WO2023242527A1 - Iontophoretic method for administering mandelic acid - Google Patents

Abstract

The invention relates to an iontophoretic cosmetic and non-therapeutic method for delivering mandelic acid, to a cosmetic composition suitable for an iontophoretic method comprising mandelic acid and to a kit comprising said composition.

Description

Iontophoretic method of administering mandelic acid

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of skin care.

Iontophoresis is an active technique which improves the passage of certain molecules into or through the skin using a low electric current (<1 mA). An iontophoretic device consists of a power source and at least two electrodes. One electrode is active, as the current entry point, the other is passive, as the current exit point. One electrode is then the anode, preferentially connected to the positive pole, while the other is the cathode, preferentially connected to the negative pole. The main mechanisms of iontophoresis are:

• Electro-migration or electro-repulsion: the electric current causes the ions to migrate according to their charge. A positively charged molecule in a formulation placed under the anode (+) will be repelled towards the skin and will be attracted to the electrode (-). On the contrary, a negatively charged molecule in a formulation placed under the cathode (-) will be repelled towards the skin and will be attracted by the electrode (+);

• Electro-osmosis or convective transport: allows the transport of molecules thanks to the movements of the solvent from the anode towards the skin and from the skin towards the cathode. This flow is possible thanks to the negative charges of the skin at physiological pH.

Many active molecules in skin care compositions are in ionic form, therefore iontophoresis can be an effective tool for the delivery of these active molecules.

Mandelic acid is the aromatic alpha-hydroxy acid (AHA) with the largest molecular size. Its penetration into the skin is less significant than other AHAs.

It is necessary to increase the penetrated quantity and release kinetics of mandelic acid and improve the release rate into the skin, compared to topical application. SUMMARY OF THE INVENTION

A first subject of the invention relates to a cosmetic and non-therapeutic iontophoretic process for delivering a cosmetic active ingredient through the skin comprising the following steps:

• Apply to the skin a composition comprising mandelic acid and one or more cosmetically acceptable additives,

• Apply simultaneously, successively or sequentially over a certain time range a direct current, pulsed current or a combination of the two from a device comprising at least one electrode applied to the skin, so as to improve the transport of mandelic acid through the skin.

A second subject of the invention relates to a cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives.

A third object of the invention relates to an iontophoretic kit comprising:

• Cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives, and

• An iontophoretic device for implementing the process according to the invention.

FIGURES

[Fig. 1]: diagram of an iontophoresis device according to one embodiment

[Fig. 2]: diagram of an iontophoresis device according to another embodiment

[Fig. 3]: discontinuous current density waveform for iontophoresis

[Fig. 4]: diagram of the principle of iontophoretic transport

[Fig. 5]: photographs of the electrodes used in the examples (left: flexible electrodes, center: V1 tip, right: V2 tip)

[Fig. 6]: photograph of the assembly

[Fig. 7]: annotated photograph of the comparison montage of the broadcast

[Fig. 8]: comparison diagram of the cutaneous diffusion of mandelic acid contained in the study gel

[Fig. 9]: comparison diagram of the cutaneous diffusion of the mandelic acid contained in the study formula between passive diffusion and iontophoresis with the V1 tip

[Fig. 10]: comparison diagram of the cutaneous diffusion of mandelic acid contained in the study formulas between passive diffusion and iontophoresis with the V2 tip DETAILED DESCRIPTION OF THE INVENTION

Non-therapeutic cosmetic process

A first subject of the invention relates to a cosmetic and non-therapeutic iontophoretic process for delivering a cosmetic active ingredient into the skin, comprising:

• Apply to the skin a composition comprising mandelic acid and one or more cosmetically acceptable additives;

• Apply simultaneously, successively or sequentially over a certain time range a direct current, pulsed current or a combination of the two from a device comprising at least one electrode applied to the skin, so as to improve the transport of mandelic acid through the skin.

The process which is the subject of the invention can use a composition comprising mandelic acid as defined below.

The method according to the invention can be applied to any biological subject, in particular mammals, preferably human beings.

Fluent

The current applied must not cause discomfort, risk of injury or side effects to the user. It is therefore necessary to ensure that the strength of the current and the shape of the electrical wave are bearable throughout the duration of the treatment. In certain cases, a discontinuous current can help avoid the risk of discomfort.

