FUNDAMENTOS: Os cosméticos hidratantes melhoram a pele, aproximando-a de suas condições ideais, pois aumentam a quantidade de água no estrato córneo. As vitaminas A e E, bem como as ceramidas, são substâncias ativas que vêm sendo muito empregadas em hidratantes, os quais constituem uma das mais importantes classes de produtos cosméticos e de higiene corporal. OBJETIVO: - O objetivo deste trabalho foi avaliar o efeito no pH cutâneo da pele humana de uma emulsão O/A (constituída de base auto-emulsionante não iônica) acrescida, ou não, de vitamina A palmitato ou vitamina E acetato ou ceramida III, por metodologia não invasiva MÉTODOS:O estudo foi realizado em 40 mulheres com idade entre 30 e 45 anos, empregando-se o equipamento Skin Phmeter PH 900 PC. As medidas foram efetuadas no antebraço das voluntárias nos tempos de sete e 30 dias após auto-aplicação diária (duas vezes ao dia), dos produtos envolvidos no estudo RESULTADOS E CONCLUSÃO: A presença das vitaminas A ou E, ou da ceramida não alterou de maneira significativa o pH da pele, o que mostra que as formulações estudadas são adequadas para o uso cosmético.
lipídios; vitamina A; vitamina E
BACKGROUND: Moisturizers are believed to improve the skin's condition by increasing the water content of the stratum corneum. Vitamins A and E and ceramides have been widely used in cosmetic moisturizing products, and these are one of the most important cosmetic and body care products. OBJECTIVE: The aim of this research was to evaluate the effects on the pH of human skin of an O/W emulsion (non ionic self-emulsifying base) with and without vitamin A palmitate, or vitamin E acetate, or ceramide III, using a non-invasive method. METHOD: The investigations were carried out on a group of 40 healthy female test subjects aged between 30 and 45 years old, using the Skin pH meter PH 900 PC. The measurements were performed on the forearm of volunteers at 7 and 30 days after daily use (twice a day) of the products used in the study. RESULTS AND CONCLUSION: The presence of vitamins A or E or ceramide III did not change the pH of the skin, consequently the formulations studied are suitable for cosmetic usage.
lipids; vitamin A; vitamin E
CLINICAL, LABORATORY AND THERAPEUTIC INVESTIGATION
Study of pH variation on the skin using cosmetic formulation s with and without vitamins A, E or ceramide: by a non-invasive method* Correspondence Profa Dra. Gislaine Ricci Leonardi Rua Floriano Peixoto 1630 ap101 Piracicaba SP 13400 520 Tel.: (19) 3434-1537 E-mail: email@example.com
Gislaine Ricci LeonardiI; Lorena Rigo GasparII; Patrícia M. B. G. Maia CamposIII
IPharmacist, Masters and Ph.D., FCFRP-USP, Professor of the Pharmacy Course and Coordinator of the Cosmetology Specialization and Manipulation Magisterial at the Methodist University of Piracicaba - UNIMEP
IIPharmacist, FCFRP-USP, Masters and Ph.D., FCFRP-USP
IIIPharmacist - FCFRP-USP, Masters and Ph.D. - FCF-USP and Professor of Cosmetology at FCFRP-USP
Correspondence Correspondence Profa Dra. Gislaine Ricci Leonardi Rua Floriano Peixoto 1630 ap101 Piracicaba SP 13400 520 Tel.: (19) 3434-1537 E-mail: firstname.lastname@example.org
BACKGROUND: Moisturizers are believed to improve the skin's condition by increasing the water content of the stratum corneum. Vitamins A and E and ceramides have been widely used in cosmetic moisturizing products, and these are one of the most important cosmetic and body care products.
OBJECTIVE: The aim of this research was to evaluate the effects on the pH of human skin of an O/W emulsion (non ionic self-emulsifying base) with and without vitamin A palmitate, or vitamin E acetate, or ceramide III, using a non-invasive method.
METHOD: The investigations were carried out on a group of 40 healthy female test subjects aged between 30 and 45 years old, using the Skin pH meter PH 900 PC. The measurements were performed on the forearm of volunteers at 7 and 30 days after daily use (twice a day) of the products used in the study.
RESULTS AND CONCLUSION: The presence of vitamins A or E or ceramide III did not change the pH of the skin, consequently the formulations studied are suitable for cosmetic usage.
Key words: lipids; vitamin A; vitamin E.
Moisturizers constitute one of the most important classes of cosmetic and body hygiene products since they are widely used for both preventative action (against xeroderma and in the retardation of precocious aging) as well as for their usefulness in supporting dermatological therapeutics in a considerable variety of cutaneous dysfunctions.1
The addition of active substances into many cosmetic formulations used to moisturize skin has become a very frequent practice.
