FR3090324A1 - Process for treating human keratin materials - Google Patents

Abstract

Process for treating human keratin materials Cosmetic treatment process, comprising the steps of: (a) Applying to an area of human keratin materials to be treated, in particular the skin or the scalp, an acidic composition to reduce the pH thereof ci, (b) subjecting said zone to a plasma treatment, preferably after step a). Figure for the abstract: Fig. 2

Description

Description

Title of the invention: Process for treating human keratin materials

Technical area

The present invention relates to treatments of human keratin materials, and more particularly but not exclusively non-therapeutic treatments for cosmetic purposes, and sets for carrying out such treatments.

Prior art

Systems delivering cold atmospheric plasmas have been used for a few years in the medical field for applications for example of sterilization and treatment of infected wounds. These systems are mainly based on a plasma production technique called DBD (Dielectric Barrier Discharge) and so-called jet plasmas, using a feed gas such as helium or argon.

Application WO 2011/144344 A2 discloses a device for at least partially sterilizing a surface contaminated, in particular with pathogenic germs, using cold atmospheric plasma; various arrangements of plasma production electrodes are described and a large number of applications are mentioned, such as, for example, deodorization.

It is known from the publication Clinical Plasma Medicine 2 (2014) 38-49, that a cold atmospheric plasma generated in the air or an aqueous solution adjacent to the plasma produces reactive species derived from oxygen and l 'nitrogen, called RONS ("reactive oxygen and nitrogen species" in English). These reactive RONS species are produced by the discharge leading to the plasma. The main reactive RONS species generated are hydrogen peroxide H ₂ O ₂ , excited molecular species such as singlet oxygen O _2j radical species such as atomic oxygen O ·, atomic nitrogen N ·, OH · , NO ₂ ·, NO ·, positive ions such as O ₂ ⁺ , N2 ⁺ , N ⁺ , negative ions such as O, O2, ONOO, NO ₂ and NO ₃ . The antimicrobial effect of cold atmospheric plasmas is mainly explained by the generation of these reactive species.

It has been shown that, applied to an aqueous solution, the antibacterial effect of cold plasmas depends on the pH of this aqueous solution.

The article Effects of pH on Bacterial inactivation in Aqueous solutions due to LowTemperature Atmospheric pressure plasma application - 2010 - S. Ikawa, shows that the lower the pH of the solution containing a suspension of bacteria, the more anti-bacterial faction plasma applied to this solution will be rapid. The optimal pH seems to be around 3.7, while for a pH between 4.7 and 6.5 the effect of the plasma is much slower, even nonexistent for a pH of 6.5.

The natural pH of the skin is between 4.5 and 5, as recalled in the article 2006 Lambers - Natural skin surface pH is on average below 5, which is beneficial for its resident flora. This article also shows that the pH of the skin can be directly influenced by a topical solution applied to the skin, and that very often, alkaline cleansers and even tap water tend to increase the pH of the skin.

It has also been shown that acne-prone skin has a higher pH (pH 6) than non-acne skin (pH 5) (2017 - SKIN SURLACE pH IN ACNE VULGARIS insights from an Observational Study and Review of the Literature) .

Statement of the invention

The invention aims to improve the efficiency of plasma treatments of human keratin materials, in particular in order to increase the antibacterial effect of plasmas. Summary of the invention

The invention aims to meet this need and relates, according to a first of its aspects, to a treatment process, in particular cosmetic, comprising the steps consisting in:

A. Apply to an area of human keratin materials to be treated, in particular the skin or the scalp, an acid composition to reduce the pH thereof,

b. subjecting said zone to a cold plasma treatment, preferably after step a).

The invention makes it possible to strengthen any type of plasma redox effect making the reactive species generated by the plasma and the hydrogen ions interact. By increasing the effectiveness of the plasma treatment, the dose of plasma, for example the duration of its application, can be reduced if desired, thereby reducing its drying nature.

The invention makes it possible by increasing, prolonging and accelerating the redox activities of cold plasma, to increase, prolong and accelerate the antimicrobial activity of cold plasma.

The treated area can be an area of skin, mucous membranes or scalp.

Preferably, the acid composition has a pH between 2 and 5, better between 2.5 and 4. The acid composition is preferably a buffer solution.