In certain embodiments of the iontophoresis process, the applied current is preferably continuous, with an average current density of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably of 0.01 mA/cm ² to 0.4 mA/cm ² , and more preferably from 0.05 mA/cm ² to 0.3 mA/cm ² .

In certain embodiments of the iontophoresis process, the applied current is preferably discontinuous, with an average current density of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably of 0.01 mA/cm ² to 0.4 mA/cm ² , more preferably 0.05 mA/cm ² to 0.3 mA/cm ² and particularly preferably 0.13 mA/cm ² to 0.45 mA/cm ² . In certain embodiments of the iontophoresis process, the applied current is discontinuous with an average current density of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably 0.01 mA/cm ² to 0, 4 mA/cm ² , and more preferably from 0.05 mA/cm ² to 0.3 mA/cm ² .

Preferably, the average intensity of the current is between 0.001 mA and 0.5 mA and is for example of the order of 0.1 mA.

In some embodiments of the iontophoresis method, direct current and discontinuous current are applied in combination, preferably with the above current densities.

“Discontinuous current” or “pulsed current” means a current whose intensity varies over time.

By direct current we mean a current whose intensity does not vary over time, that is to say that the intensity is constant and is independent of time.

In some embodiments of the iontophoresis method, the applied discontinuous current has sinusoidal waveforms, non-sinusoidal waveforms, or combinations thereof.

In some embodiments of the iontophoresis method, the discontinuous current applied has periodic square waveforms, rectangular waveforms, sawtooth waveforms, spike waveforms, trapezoidal waveforms, triangular waveforms, or combinations thereof.

Preferably, the discontinuous current applied has rectangular waveforms, advantageously with an average intensity of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably of 0.01 mA/cm ² to 0.4 mA/ cm ² , and more preferably from 0.05 mA/cm ² to 0.3 mA/cm ² .

In some embodiments of the iontophoresis method, the current is applied for 30 seconds to 120 minutes, preferably 2 minutes to 50 minutes and more preferably 3 minutes to 40 minutes. In some embodiments, the direct current stimulus may be applied for a duration of 2, 5, 10 or 20 minutes.

Figure 3 illustrates an embodiment of representative current density waveform electrical stimuli generated by the circuitry of the iontophoresis device.

Referring to Figure 3, a first current density waveform is illustrated for iontophoresis. Figure 3 illustrates an embodiment of a waveform that can be generated by the circuit and the iontophoresis device of Figure 1 or 2.

Figure 3 illustrates a discontinuous current waveform stimulus having a rectangular wave profile. The average intensity of this current is of the order of 0.1 mA. The maximum intensity of this current is around 0.2 mA. Each 0.2 mA current pulse is applied for approximately 40 ms, then no current is applied for another 40 ms period, and so on. The current frequency is around 12.5 Hz.

The current density and duration values illustrated in Figure 3 are given as an example and are not limiting.

Cosmetic composition suitable for iontophoresis

A second object of the invention relates to a cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives.

By “cosmetic composition adapted to an iontophoretic process”, we mean that the active principle included in the composition, in this case mandelic acid, is in a sufficiently ionized form, so that the application of a current to the skin to which the composition is applied allows the electromigration of the mandelic acid, in other words the transport of the mandelic acid through the skin.

dans laquelle [A ] et [AH] représente les concentrations respectives des formes base conjuguée et acide de l’acide mandélique. By “sufficiently ionized”, we mean that the percentage of ionization of the mandelic acid within the composition is typically at least 80%, preferably at least 90%. The ionization percentage depends mainly on the pH of the composition. It can be calculated using the following Henderson-Hasselbach equation:

in which [A] and [AH] represent the respective concentrations of the conjugated base and acid forms of mandelic acid.

Assets

Mandelic acid is an alpha hydroxy acid (AHA) extracted from bitter almonds.

Mandelic acid has the formula:

Its pKa is 3.4 and its molecular weight is 152.15 Da.

Due to these physicochemical properties (water-soluble and ionizable molecule at a pH between 4 and 6.5), mandelic acid is a good candidate for iontophoresis.

At a pH below 4, the ionization percentage of mandelic acid in water is less than 80%. In a pH range from 4 to 6.5, the ionization percentage of mandelic acid in water varies from 80% to 100% respectively. In particular, in a pH range going from 4.5 to 6.5, the percentage of ionization of mandelic acid in water changes respectively from 93% to 100%, and in a pH range going from 5 .5 to 6.5, the ionization percentage of mandelic acid in water changes respectively from 99% to 100%. The charged active ingredient (-) will be repelled by the electrode (-) to penetrate the skin in greater quantities compared to passive diffusion.

