , dermatologist, cosmetologist, trainer at Aesthetics Holl Medical Center

Skin care begins with cleansing, and the priority task of cosmetic products that perform this function is to remove external contaminants - remnants of decorative cosmetics, toxins from the environment, and excretion products.

The second mandatory functional component of cleansers is maintaining or, if necessary, restoring the function of the skin barrier and its integrity.

The barrier function of the skin and the normal condition of its surface are ensured by the epidermis. In the reliability of the skin barrier, particular importance is attached to the stratum corneum, which is a specific component of the physical barrier. The stratum corneum serves as a “barrier” to chemicals and microorganisms in contact with the skin, withstands mechanical stress, regulates the processes of moisture evaporation (TEW - transepidermal water loss), that is, it actively participates in maintaining a person’s internal homeostasis.

Violation of the barrier function due to an irrational choice of skin care products or excessively thorough cleansing (using water and detergents) can be caused by a number of factors: destruction of the acid mantle of the skin (Marchionini mantle), changes in its pH, a decrease in the amount of sebum lipids or disorganization the state of the lipid bilayers of the epidermis (ceramides, free fatty acids, cholesterol), as well as a disorder of cohesion (adhesion) of the corneocytes of the upper layers of the stratum corneum.

The importance of surfactants in cleansers

The main cause of skin pathology may well be the use of inexpensive mass-market cleansing products containing cationic surfactants (surfactants: ammonium lauryl sulfate, dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide, etc.) or anionic surfactants (sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl sulfate, etc.) etc.).

Depending on the charge of the ions, the toxic properties of surfactants also differ:

• Cationic surfactants form strong bonds with negatively charged functional groups of proteins, lipids, phospholipids and other compounds of the lipid bilayer.
• Anionic surfactants interact with skin structures less strongly than cationic ones.

And both of these groups have an irritating effect , which is caused by the denaturation of proteins and enzymes. Violation of protective systems leads to an increase in TEWL, a decrease in the amount of moisture in the skin, clinically this condition is manifested by a feeling of dryness, itching of the skin, peeling, tightness, irritation and redness. In addition, cleansers with a high pH cause compensatory hypersecretion of sebum.

Today, the tendency to produce low-quality cosmetics using outdated recipes, unfortunately, still persists. These cosmetics are sold at a low price, which is of great importance to the consumer.

Regardless of skin type and condition, modern cleansers should include dermatologically mild and multifunctional surfactants with a wide spectrum of action. Taking into account the conditions stated above, such surfactants include biosurfactants (biosurfactants, Greek bio(s) - “life” and English surfactant - “surfactant”). The main properties of biosurfactants are their biocompatibility with the skin and generally very low toxicity. They are a product of bacterial metabolism or components of their cell membranes. An example of a modern anionic lipopeptide biosurfactant is the sodium salt of surfactant (Surfactinsodium), and an example of a high-tech glycolipid is rhamnolipid.

To select the optimal cleanser, the cosmetologist focuses on skin characteristics such as texture and secretion . Taking into account the skin type and its condition, in addition to removing external impurities, detergents and cleansers for it should include biologically active components to restore the natural barrier systems of the skin or prevent their deterioration, while simultaneously improving the health of the skin in general. The choice of cosmetic products should lean towards emollients, moisturizing components and transdermal carriers related to both the aqueous and lipid phases of the epidermis. To achieve the best results, active ingredients must directly bind to damaged or involved cells and systems.

An important condition for maintaining the normal appearance of the skin and its health is maintaining optimal water balance in the tissues and restoring the level of moisture in the stratum corneum. The aqueous phase is integral to the lipid phase - it is a single system; it is impossible to maintain or correct one without the other.

Wetting agents

The category of cosmetic moisturizers includes any substance that helps increase water retention in the stratum corneum. Humidifiers differ in their chemical nature and mechanism of action.

• Hygroscopic humectants absorb moisture from the air and surrounding tissues and retain it inside the stratum corneum (urea, amino acids, lactic acid, sodium lactate, butylene glycol).
• Moisturizers with film-forming properties do not penetrate the stratum corneum (hydrolyzed whole grain wheat protein, soluble hydrolyzed collagen/elastin, beta-glucan, colloidal oatmeal, sodium hyaluronate/ hyaluronic acid ).
• Hydrophobic moisturizers with occlusive properties create a film on the surface of the skin that physically prevents the evaporation of water (tocopherol linoleate, ceramides, sphingolipids, lipoamino acids of plant origin, phospholipids, glycopolypeptides), and the list of occlusive components largely overlaps with emollients.