[0016] The plasma exposure can be carried out at least 5 min after the application of the composition, to allow it to dry. The exposure to the plasma can take place for less than 30 min, better still less than 15 min after the topical application of the composition. Thus, the skin retains an acidic pH.

The method can include cleaning and drying of said area before applying the composition.

The method may include rinsing the area to which the composition has been applied, after the plasma treatment has been carried out.

The plasma exposure is preferably carried out by moving a plasma generator over the skin. The expression “cold plasma” designates a plasma at atmospheric pressure which does not cause excessive heating of the substrate exposed to the plasma, that is to say a plasma whose average temperature remains close to the initial temperature of the gas ( temperature before the plasma is triggered) and / or close to ambient temperature. A “cold plasma” is also called “non-thermal plasma” or “out of equilibrium plasma”. The plasma can be of the DBD type.

The method according to the invention can be applied to the treatment of healthy skin for the prevention of acne. Within the meaning of the present invention, the term "prevent" means reducing the risk of manifestation of the phenomenon concerned.

The method can also be applied to the scalp, in particular healthy scalp, for the prevention of a dandruff condition.

In another variant, it is used for deodorization, preferably to prevent and / or treat human axillary odors.

More generally, the invention can be applied to prevent and / or treat any disorder, preferably aesthetic, of human keratin materials.

The composition may include citric acid and / or a citric acid salt. Tests have shown that such a composition makes it possible to reduce the pH of the skin sufficiently durably, in particular at least 15 min after application, to allow plasma treatment on the lower pH zone, while having good tolerance.

The method preferably comprises, after plasma treatment, the application of a composition aimed at neutralizing at least partially, better entirely, the acidity provided by the acid composition, and helping the treated area to regain its natural pH.

The invention also relates to an assembly, in particular for the implementation of the method according to the invention as defined above, comprising:

A plasma generator,

An acid composition to be applied to the skin prior to exposure to the plasma, to lower the pH.

The generator and the composition may have all or part of the characteristics stated in connection with the above method. In particular, the plasma generator can be of the DBD type.

A DBD plasma production device is characterized by the presence of an insulating dielectric material between the electrically conductive material of the electrode and the substrate. The presence of this insulating dielectric material prevents the formation of an electric arc during the production of the electric field leading to the plasma, because otherwise all the energy is dissipated in the electric arc and then affects only a small portion gas occupying the space between the electrode and the substrate. The insulating dielectric material, by its position between the electrically conductive material of the electrode and the substrate, will, upon application of the potential difference between the electrically conductive material of the electrode and the substrate, present on the surface a electrical charge :

- negative, resulting from the deposition of electrons, if the dielectric material is associated with the positively charged electrode, or,

- positive, resulting from the deposition of positive ions, if the dielectric material is associated with the negatively charged electrode.

Due to this surface electrical charge, the dielectric material will decrease the intensity of the electric field initially created up to a value causing the plasma to go out. The plasma may be present again when a new discharge can occur, that is to say after elimination of these charges adsorbed on the dielectric material, which is usually achieved by reversing the polarity between the electrodes. The DBD type plasma is then not generated continuously but in the form of point discharges whose frequency will depend on the frequency of an alternating voltage applied to the generator electrode.

The composition can be of pH between 2 and 5, better between 2.5 and 4. The composition can comprise citric acid and / or a citric acid salt.

The whole can be contained in the same packaging device, for example of the box type.

Brief description of the drawings

[Fig. 1] illustrates the application of the acid composition to areas of the face,

[Fig.2] illustrates the plasma treatment of said areas.

detailed description

Illustrated in Figure 1 the application to areas 10 of the skin of the face, other than in sensitive areas 1 and 2 around the mouth and eyes, an acid composition contained in a container 3 , which can be equipped with a metering pump 4. The application can be done by means of a pad 5 or any other suitable applicator.

The acid composition is preferably a buffer solution of pH between 2.9 and 3.6, for example equal to about 3 or 3.5.

The composition may include a weak acid and a salt of this acid, chosen for their good acceptability by the skin. Preferably, the composition comprises citric acid and a citric acid salt, for example trisodium citrate.

For a pH of 3, the acid composition can comprise (by mass) 1.059% of trisodium citrate, 3.455% of citric acid and qs of deionized water, and for a pH of 3.5 1.72% of disodium citrate, 2.973% citric acid and some deionized water.