Advantageously, the composition comprises from 0.001 to 25.0% by weight relative to the total weight of the composition, preferably 0.1 to 10.0% by weight of mandelic acid. In some embodiments, the composition comprises 1 to 10% by weight of acid mandelic, in particular from 2 to 10% by weight. In other embodiments, the composition comprises 0.3 to 2.0 weight percent mandelic acid.

The pH of the composition is notably higher than the pKa of the mandelic acid, so that the mandelic acid is in sufficiently ionized form. The composition can have a pH varying from 4 to 8, preferably from 4.5 to 7. The pH of the composition can be adjusted by adding a base or an acid according to any method known to those skilled in the art, for example by adding sodium hydroxide.

Advantageously the pH of the composition varies from 4 to 6.5, preferably from 5.5 to 6, so that the composition is both suitable for an iontophoretic process and compatible for application to the skin.

The amount of mandelic acid in the composition influences the pH of the composition. Indeed, mandelic acid, by definition, acidifies the composition and will therefore reduce its pH. Advantageously, the composition comprises a quantity of mandelic acid less than or equal to 10% by weight relative to the total weight of the composition, preferably a quantity of mandelic acid between 1 and 10% by weight, so as to maintain a pH ranging from 4 to 8, in particular from 4 to 6.5, more particularly from 5.5 to 6, without it being necessary to add an acid or a base to adjust the pH.

Additives

The composition may further comprise one or more polar solvent(s) compatible for application to the skin, preferably present in an amount of at least 30% by weight, preferably in an amount of at least 40% by weight, and more preferably in an amount of at least 50% by weight, relative to the total weight of the composition. The polar solvent(s) are for example chosen from water and alcohols, such as ethanol.

The composition may further comprise one or more anionic or nonionic polymers present in quantities ranging from 0.01% to 30% by weight, preferably from 0.1% to 10% by weight, relative to the total weight of the composition. . The anionic polymer(s) are for example chosen from nucleic acid derivatives, proteins, polypeptides and polysaccharides, such as polyglutamate, alginate, pectin or hyaluronic acid. The composition may further comprise one or more gum(s) chosen from the group consisting of xanthan gum, Caesalpinia spinosa gum (tara or carob gum from Peru) and Sclerotium rolfssii gum.

Advantageously, the composition comprises 0.3 to 3.0% by weight, preferably 0.4 to 2.0% by weight, preferably 0.4 to 1.5% by weight and more preferably 0 .5 to 1.0% by weight of Caesalpinia spinosa gum (tara gum or Peruvian carob) relative to the total weight of the composition. Advantageously, the composition comprises at most 0.6% by weight of Caesalpinia spinosa gum (tara gum or Peruvian carob) relative to the total weight of the composition.

Advantageously, the composition comprises from 0.1 to 1.3% by weight, preferably from 0.2 to 1.1% by weight, preferably from 0.3 to 0.9% by weight and preferably from 0. .3 to 0.8% by weight of Sclerotium rolfssii gum relative to the total weight of the composition. Advantageously, the composition comprises a maximum quantity of Sclerotium rolfssii gum and Caesalpinia spinosa gum less than or equal to 1.0% by weight relative to the total weight of the composition.

Advantageously, the composition comprises a ratio of Caesalpinia spinosa gum (tara gum or Peruvian locust bean): Sclerotium rolfssii gum by weight ranging from 1:5 to 5:1, preferably from 1:2 to 2:1.

In a preferred embodiment, the composition comprises:

- from 0.5 to 1.0% by weight of Caesalpinia spinosa gum (tara gum or Peruvian carob) relative to the total weight of the composition and for example 0.6% by weight;

- from 0.3 to 0.8% by weight relative to the total weight of the composition of the gum of Sclerotium rolfssii and for example 0.3% by weight; in which the sum of the proportions of Caesalpinia spinosa gums and Sclerotium rolfssii is at most 1.0% by weight relative to the total weight of the composition.

A composition according to this embodiment advantageously has excellent stability. The composition may comprise water present in an amount of at least 30% by weight, in particular in an amount of at least 60% by weight, and more preferably in an amount of at least 80% by weight, relative to the total weight of the composition.