The use of ceramides in cosmetic products has also been growing recently since the endogenous ceramides, which are part of the lipid mantle of the skin, act by retaining water in the corneum stratum and thereby helping to maintain the skin hydrated.2-7
Among other active substances much used in skin care today, are vitamins A and E.8-12 Vitamin E has stood out in anti-aging formulations, because, besides its humectant property, it is also a potent neutralizer of free radicals.13 Likewise, vitamin A has been reported as an activate substance for anti-aging purposes.14-15
Demonstration of the effectiveness of the active substances used in cosmetic products, as well as the effects caused by the formulations in human skin, have been the subject of study among the scientific community. Such research results in technical and scientific progress within the cosmetic sector that is developing more and more and winning space in this epoch in which quality of life has become a major objective.
Research into cosmetology has been growing more and more, due to the contribution and partnership of several areas of the basic and applied sciences, including pharmacology, dermatology, histology, anatomy, physiology, microbiology, chemistry and physics.16
In the last few decades we have witnessed an explosion of information and scientific progresses related to cutaneous research, which has benefited both dermatologists and professionals that work with the development of cosmetic products.17-18
Before the use of noninvasive techniques, dermatology and similar areas were based, essentially, on clinical observation alone, which due to its subjective nature could be considered a somewhat imprecise method. However, following technological progress the noninvasive methodologies have appeared, which are scientifically proven and non traumatic, without involving any aggression or discomfort to either patients or volunteers participating in the studies. The application of these methodologies has been revolutionizing the cosmetic sector, since they have enabled a quantitative analysis and better still have scientifically demonstrated the beneficial effects of the cosmetic products.18
In the last twenty years, equipment offering a wide application (for cosmetology, aesthetic medicine and dermatology) has become available, thus giving rise to new noninvasive methodologies for cutaneous research.19-33
An example of such apparatus is the Phmeter", which evaluates the superficial pH of the skin.
The determination of the pH of the cutaneous surface, or that is the hydrogen ionic concentration, has been the subject of much research. The pH of the cutaneous surface is seen by some authors as an important functional indicator of the skin, since it arises from the production of lactic acid which confers the so-called "cutaneous acid mantle".34
Healthy skin presents a slightly acid pH (4.6 - 5.8), which contributes to the bactericidal and fungicidal protection of its surface. Furthermore, the cutaneous secretions present an appreciable buffering capacity; an important property since the pH of the skin is frequently altered as a consequence of the use of inappropriate topical products, thereby exposing the skin to a series of aggressive agents and especially microorganisms.35-37
Hence, determination and control of cutaneous pH, from the cosmetic and/or dermatological point of view, are of extreme usefulness since contact with aggressive substances, such as detergents can be frequent and also in order to avoid the use of inadequate topical products.35
Regarding the techniques developed for pH determination, measurements using a potentiometer have gained a particular emphasis, this is performed with several types of electrode: hydrogen, quinhydrone and antimony.18With the Phmeter", analysis of the pH of the cutaneous surface is made by direct potentiometry, or that is, through a special electrode.36
Direct potentiometry has been the method of choice for measurement of this variable and allows sensitivity in the order of 0.1 of the pH unit.37
In view of the above, the objective of this work was to evaluate the effect on the cutaneous pH of human skin of O/A emulsions with and without the addition of vitamin A palmitate, vitamin E acetate or ceramide III, using noninvasive methodology.
For this study an O/A emulsion was used comprising: 17% nonionic self-emulsifying wax; 3% squalene; 0.5% imidazolydinyl urea; 0.2% methylparaben; 0.1% propylparaben; 10% glycerin; 0.3% glutathione; 0.04% DL-alpha tocopherol; and distilled water. This formulation (considered to be the vehicle) was tested with and without the addition of vitamin A palmitate (5,000UI/g) or vitamin E acetate (20mg/g) or ceramide III (1mg/g).
Evaluation of cutaneous pH
The study protocol was approved by Committee of Ethics in Research of the Hospital das Clínicas, Faculty of Medicine of Ribeirão Preto, University of São Paulo (FMRP-USP) and was conducted in 40 women after informed consent, with age ranging from 30 to 45 years and skin type II, III or IV.
The volunteers that participated were neither using medication nor presented dyschromia at the time of the study. Having read and understood the Term of Informed Consent, they declared that they fully agreed in participating in the research and were aware of the procedures, risks and benefits, among other related factors.
The study was performed using Skin pH meter PH 900 PC apparatus, which measures the cutaneous pH. The measurements were taken in the volunteers' forearm, on day seven and 30 after self-application (twice a day) of the products in question. The application area was duly cleaned with distilled water and cotton and, shortly afterwards, dried with a paper towel 30 minutes before the reading.
To determine the pH of the corneum stratum three measurements were made at the study venue and the results were presented as mean values of these sequential measurements.
