EP1482907A2

EP1482907A2 - Cosmetic composition that mimics sebum and the use thereof

Info

Publication number: EP1482907A2
Application number: EP02796831A
Authority: EP
Inventors: Philippe Catroux; Nelly Billoni; José Cotovio; Bruno Buan; Gilles Rubinstenn
Original assignee: LOreal SA
Current assignee: LOreal SA
Priority date: 2001-10-30
Filing date: 2002-10-28
Publication date: 2004-12-08
Also published as: WO2003037288A2; WO2003037288A3; US20050175646A1; FR2831442B1; AU2002361306A1; FR2831442A1

Abstract

The invention relates to: a cosmetic composition that mimics sebum; a preparation method thereof; the use of same in cosmetics; the use of same for the preparation of a skin equivalent comprising a sebum equivalent; a skin equivalent comprising a sebum equivalent; and the use of a skin equivalent comprising a sebum equivalent.

Description

Cosmetic composition mimicking sebum, and uses.

The subject of the invention is a cosmetic composition mimicking sebum, a method of preparation, the use in cosmetics of a cosmetic composition mimicking sebum, the use of a cosmetic composition mimicking sebum for the preparation of an equivalent of skin comprising a sebum equivalent, a skin equivalent comprising a sebum equivalent and the use of a skin equivalent comprising a sebum equivalent.

Sebum is a product excreted by the sebaceous glands of the skin of most mammals. The excretion mechanism is a holocrine mechanism by which sebum is deposited on the surface of the skin. One of the roles of sebum is to provide the skin and hair with a hydrophobic coating through the sebaceous canals. In addition, human sebum has unique characteristics compared to that of other mammals. In particular, it contains a very small portion of cholesterol derivatives and a large amount of squalene.

We know the importance of sebum in the homeostasis of the cutaneous tissue: the parts of the human body deficient in sebum (soles of the feet and palms of the hands) reveal a morphology and an esthetic surface of the skin profoundly different from that of the rest of the body. Similarly, in the field of skin care, it appears that certain unsightly inconveniences

(dry skin) as well as major dermatological disorders (premature photoaging) can be attributed to the absence or insufficiency of sebum on the skin surface. However, sebum in some cases (significant photo-oxidative stress, over-proliferation of the bacterial flora ...) is probably a disruptive factor in skin homeostasis, the effects of which are possibly expressed by undesirable side effects in the deep layers of the epidermis. Sebum is particularly present on the face, in the perineal and frontal areas.

It is therefore necessary and always advantageous to be able to have a cosmetic composition mimicking sebum in order to be able to treat the consequences of a deficit in natural sebum.

Moreover, in the field of skin equivalents, to date no model includes an equivalent of sebaceous gland and therefore all existing models have a total absence of sebum.

Again, it turns out to be advantageous to be able to have a cosmetic composition mimicking sebum in order to be able to apply it to a skin equivalent and thus obtain a skin equivalent comprising sebum, skin equivalent which will be even closer to the normal skin than the equivalents currently available.

It is to meet these needs, among other things, that the applicant has developed a cosmetic composition mimicking sebum.

Thus, the subject of the invention is a cosmetic composition mimicking sebum, comprising at least one lipophilic fraction itself comprising at least: from 5% to 20% of squalene, from 50% to 70% of a mixture of triglycerides d linear fatty acids having a chain of 12 to 22 carbon atoms and linear fatty acids having a chain of 12 to 22 carbon atoms, from 15% to 25% of esters of linear fatty acids and fatty alcohols linear having chains of 12 to 22 carbon atoms, from 0.5% to 3% of cholesterol esters, the acid fraction of which comprises a chain of 12 to 22 carbon atoms and from 0% to 5% of cholesterol. it being understood that the ratio between unsaturated fatty chains and saturated fatty chains is between 10 and 0.1.

As linear fatty acid functions, free or in the form of esters, saturated or unsaturated, having a chain of 12 to 22 carbon atoms, there may be mentioned lauric, myristic, palmitic, stearic, arachidic, docosanoic myristoleic, palmitoleic, oleic acids , linoleic, linolenic, γ-linolenic or even arachidonic.