The composition is, for example, free of any ionizable preservative.

The composition may further comprise one or more texturizing agents chosen from the group consisting of Glucomannan, cellulose derivatives such as Hydroxypropyl Methylcellulose, gums such as xanthan.

In known manner, the dosage forms dedicated to topical administration can also contain conventional adjuvants in the cosmetic and/or dermatological field.

The composition may further comprise one or more selected multi-functional ingredients selected from the group consisting of, non-ionic Pentylene glycol, 1,2 hexanediol, Gaprylyl glycol, Propanediol and O-Cymen-5-ol. These ingredients, generally at a concentration of no more than 15% by weight relative to the total weight of the composition, make it possible to reinforce the antimicrobial properties of the final product.

Galenic

Such a composition may be in the form of an aqueous, hydroalcoholic solution, a solution or dispersion of lotion or serum type, an emulsion of liquid or semi-liquid consistency of milk type, obtained by dispersing a fatty phase in an aqueous phase (OÀV) or vice versa (W/O), or a suspension, or emulsion, of soft, semi-solid or solid consistency, of the cream, aqueous or anhydrous gel type, a microemulsion, a microcapsule, a microparticle, or a vesicular dispersion of ionic and/or non-ionic type.

These compositions are prepared according to the usual methods known to those skilled in the art.

Route of administration

A composition according to the invention is advantageously administered topically to the skin. It can be used for cosmetic and/or dermatological treatment of the skin.

Iontophoresis kit

The invention also provides an iontophoresis kit comprising:

• Cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives, and

• An iontophoretic device to implement the process as described above.

The iontophoresis composition may be as described above.

The selected current profile may be as described above in relation to the method.

In certain embodiments, the kit according to the invention is in the form of a tube (or container) comprising the cosmetic composition according to the invention and an electronic cap comprising said iontophoretic device to implement the method as described above.

Iontophoretic device

With reference to Figure 1, an iontophoresis device 1 and a set of electrodes 41, 2, 43 are illustrated schematically. In this embodiment, the iontophoresis device 1 comprises an electronic plug 4 advantageously connected to a tube 2, containing a cosmetic composition, in particular such as that described above. The electronic plug 4 is preferably assembled on the tube 2 in a reversible manner, in particular by screwing. This allows the user to easily change the tube 2, and therefore to change composition and cosmetic treatment, while retaining a single electronic cap 4. For example, the user could thus have in his possession a single cap electronic 4 and different tubes 2, for example a first tube with the mandelic acid composition defined previously, a second tube with another composition suitable for iontophoretic use, etc. It will then be possible and easy for the user to alternate between the different cosmetic compositions in order to benefit from different cosmetic treatments on the skin.

By electronic plug 4 is meant any electronic and/or electrical and/or electromechanical device capable of generating a current, in particular a current such as that described previously and illustrated in Figure 3. The electronic plug 4 is designed to be placed in contact with the user's skin during treatment, in particular via the electrodes 41, 42, 43. Preferably, the electronic plug 4 is designed to be mounted reversibly, in particular by screwing, on the tube 2 containing the cosmetic composition.

According to another embodiment of the iontophoretic device 1 illustrated in Figure 2, the device further comprises a cannula 3, disposed between the electronic plug 4 and the tube 2. This cannula 3 is designed to, on the one hand, be mounted on the tube 2 preferably in a reversible manner, for example by screwing, and on the other hand, pass through the electronic plug 4, as can be seen in Figure 2. The cannula 3 can be designed to cooperate with the electronic plug according to the principle of a pivot connection. This cannula 3 then makes it possible to convey the cosmetic composition from tube 2 to the user's skin without coming into contact with the electronic cap 4, thus preserving the electronic components of the latter, improving hygiene and facilitating cleaning. of the last.

According to one embodiment, the iontophoretic device 1 is produced in accordance with that described in the patent application filed by the applicant under the filing number FR2200962.

Whatever the embodiment of the iontophoretic device 1, the electronic plug 4 notably comprises a power source (not shown), such as a cell or a rechargeable battery, a current waveform generator (not shown). ), a first electrode (active) 41, a second electrode (counter or return) 42. The device can also include other electrodes and other elements (such as a light-emitting diode for example) without departing from the scope of the invention .

In the illustrated embodiments, the electronic cap also includes an orifice 44 designed to deliver the cosmetic composition to the user's skin, in particular following the pressure that the user will exert on the tube 2 during the treatment.