In Figure 2, there is shown a plasma generator 7 which can be in the form of a portable device held by the user, and moved on each area 10 to be treated, for example according to a scanning movement back and forth, as shown.

The plasma generator 7 has a head 8 which generates a cold plasma and which is moved in contact with the skin. Preferably, the duration of exposure to the plasma per cm ² is between 0.1 s / cm ² and 20 s / cm ² . Preferably, the power density of the plasma is between 0.1W / cm ² and IW / cm ² . Preferably, the temperature of the plasma at the point of application is less than or equal to 60 ° C., better still less than or equal to 40 ° C.

The treated areas are for example a front area 10i, and areas on the cheeks 10 ₂ and 10 ₃ .

The cold plasma generator can be of direct, indirect, hybrid DBD type, jet plasma or plasma needle type or any other type of plasma generator producing cold plasma tolerable by the skin, mucous membranes, scalp or a hair.

The treatment may be aimed at preventing the appearance of acne on healthy skin.

The invention is however not limited to the treatment of acne and can target atopy, bad odors or dandruff. In the latter case, to treat the scalp, the acid composition can be applied in the form of a shampoo or after shampoo.

Plasma treatment can also target cell regeneration, wound healing, obtaining an anti-aging effect, the penetration of active agents by plasma-poration, pigmentation or depigmentation.

Preferably, the acid composition is allowed to dry after its application, for example by waiting 5 min before proceeding to the plasma treatment.

Preferably also, the plasma treatment is applied as soon as possible once the acid composition is dry, so as to benefit as much as possible from the presence of H ⁺ ions, the skin tending to gradually return to its original pH.

Once the plasma treatment has been carried out, it is possible to apply a soothing topical plasma post-treatment formula to limit the drying effects of the plasma and preserve the natural pH of the skin, scalp or hair, which is between 4.5 and 5.

One can also proceed with the application after plasma treatment of a second composition containing active ingredients helping to fight against acne, skin imperfections, atopy, dandruff, bad odors, dehydration of the skin, signs of aging, or active agents acting on the pigmentation or depigmentation of the skin, mucous membranes or hair. Such a cosmetic composition may comprise a compound chosen from: pre-, pro-, post-biotics, plant extracts, antibacterial active agents, antifungal active agents, vitamins, fatty substances and their mixtures.

The plasma generator and the acid composition can be supplied to the user in the form of an assembly within the same packaging, for example a box, case, sachet or blister packaging. If necessary, the assembly comprises a second composition to be applied after plasma treatment, as mentioned above.

If necessary, the plasma generator is equipped with an acid composition applicator for applying the composition to the areas to be treated with plasma.

Although the examples illustrated relate to the first application of a composition for reducing the pH of the skin, it is also possible without departing from the scope of the invention to apply a cold plasma treatment to the skin then the application of a buffer solution at an acidic pH between 2.5 and 5 on the skin, preferably between 3 and 3.5, to lower the pH of the skin and allow the species with longer lifetimes generated by the plasma to react with the acid solution.

Claims (1)

Claims [Claim 1] Together, for the implementation of a process comprising the steps of: (a) applying to an area of human keratin materials to be treated, in particular the skin or the scalp, an acid composition to reduce the pH thereof, (b) subjecting said zone to a plasma treatment, preferably after step a), this set, comprising: A plasma generator (7), the acid composition to be applied to the skin or scalp prior to exposure to plasma, to lower the pH. [Claim 2] Assembly according to the preceding claim, the plasma generator being of the DBD type. [Claim 3] Set according to one of the two preceding claims, the composition being of pH between 2 and 5, better still between 2.5 and 4, in particular between 3 and 3.5. [Claim 4] An assembly according to any one of claims 1 to 3, the composition comprising citric acid and / or a citric acid salt. [Claim 5] Assembly according to any one of claims 1 to 4, comprising a second composition to be applied after the plasma treatment, to neutralize at least partially, better entirely, the acidity provided by the acid composition, and help the treated area to recover its pH natural. [Claim 6] An assembly according to any one of the preceding claims, intended for the treatment of healthy skin for the prevention of acne. [Claim 7] An assembly according to any one of claims 1 to 5, being intended for the treatment of healthy scalp for the prevention of a dandruff condition. 1/1