As linear, saturated or unsaturated fatty alcohols having a chain of 12 to 22 carbon atoms, there may be mentioned lauryl, myristilic, cetyl, stearyl alcohols or also oleilic alcohol.

According to a particular form of the invention, the squalene can be in an amount representing from 12% to 18% of the lipophilic fraction.

According to another particular form of the invention, the mixture of triglycerides linear fatty acids having a chain of 12 to 22 carbon atoms and linear fatty acids having a chain of 12 to 22 carbon atoms, may be in an amount representing from 56% to 64% of the lipophilic fraction.

According to yet another form of the invention, the esters of linear fatty acids and of linear fatty alcohols having chains of 12 to 22 carbon atoms can be in an amount representing from 19% to 22% of the lipophilic fraction .

Still according to the invention, the cholesterol esters whose acid fraction comprises a chain of 12 to 22 carbon atoms may be in an amount representing from 0% to 1.5% of the lipophilic fraction.

Finally according to the invention, the cholesterol can be in an amount representing from 1% to 3% of the lipophilic fraction.

Preferably according to the invention, the ratio between unsaturated fatty chains and saturated fatty chains is between 5 and 0.2.

More particularly, the subject of the invention is a cosmetic composition mimicking sebum, characterized in that it comprises at least 12% to 18% of squalene, from 0% to 10% of trimyristine, from 0% to 10% of trimyristoline , from 0% to 10% of tripalmitin, from 0% to 10% of tripalmitoline from 0% to 20% of triolein, from 0% to 10% of tristearin, from 0% to 60% glycerol, from 0% to 15% oleic acid, 0% to 10% palmitic acid, 0% to 15% palmitoleic acid, 0% to 10% myristic acid, 0% to 10% myristoleic acid, 5% to 20% of myristyl oleate, 5% to 10% of palmityl oleate, 0.5% to 3% of cholesteryl palmitate and 0% to 5% of cholesterol. This lipid composition will be such that the sum of the percentages of the free fatty acid fractions added to the sum of the percentages of the triglyceride fractions will be between 55% and 65%. In addition, the ratio between unsaturated fatty chains and saturated fatty chains is between 8 and 0.2.

A very particular composition of the invention is a composition which comprises at least 16% of squalene, 8% of tripalmitine, 18% of tripalmitoline, 12% of trioleine, 10% of oleic acid, 7% of palmitoleic acid, 5 % myristoleic acid, 10% myristyl oleate, 10% palmityl oleate, 1% cholesteryl oleate and 3% cholesterol. This cosmetic composition may contain all the active agents, in particular lipophilic agents, capable of improving or modifying the skin condition. More particularly, the composition of the invention can comprise vitamin E at a concentration of between 0.0025% and 0.01% and preferably between 0.001% and 0.1%.

Another object of the invention is a process for the preparation of a cosmetic composition as described, comprising a first step of weighing each of the ingredients entering into the composition in a sterile container, opaque to light, previously coated with a coating. non-stick, a second step of replacing the air with an inert gas, a third step of raising the temperature to a temperature between 50 ° C. and 100 ° C, preferably between 80 ° C and a fourth step of maintaining the temperature for a time between 25 to 45 minutes, preferably 30 and 40 minutes, with stirring.

Preferably according to the invention, the non-stick coating can be obtained by applying a silane product, particularly a solution of dimethyldichlorosilane in 1, 1, 1 tricholoroethane, very particularly dimethyldichlorosilane at a concentration of between 10g / l and 30g. / l, preferably 20 g / l in 1, 1, 1 tricholoroethane.

According to the invention, the inert gas used in the preparation process can be chosen from argon, nitrogen, neon, krypton, xenon. Preferably we use argon.

The subject of the invention is also a cosmetic composition capable of being obtained by the process which has just been described.

The subject of the invention is also the use of a cosmetic composition as described for overcoming the unsightly inconveniences associated with a sebum deficit, particularly for treating dry skin.