In the embodiment where the electronic cap 2 comprises a cannula 3 (Figure 2), the latter is connected in a sealed manner to the orifice 44, so that the cosmetic composition contained in the tube 2 is delivered directly to the skin of the the user, passing through the electronic cap 2 without however coming into contact with the internal components (in particular electronic and/or electrical) of the latter. The objective of Figures 1 and 2 is to illustrate and describe some of the main functional components of an iontophoresis device used to carry out one or more of the various embodiments of the methods described herein.

The circuits used to perform the functions of the iontophoresis device are implicit, inherent and well known to those skilled in the art so that they will not be described in further detail here.

In certain embodiments, the iontophoresis device is packaged in the form of a manual device which can be carried in one hand during treatment, as is particularly the case with the embodiments illustrated in Figures 1 and 2 Treatment with a handheld device includes constantly moving the iontophoresis device over the skin such that at least the active electrode 41 is moved over the skin surface while making contact. Preferably it is the electronic cap 4 and tube 2 assembly, that is to say the entire iontophoretic device 1, which is moved by the user on his skin, as the iontophoretic treatment progresses. We could also imagine, without departing from the scope of the invention, that the iontophoretic device 1 is moved by a first user on the skin of a third party user, for example in the case of a cosmetic treatment carried out in a beauty institute. .

A suitable power source is any power source capable of generating electrical current to power the various other circuits and devices. In certain embodiments, a battery, preferably rechargeable, is used as a power source. In some embodiments, the iontophoresis device is plugged into a wall outlet. In some embodiments, the power source produces direct current.

In some embodiments, an iontophoresis device includes an iontophoresis patch model. By iontophoresis patch we mean any device intended to be applied to a specific area of the skin and to remain immobile there for at least a certain time so as to carry out localized and continuous iontophoresis treatment. In an illustrative and non-limiting manner, the patch could be produced such as that described in the applicant's patent published under the number FR 3 035 792 and/or FR 3 034 017. In some embodiments, an iontophoresis device includes an iontophoresis face mask design. By facial mask we mean any device intended to be applied to a large area of the skin, such as the forehead and/or cheeks, around the eyes, the neck, and to remain immobile there for at least a certain time so as to to carry out a continuous iontophoresis treatment over the entire said area. By way of illustration and not limitation, the patch could be produced such as that described in the applicant's patent application published under number WO 2017/212343.

Cosmetic applications

In a preferred embodiment, the above method makes it possible to reduce spots on the hands and/or on the face and/or on the neck and/or décolleté, for example age spots and/or sun spots. and/or freckles and/or spots due to disease. Then, the above method allows depigmentation of the skin, especially in areas where the pigmentation is initially too high. After several uses or a single use of the method of the invention, the color of the skin is more uniform and the homogeneity is increased.

In another embodiment, the method is used to treat signs of aging, to improve skin smoothness, skin quality and appearance.

In another embodiment, the method is used to minimize signs of skin aging, and/or pigmentation, and/or volume, and/or sagging of wrinkles, and/or tone and/or wrinkles. spots, and/or to improve the firmness, and/or radiance, and/or smoothness of the skin. The method of the invention can be associated with the application of active agents associated with an electric current, in particular a microcurrent).

Mandelic acid is known for:

• Accelerate the rate of cell renewal.

• Rid the skin of dead cells.

• Improve dull complexion.

Mandelic acid is multifunctional, thanks to the following properties:

• Inhibitor of tyrosinase activity - thus reducing the production of melanin in the skin, reduces hyperpigmentation spots.

• Peeling -removes dead skin cells and evens out skin tone.

• Antibacterial, by reducing the presence of Gram bacteria - improves the texture and appearance of acne-prone and comedogenic skin.

• Antiseptic. EXAMPLES

Material and method

Depending on the studies carried out, different types of electrodes are used as presented below.

Soft electrodes

Flexible electrodes (Àg/ÀgCl coated with carbon) are used as part of the study in static mode (see Figure 5).

For viscous formulations, the deposits are applied directly to the electrodes using a mold.

For low viscosity formulations, the deposits are made on a non-woven support previously fixed on the electrodes using an adhesive film.