As mentioned, the price of skin care products will generally be a reflection of the quality of the surfactant - the same is true for the quality of the moisturizer. Higher quality moisturizers will imitate the work of the water-retaining and water-regulating structures of the stratum corneum and will cost more. Wheat proteins help reduce the irritating effect of surfactants and also have foaming and emulsifying effects. The properties of wheat and oat derivatives as humectants and emollients, along with their unique amino acid profile, have allowed them to make a major contribution to the cosmetic industry. Many products of marine origin have a beneficial effect on the skin and restore its water balance. Algae are a rich source of amino acids, which are part of the natural moisturizing factor.

Emollients

Cosmetic and personal care products include emollients. Physiological are those emollients that are present naturally on the surface of the skin, softening and protecting it. First of all, these are components of the hydrolipid mantle of the skin, as well as epidermal lipids that form the lipid barrier in the stratum corneum (triglycerides, free fatty acids, essential fatty acids, ceramides and sphingolipids). To gently cleanse dry and sensitive skin, you need to choose a cleansing emulsion or creamy gel wash that combines the properties of a rich cream and detergent. The emulsion can contain up to 90% lipid substances, due to which, along with cleansing, it delivers fats into the deep layers of the skin and creates a lipid film on the surface of the epidermis that prevents moisture loss, washes the skin without soap, without destroying its natural hydrolipid mantle.

Keratolytics

Keratolytic components are often added to skin cleansers. Keratolytic action is effective when corneocyte exfoliation is impaired. The renewal of keratinocytes and their desquamation are responsible for the smoothness and uniformity of skin texture. The accumulation of dead cells appears as uneven skin with a light-reflecting sheen. Weak desquamation of corneocytes is a consequence of insufficient breakdown of corneodesmosomes in the stratum corneum of the skin, caused by a deficiency of unsaturated fatty acids and the lack of free water.

The meaning of the term “keratolytic” translated from Greek means “destruction of the horny substance.” The most popular keratolytic agents include salicylic acid and hydroxy acids (like tartaric, citric, lactic, malic, glycolic, etc.). The most suitable for all skin types, including problem skin (due to their gentle and superficial action), are enzymatic, or enzymatic, keratolytics (papain, bromelain, ficin, actinidin, arbutin, sorbain). When compared with fruit acids, with the same target effect, proteolytic enzymes have a much less damaging and irritating effect. Today, a new approach to the treatment of hyperkeratosis is available, based on the use of peptides. Such peptides can selectively destroy corneodesmosomes. The new cosmetic ingredient is known as Perfection Peptide P3 (arginine-alanine-norleucine).

Features of pH level and skin type when choosing products

There are many different skin conditions that can be caused or aggravated by the use of cleansers with elevated pH. Cleansing the skin with highly alkaline soaps or other similar products can lead to temporary loss of the acid mantle, and regular repetition of these procedures will change the pH of the skin, which will affect the stratum corneum of the epidermis. If you use products for cleansing that contain low-quality surfactants with abundant foaming, it will be very difficult for the skin to restore its pH (skin with impaired barrier function is formed). As a rule, all products for professional use have a balanced pH; special attention should be paid to mass market products.

About 90% of visits to a dermatocosmetologist are patients with oily and mixed skin types. The most common complaints are increased greasiness and the appearance of rashes on the skin of the face, chest and back. Cleansers for oily skin types, first of all, should not provoke compensatory secretion of sebum (have a pH equal to the pH value of healthy skin). Skin care for patients with acne may include a gentle impact on the pathogenesis. For this purpose, cleansing products for oily and problem skin include disinfectant and anti-inflammatory components (salicylic acid, hydroxy acids, retinaldehyde, zinc derivatives, copper, etc.). Cleansers for washing oily skin must also be selected according to their structure. It is better to give preference to water-based gel products.

Conclusion

The importance of basic knowledge in the field of cosmetic chemistry for modern cosmetologists and estheticians is becoming increasingly obvious. The development and introduction of new chemical substances into cosmetics make it possible to optimize skin care. Modern care for any skin type should include two main effects: gentle cleansing and adequate moisturizing.

First published: Cosmetologist No. 1, 2019