The Applicant has noticed that, surprisingly, the pretreatment with a composition whose fatty phase mimics the properties, chemical and rheological of human sebum, almost completely inhibits the effect of lateral diffusion of cosmetic formulas. The transverse diffusion of the active ingredients and / or components of the formulas applied topically, through the human epidermis has been the subject of numerous studies in the past.

Less known, but nevertheless studied, is the capacity of the superficial organization of the stratum corneum to generate a lateral diffusion of the molecules. The orders of magnitude (distance and speed) conventionally described for this phenomenon are however very small.

Recent work has called the limited nature of this lateral diffusion into question and shown, in the case of clobetasol, that significant quantities of active ingredients could be found, fairly quickly, at macroscopic distances from the point of application.

For those skilled in the art, this is a phenomenon which can prove to be annoying in the case where it is desired to target an active agent (forehead wrinkles and crow's feet, treatment of pigment spots, body treatments. targeted slimming type, high capacity sun filter in highly exposed areas) for maximum efficiency.

To resolve this problem, there is no robust solution listed.

By robust solution is meant a solution which would make it possible to eliminate the phenomenon of lateral diffusion without having to systematically verify or verify by a clinical test the lateral diffusion of the constituents of the formula which is intended for the market and be obliged to modify dramatically the composition of this formula if this effect is observed.

From the above, it is clear that a simple and easy solution to implement to overcome the effect of lateral diffusion would be highly desirable.

However, the Applicant has been able to show that the cosmetic composition mimicking the sebum of the invention has the effect of limiting the lateral diffusion of cosmetic formulas or active agents.

Thus, the invention also relates to the use of a cosmetic composition mimicking sebum, particularly that described above, for controlling the lateral diffusion of cosmetic formulas or active agents.

Preferably, the cosmetic composition mimicking sebum is applied prior to the application of the cosmetic formulas or active agents, in particular on asbogenic (body) or sebogenic areas but cleaned as is the case for example before making up the face. In this particular case, the invention will make it possible to avoid the lateral diffusion of the active agents and pigment contained in makeup products.

The invention therefore also relates to a cosmetic method for limiting the lateral diffusion of cosmetic formulations, characterized in that it comprises a step consisting in applying to the skin, the mucous membranes or the scalp, a composition mimicking sebum such as defined above, and a second step consisting in applying the cosmetic formulation to the zone previously treated with the composition mimicking sebum. The cosmetic formulation may in particular be a cosmetic active agent intended to improve the appearance or the condition of the skin, or a makeup product, intended to color or mask parts of the skin covering.

As we have seen previously, the skin equivalents available are characterized by the absence of sebum or sebum equivalent. It would be particularly interesting, to study the phenomena of sebogenesis and in particular comedogenesis, to have a model of skin reconstructed surface with a lipid composition close to sebum.

Another object of the invention is the use of a cosmetic composition mimicking sebum, particularly that described above, for the preparation of a skin equivalent comprising a sebum equivalent.

Indeed, unexpectedly, the Applicant has found that it is possible to apply compositions mimicking sebum on reconstructed skins in order to obtain physiological or super physiological sebum mimetic rates.

Advantageously, the sebum is applied in the form of a composition obtained by dispersion or of an emulsion of a sebum analog as defined above in a physiological liquid, with a dilution of between 1/50 and 3/20, preferably about 1/20; this dilution being adapted by those skilled in the art depending on the desired end result. Indeed, such formulations can be obtained without adding conventional formulation additives in cosmetics, such as surfactants or preservatives. The subject of the invention is therefore the process for preparing the compositions intended to be applied to the skin equivalents.

By physiological liquid is meant in particular aqueous phases compatible with tissues, such as water, more or less diluted saline solutions such as physiological saline, cell culture and maintenance media, serum, sweat and their mixtures in all proportions.

The composition obtained by diluting the sebum analog is applied to the reconstructed skin, this application being able to be repeated over time, on a regular basis.

The subject of the invention is also a skin equivalent comprising an equivalent of sebum, particularly an equivalent of sebum constituted by the cosmetic composition of the invention.