Stainless steel electrodes integrated into an applicator tip

These electrodes are used as part of the study in dynamic mode, that is to say, a circular movement of the tip is made on the skin covered with the formula studied. The use of stainless steel electrodes in dynamic mode makes it possible to get closer to the final use of the product by the consumer. This makes it possible to validate the proof of concept of the association of the tips with the active. Two different tips are used: the V1 tip and the V2 tip (see Figure 5).

Cellules de diffusion The detailed description of the different electrodes used is presented below.

Diffusion cells

The diffusion cells comprise skin explants in a housing.

This study is carried out on porcine ear skin explants.

Porcine ear skin has the most similarities with human skin in terms of skin thickness, follicular structure, vascular anatomy and arrangement of collagen fibers.

Example 1: study of the iontophoretic effectiveness of mandelic acid (MA)

This study is carried out with flexible electrodes.

The diffusion cells are placed in a water bath at 37°C to obtain a temperature of 32°C on the surface of the skin.

They are connected to a current generator (see Figure 6).

In this study, we compare diffusion with cells connected to electrodes (AD) to diffusion with unconnected cells (passive diffusion SD) (see Figure 7).

We thus calculate an improvement factor directly linked to iontophoresis which is equal to the average of the concentrations of the active ingredient in the skin for the AD samples divided by the average of the concentrations of the active ingredient in the skin for the SD samples. .

This report indicates the degree of improvement in the skin passage of the active ingredient by iontophoresis (AD) compared to passive application (SD).

La formule testée (« Gel d’étude n° 1 ») a la composition suivante.

The study is carried out under the following experimental conditions.

The tested formula (“Study Gel No. 1”) has the following composition.

Results

Figure 8 presents the comparison of the average of the areas of the mandelic acid peaks measured at the cathode of the cells with devices (ÀD -) compared to the average of the areas of the mandelic acid peaks measured in the control cells without device (SD ).

The average of the ÀD - areas is 4.1 times greater than the average of the SD (control) areas. Consequently, iontophoresis makes it possible to very clearly improve the diffusion of mandelic acid compared to passive diffusion.

Example 2: study of the iontophoretic effectiveness of the V1 tip with a formula comprising mandelic acid

This study is carried out with the V1 tip.

The study is carried out under the following experimental conditions.

The tested formula (“Glowing Pen” cream) has the following composition.

Results

Figure 9 presents the comparison of the average of the areas of the mandelic acid peaks measured at the electrode of the cells with the study cream and having been treated by iontophoresis with the V1 tip (ÀD) compared to the average of the areas mandelic acid peaks measured in control cells with passive diffusion (SD).

The average of the ÀD - areas is 2.08 times greater than the average of the SD areas. Consequently, the V1 tip improves the skin absorption of the mandelic acid contained in the cream used.

Example 3: study of the iontophoretic effectiveness of the V2 tip with two formulas comprising mandelic acid

This study is carried out with the V2 tip.

The study is carried out under the following experimental conditions.

Résultats The composition of the “Glowing Pen” cream is indicated in the previous example. The tested serum has the following composition.

Results

Figure 10 presents the comparison of the average area of the mandelic acid peaks measured at the electrode of cells with serum and cream and having been treated with iontophoresis with the V2 tip (ÀD) compared to the average peak areas of mandelic acid measured in control cells with passive diffusion (SD).

The average area ÀD - is 1.67 times greater than the average area SD for cream and 3.82 times greater for serum. Consequently, the V2 tip makes it possible to increase the skin diffusion of mandelic acid whatever the formulation used.

Example 4: Study of the solubility of mandelic acid in water

Tests: Visual solubilities carried out at pH 5.5 +/- 0.1

TÀ= ambient temperature (20° C +/- 2°)

Example 5: study of the stability of a composition according to the invention

The stability of compositions according to the invention was evaluated at 4°C, at room temperature and at 40°C, by observation of physicochemical characteristics (pH, viscosity, visual appearance) over time, at 0 days, 1 month and 3 months. In particular, the compositions described in Examples 1 and 2 with 0.6% by weight of tara gum and 0.3% by weight of sclerotium rolfssii gum showed excellent stability after 3 months at the three temperatures tested.