More particularly, it relates to a skin equivalent comprising on its surface, a sebum equivalent at a concentration of between 0 and 600 μg / cm ² , preferably greater than or equal to 50 μg / cm ² .

The final concentration will be adjusted by a person skilled in the art according to the use of the reconstructed epidermis, it will preferably be less than or equal to 400 μg / cm ² , in particular less than or equal to 300 μg cm ² .

The invention also relates to the use of a skin equivalent comprising a sebum equivalent as described above for studying the interactions between the skin tissue, particularly the epidermis and / or the dermis, and the sebum, particularly in the skin homeostasis.

The invention also relates to the use of a skin equivalent comprising a sebum equivalent as described above for studying the interactions between the skin tissue, particularly the epidermis and / or the dermis, and the sebum after modification of the latter by different exogenous and / or endogenous environmental factors or to assess the efficacy, penetration or toxicity of raw materials and cosmetic formulations.

The Applicant has surprisingly noticed that the repeated treatment of a composition mimicking sebum rich in fatty acids on a reconstructed epidermis model has the effect of gradually thickening the surface layers of the epidermis to the detriment of the deep living layers. The Applicant has been able to show by viability and cell proliferation measures that the effect observed is not due to cytotoxicity. However in the presence of a strong bacterial activity, the triglycerides of sebum are transformed into free fatty acids, known for their comedogenic properties. Under these conditions, one observes at the level of the pilosebaceous channel, a hyperproliferation of keratinocytes of the infrainfundibulum associated with a hypercomification. The Applicant notes an analogy between the natural phenomenon of comedogenesis and that induced on an equivalent of skin comprising an equivalent of sebum rich in free fatty acids.

The Applicant therefore proposes the use of such a biomimetic sebum, enriched in free fatty acids for the preparation of a reconstructed skin model allowing, in particular the evaluation of new substances or combinations of anti-comedogenic substances.

Preferably, in these applications, the percentage of free fatty acids present in the composition mimicking sebum is greater than or equal to 40%.

The subject of the invention is also the use of a skin equivalent comprising a sebum equivalent as described above to study comedogenesis in the presence or in the absence of cosmetic formulas or active agents.

The invention finally relates to a process for preparing a dispersion of the cosmetic composition of the invention, allowing its application both on normal skin and on skin equivalents which comprises a step of dispersing the composition as prepared according to the invention and maintained at a temperature between 50 ° C and 100 ° C, preferably 80 ° C, in a liquid physiological medium, preferably chosen from sweat, physiological saline, a physiological medium containing serum albumin bovine (BSA), skim milk or any other surfactant or a cell culture medium.

A preferred embodiment of the dispersion according to the invention consists in a light opaque flask previously coated with a non-stick coating, to weigh a desired amount of artificial sebum, to add a desired amount of physiological liquid medium, to heat at a temperature between 50 ° C. and 100 ° C, preferably at 80 ° C, for a time between 10 seconds and one minute, preferably 20 seconds, pass the flask through an ultrasonic bath for a time between 10 seconds and 2 minutes, preferably 30 seconds and then shake with a vortex for a time between 5 seconds and one minute, preferably 10 seconds.

Preferably according to the invention the desired quantities of artificial sebum and of liquid physiological medium are such that the application of 2 μl of the dispersion provides the skin with the physiological quantity necessary, namely 10O μg of sebum.

Indeed, one of the advantages of the invention is to allow the delivery to the skin of a physiological amount of sebum, that is to say for normal skin between 100 to 200 μg / cm ² , which, to the knowledge of Applicant is not realized in the solutions proposed by the prior art.

The following examples illustrate the invention without limiting it in any way. In these examples, reference is made to the appended figure, representing the influence of the quality of sebum on an Episkin model.

Example 1: formulation of sebum:

The following cosmetic composition mimicking the sebum S1 is produced. The amounts are given as a percentage of the total weight of the composition: squalene 16% tripalmitin 8% tripalmitoline 18% triolein 12% oleic acid 10% palmitoleic acid 7% myristoleic acid 5% myristyl oleate 10% palmityl oleate 10% cholesteryl oleate 1% cholesterol 3%

In an amber glass vial with a previously silanized screw (Repel Silane, Dimethyldichlorosilane solution, 20g / l in 1, 1, 1, -trichloroethane, Pharmacia Biotech No 17-1331-01) and autoclave, weigh the various ingredients used in the composition sebum S1, add a magnetic bar and fill the flask with an inert argon-type gas to avoid any peroxidation of the ingredients in the air. Place the sebum in a heating bath at 80 ° C and with stirring for 30 to 40 minutes until a perfectly clear liquid is obtained.

Precautions:

The reconstituted sebum solidifies after 10 minutes at room temperature, so it is necessary to keep it in a water bath at 80 ° C until the dispersion is prepared. The sebum is kept under Argon.

Example 2: Preparation of the dispersion: In a previously silanized amber flask, 10 mg of artificial sebum S1 of Example 1 are weighed, then 200 μl of DMEM / F12 culture medium 1: 1 is added (Eagle medium modified by Dulbecco / Mixture nutrient-F12). The flask is then heated in a water bath at 80 ° C for 20 seconds, and then passed into an ultrasonic bath for 30 seconds and finally stirred with a vortex for 10 seconds.

The desired amount of artificial sebum S1 can then be applied to the skin (normal or artificial) by spreading using a spatula.

The dispersed form has the advantage of allowing the application of physiological amount of artificial sebum, ie between 100 to 200 μg / cm ² .

Example 3: Lateral diffusion effect for two cosmetic formulas:

The effect of diffusion of the formulas is estimated on the forearm of voluntary subjects. The formulas are applied up to 2mg.cm ^"1. The application surface is a rectangle of 4cm by 7cm (28cm ² are therefore treated) whose length is positioned in the axis of the arm. After 1 hour, the strip stripping method (Wigman, H. et al., (1999) Skin Pharmacopoeia. Apple. Skin Physiol. 12, 46-53.5) is evaluated, the residual amount of butylmethoxydibenzoylmethane in the central part and the part which has migrated more 3mm from the edges of the rectangle.

Result: on the treated forearm, there is, on average 82% of butylmethoxydibenzoylmethane applied in the central part for formula I and 69% for formula II. At the same time, the quantity of butyl methoxydibenzoylmethane which can be taken from the upper or lower end of the rectangle (relative to the arm) on surfaces of 1.9 cm x 4 cm, placed 3mm from the application area is 0.8% for formula I and 7.6% for formula II.

Compositions of formulas I and II: The quantities are given as a percentage by weight of the total weight of the composition

Formulas I II

PEG-100 Stearate 0.75 0.75

Glyceryl Stearate 0.75 0.75

Palmitic Acid 1, 21 1, 21

Myristyc Acid 0.0825 0.0825

Stearic Acid 1, 4575 1, 4575

Cetyl Alcohol 0.5 0.5

Dimethicone 0.5 0.5

C12-15 Alkyl Benzoate 8.5 20.0

Butyl Methoxydibenzoylmethane 3.72 3.72

Methylparaben 0.174 0.174

Butylparaben 0.042 0.042

Propylparaben 0.021 0.021

Isobutylparaben 0.021 0.021

Phenoxyethanol 0.7 0.7

Ethylparaben 0.042 0.042

Triethanolamine 0.45 0.45

Glycerin 5.0 5.0

Potassium Cetyl Phosphate 1, 0 1, 0

Carbomer 0.3 0.3

Octocrylene 10.0 -

Water QSP QSP

100% 100%

Example 4 Effect of the pre-treatment with the sebum S1 of Example 1 on the lateral diffusion of the formula II:

The protocol of Example 3 is repeated with formula II. 1 hour before the application of formula II, a suspension of sebum S1 from Example 1 at 5% in an aqueous 0.9% NaCl solution is applied to the right forearm (forearm left as a witness), so that a measurement at sebumeter (MONADERM ™) indicates an application of 200μg.cm ^"2. The surface of application of sebum S1 is a rectangle whose center is identical to that of application of the formulas (example 3) and whose length and width are 2 cm higher than the latter (i.e. a 6 x 7 cm rectangle).