Claims

1. Cosmetic and non-therapeutic iontophoretic process for delivering a cosmetic active ingredient through the skin comprising the following steps: • Apply to the skin a composition comprising mandelic acid and one or more cosmetically acceptable additives, • Apply simultaneously, successively or sequentially over a certain time range a direct current, pulsed current or a combination of the two from a device comprising at least one electrode applied to the skin, so as to improve the transport of mandelic acid through the skin. 2. Method according to claim 1, in which a direct current is applied having an average current density of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably of 0.01 mA/cm ² to 0.4 mA/cm ² , and more preferably from 0.05 mA/cm ² to 0.3 mA/cm ² . 3. Method according to claim 1, in which a discontinuous current is applied having an average current density of 0.001 mA/cm ² to 0.5 mA/cm ² , preferably of 0.01 mA/cm ² to 0.4 mA/cm ² , and more preferably from 0.05 mA/cm ² to 0.3 mA/cm ² . 4. Method according to claim 3, wherein a discontinuous current is applied having an average current density of 0.13 mA/cm ² to 0.45 mA/cm ² . 5. Method according to any one of the preceding claims, in which a direct current is applied for from 30 seconds to 120 minutes, preferably from 2 minutes to 50 minutes and even more preferably from 3 minutes to 40 minutes. 6. Method according to any one of the preceding claims, in which the composition comprises from 0.001 to 25.0% by weight, preferably from 0.1 to 10.0% by weight of mandelic acid relative to the total weight of the composition. 7. Method according to any one of the preceding claims, said composition comprising a gum chosen from the group consisting of xanthan gum, Caesalpinia spinosa gum (tara gum or Peruvian locust bean) and Sclerotium rolfssii gum. 8. Method according to claim 7, in which the composition comprises from 0.3 to 3.0% by weight, preferably 0.4 to 2.0% by weight, preferably from 0.4 to 1.5% by weight. weight and preferably from 0.5 to 1.0% by weight of Caesalpinia spinosa gum (tara gum or Peruvian carob) relative to the total weight of the composition. 9. Method according to claim 7 or 8, in which the composition comprises from 0.1 to 1.3% by weight of Sclerotium rolfssii gum relative to the total weight of the composition, preferably from 0.2 to 1.1 % by weight, preferably 0.3 to 0.9% by weight and preferably 0.3 to 0.8% by weight. 10. Method according to any one of claims 7 to 9, in which the composition comprises a ratio of Caesalpinia spinosa gum (tara gum or Peruvian carob): Sclerotium rolfssii gum by weight ranging from 1:5 to 5:1, of preferably 1:2 to 2:1. 11. Method according to any one of the preceding claims, in which the composition has a pH varying from 4 to 8, preferably 4.5 to 7, preferably 4.5 to 6.5. 12. Cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives. 13. Cosmetic composition according to claim 12, comprising 0.001 to 25.0% by weight, preferably 0.1 to 10.0% by weight of mandelic acid relative to the total weight of the composition. 14. Cosmetic composition according to claim 12 or 13, comprising a gum chosen from the group consisting of xanthan gum, Caesalpinia spinosa gum (tara gum or Peruvian locust bean), Sclerotium rolfssii gum. 15. Cosmetic composition according to claim 14, comprising from 0.3 to 3.0% by weight, preferably 0.4 to 2.0% by weight, preferably from 0.4 to 1.5% by weight and preferably from 0.5 to 1.0% by weight of Caesalpinia spinosa gum (tara gum or Peruvian carob) relative to the total weight of the composition. 16. Cosmetic composition according to claim 14 or 15, comprising from 0.1 to 1.3% by weight of Sclerotium rolfssii gum relative to the total weight of the composition, preferably from 0.2 to 1.1% by weight , preferably from 0.3 to 0.9% by weight and more preferably from 0.3 to 0.8% by weight. 17. Cosmetic composition according to any one of claims 14 to 16, said composition comprising a ratio of Caesalpinia spinosa gum (tara gum or Peruvian carob): Sclerotium rolfssii gum by weight ranging from 1:5 to 5:1, preferably from 1:2 to 2:1. 18. Cosmetic composition according to any one of claims 12 to 17, having a pH varying from 4 to 8, preferably 4.5 to 7, preferably 4.5 to 6.5. 19. Iontophoretic kit comprising: • A cosmetic composition suitable for an iontophoretic process comprising mandelic acid and one or more cosmetically acceptable additives, and • An iontophoretic device for implementing the method according to any one of claims 1 to 9. 20. Kit according to claim 19, in the form of a tube comprising a container comprising said cosmetic composition and a cap comprising said iontophoretic device for implementing the method according to any one of claims 1 to 11.