Results: under these conditions, on the forearm pre-treated with sebum S1, the amount of butylmethoxydibenzoylmethane found in the central part is 94% (compared to 69% without pretreatment) and the amount of butylmethoxydibenzoylmethane that can be removed on the upper or lower end of the rectangle (relative to the arm) on surfaces of 1.9 cm x 4 cm, placed 3 mm from the application area is lowered to 0.7% (compared to 7.6%) .

Note that the amount of sebum S1 actually applied in this example (≈200μg.cm ^'2 ) is analogous to the amount of sebum naturally found on the surface of the face (anatomical area, naturally seborrheic) of individuals with normally oily skin. This does not mean, however, that individuals with oily skin would not be affected by the phenomenon of lateral diffusion since facial care products are, in general, applied to a clean and therefore defatted face.

EXAMPLE 5 Influence of the Quality of Sebum on a Model of Reconstructed Skin

We apply to a reconstructed skin model Epskin® compositions progressively enriched in free fatty acids, to obtain a comedogenesis model.

The figure in the appendix shows the changes in the proliferation / differentiation balance on day 13.

These photos illustrate the differences in morphologies presented by a reconstructed skin model (Episkin®) progressively enriched in free fatty acids ((from 0% fatty acids (photo left end) to 60% free fatty acids (photo right end) )) and gradually depleted in triglycerides (from 60% to 0%). The sebum rich in triglycerides promotes the maintenance and the appearance of the granular layer, the sebum rich in fatty acids leads to the thickening of the stratum corneum. of a composition mimicking sebum rich in fatty acids has the effect of gradually thickening the surface layers of the epidermis to the detriment of the deep living layers. The thickening of the epidermis is observed from a sebum composition comprising 40% fatty acids. morphological change induced in vitro presents an analogy with the natural phenomenon of comedogenesis. In vivo, a hyperproliferation of the keratinocytes of the infrainfundibulum associated with hypercomification is observed in the pilosebaceous canal.

Claims

1. Cosmetic composition mimicking sebum, comprising at least one lipophilic fraction itself comprising at least: from 5% to 20% of squalene, from 50% to 70% of a mixture of triglycerides of linear fatty acids having a chain from 12 to 22 carbon atoms and linear fatty acids having a chain from 12 to 22 carbon atoms, from 15% to 25% of esters of linear fatty acids and linear fatty alcohols having chains from 12 to 22 carbon atoms, from 0.5% to 3% of cholesterol esters, the acid fraction of which comprises a chain of 12 to 22 carbon atoms and from 0% to 5% of cholesterol. it being understood that the ratio between unsaturated fatty chains and saturated fatty chains is between 0 and 0.1.

2. Composition according to the preceding claim, characterized in that the squalene is in an amount representing from 12% to 18% of the lipophilic fraction.

3. Composition according to any one of claims 1 or 2, characterized in that the mixture of triglycerides of linear fatty acids having a chain of 12 to 22 carbon atoms and linear fatty acids having a chain of 12 to 22 carbon atoms, are in an amount representing from 56% to 64% of the lipophilic fraction.

4. Composition according to any one of claims 1 to 3, characterized in that the esters of linear fatty acids and linear fatty alcohols having chains of 12 to 22 carbon atoms are in an amount representing from 19% to 22% of the lipophilic fraction.

5. Composition according to any one of claims 1 to 4, characterized in that the cholesterol esters whose acid fraction comprises a chain of 12 to 22 carbon atoms are in an amount representing from 0% to 1.5% of the lipophilic fraction.

6. Composition according to any one of claims 1 to 5, characterized in that the cholesterol is in an amount representing from 1% to 3% of the lipophilic fraction.

7. Composition according to any one of claims 1 to 6, characterized in that the ratio between unsaturated fatty chains and saturated fatty chains is between 5 and 0.2.

8. Cosmetic composition mimicking sebum, characterized in that it comprises at least 12% to 18% of squalene, from 0% to 10% of trimyristine, from 0% to 10% of trimyristoline, from 0% to 10% of tripalmitin, from 0% to 10% of tripalmitoline from 0% to 20% of triolein, from 0% to 60% of glycerol, from 0% to 10% of tristearin, from 0% to 15% of oleic acid, of 0% to 10% palmitic acid, 0% to 15%> palmitoleic acid, 0% to 10% myristic acid, 0% to 10% myristoleic acid, 5% to 20% of myristyl oleate, from 5% to 10% of palmityl oleate, from 0.5% to 3% of cholesteryl palmitate and from 0% to 5% of cholesterol, it being understood that the sum of the percentages of the free fatty acid fractions added to the sum of the percentages of the triglyceride fractions will be between 55% and 65% and that the ratio between unsaturated fatty chains and saturated fatty chains is between 8 and 0.2.

9. Cosmetic composition mimicking sebum, characterized in that it comprises at least 16% of squalene, 8% of tripalmitine, 18% of tripalmitoline, 12% of trioleine, 10% of oleic acid, 7% of palmitoleic acid , 5% myristoleic acid, 10% myristyl oleate, 10% palmityl oleate, 1% cholesteryl oleate and 3% cholesterol.

10. Cosmetic composition mimicking sebum according to any one of claims 1 to 9, characterized in that it also comprises vitamin E at a concentration between 0.0025% and 0.01% and preferably between 0.001% and 0.1% .

11. A process for preparing a cosmetic composition as described in any one of claims 1 to 10, comprising a first step of weighing each of the ingredients entering into the composition in a container ^• sterile, opaque to light, prior coated with a non-stick coating, a second step of replacing the air with an inert gas, a third step of raising the temperature to a temperature of 50 ° C. and 100 ° C, preferably 80 ° C. and a fourth step of maintaining the temperature for a time between 25 to 45 minutes, preferably 30 and 40 minutes, with stirring.

12. The method of claim 11, the inert gas is selected from argon, nitrogen, neon, krypton, xenon.

13. Method according to the preceding claim, characterized in that the inert gas is argon.

14. Cosmetic composition according to any one of claims 1 to 10 capable of being obtained by the process of any one of claims 11 to 13.

15. Use of a composition according to any one of claims 1 to 10 and 14 to alleviate the unsightly inconveniences linked to a sebum deficit.

16. Use according to the preceding claim for treating dry skin.

17. Use of a composition according to any one of claims 1 to 10 and 14 for controlling the lateral diffusion of cosmetic formulas or active agents.

18. Use according to the preceding claim, characterized in that the composition is applied prior to the application of the cosmetic formulas or active agents.

19. Use of a composition as described in any one of claims 1 to 10 and 14 for the preparation of a skin equivalent comprising an equivalent of sebum.

20. Skin equivalent including an equivalent of sebum.

21. Skin equivalent according to the preceding claim, characterized in that the sebum equivalent is a cosmetic composition as described in any one of claims 1 to 10 and 14.

22. Use of a skin equivalent comprising a sebum equivalent to study the interactions between the sebum, the epidermis and or the dermis, particularly in cutaneous homeostasis.

23. Use of a skin equivalent including a sebum equivalent for study the interactions between the skin tissue, ^{'particularly} the epidermis and / or dermis, and sebum after modification of the latter by various environmental factors exogenous and / or endogenous.

24. Use of a skin equivalent comprising a sebum equivalent to evaluate the efficacy, penetration or toxicity of raw materials and cosmetic formulations.

25. Use of a skin equivalent comprising a sebum equivalent to study comedogenesis in the presence or absence of cosmetic formulas or active ingredients.

26. A method of preparing a dispersion of the cosmetic composition of the invention comprising a step of dispersing the composition as prepared according to the invention and maintaining it at a temperature between 50 ° C and 100 ° C, preferably 80 ° C, in a liquid physiological medium.

27. The method of claim 26, characterized in that the liquid physiological medium is chosen from sweat, physiological serum, or even a cell culture medium.

28. Method according to any one of claims 26 or 27, characterized in that the desired quantities of artificial sebum and of physiological liquid medium are such that the application of 2 μl of the dispersion provides the skin with the physiological quantity necessary, namely 100 μg sebum.