The volunteers' left forearm was treated with the various formulations. The 40 volunteers were divided into five groups of eight women each. Group 1 used a formulation without any active substances (or in other words, only the vehicle selected for evaluation). The remainder used this vehicle with several substances added: Group 2, 0.5% vitamin A palmitate; Group 3, 2% vitamin E acetate; Group 4, 0.1% ceramide III, and finally the Control Group which used nothing on the skin.
A fixed quantity of the sample was applied to the skin of the volunteer's forearm and distributed in circular movements for 15 seconds.
The entire test was conducted in a room with controlled temperature (between 20 and 22°C) and relative humidity (50 to 60%).
The study was performed using a statistical software package (GMC program) elaborated by Maia Campos,39 and the results statistically analyzed by variance analysis.
RESULTS AND DISCUSSION
The results of the cutaneous pH for the different formulations used in the study are summarized in table 1.
The results of the preliminary tests indicated that the sample was reasonably homogeneous and the distribution of frequencies was very close to the distribution of frequencies of the normal mathematics, which indicated the use of parametric statistics in the data analysis.
The most appropriate parametric test for the mathematical model of this experiment was variance analysis and since this was a mixed model, in which a factor with independent variation was at the same time associated to a linked factor, variance analysis using the partition data technique was employed.
The results of the test for variance analysis are shown in table 2.
As can be seen in table 2, the variance analysis demonstrated that there was no statistically significant difference in the cutaneous pH in relation to the time periods studied in this work. It can be concluded, therefore, that the time factor did not influence the pH of the human skin. The statistical analysis also demonstrated no statistically significant difference in the pH of the skin when comparing the formulation (vehicle) and addition of the active substances involved in the study.
From the above results, it was verified that there was no statistically significant difference between the factors studied (time, active substance, presence or not of active substance in the vehicle). In other words, the presence or absence of the various active substances studied (vitamin A palmitate, vitamin E acetate and ceramide III) in the cosmetic vehicle and in the time periods analyzed, did not cause a significant alteration in the pH of the skin, thereby demonstrating that the formulations studied are appropriate for cosmetic usage.
The authors extend their thanks to Prof, Dr Ana Maria Ferreira Roselino, M.D. dermatologist at FMRP-USP, for her valuable suggestions.
Received in August, 31th of 2001.
Approved by the Consultive Council and accepted for publication in April, 16th of 2002.
*Work done at "Faculdade de Ciências Farmacêuticas de Ribeirão Preto da Universidade de São Paulo"
- 1. Rodrigues L, Pinto P, Silva N, Galego N, Quaresma P, Fitas M, Pereira LM. Caracterização da eficácia biológica de hidratantes por análise dinâmica do conteúdo hídrico epidérmico e profilometria de transmissão luminosa. Cosmet Toiletr 1997; 9 (2): 44-9.
- 2. Gray GM, White RJ. Glycosphingolipids and ceramids in human and pig epidermis. J. Invest Dermatol 1978; 70: 336.
- 3. Wertz PW, Miethke MC, Long AS, Strauss JS, Downing DT. The composition of the ceramides from human stratum corneum and from comedons. J Invest Dermatol 1985; 84: 410.
- 4. Imokawa G, Akasaki S, Kawamata A, Yano S, Takaishi N. Water - relation function in the stratum corneum and its recovery properties by synthetic pseudoceramides. J Soc Cosm Chem 1989; 40: 273-85.
- 5. Rieger M. Skin constituents as cosmetic ingredients. Cosmet Toiletr 1992; 107 (11): 85-94.
- 6. Bahia MFG, Santos D. Promotores para ação epidérmica e anexial. Cosmet Toiletr 1996; 8 (6): 33-9.
- 7. Rieger M. Ceramides: their promise in skin care. Cosmet Toiletr 1996; 111 (12): 33-45.
- 8. Saperstein H, Rapaport M, Rietschel RL. Topical vitamin E as a cause of erythema multiforme-like eruption. Arch Dermatol 1984; 120: 906-8.
- 9. Kazumaro F. Vitamin E: biological and clinic aspects of topical treatment. Cosmet Toiletr 1987; 102 (11): 99-115.
- 10. Hermitte R. Aged skin, retinoids and alphahydroxyacids. Cosmet Toiletr 1992; 107 (7): 63-7.
- 11. Mayer P. The effects of vitamin E on the skin. Cosmet Toiletr 1993; 108 (2): 99-109.
- 12. Maia Campos P.M.B.G, Ricci G, Semprini M, Lopes RA. Histopathological, morphometric and stereologic studies of dermocosmetic skin formulations containing vitamin A and/or glycolic acid. J Cosmet Sci 1999; 50 (3): 159-70.
- 13. Pugliese PT. Antioxidantes, envelhecimento e a pele. Rev Cosmiatr Med Est 1998; 6 (1): 25-7.
- 14. Idson B. Vitamins and the skin. Cosmet Toiletr 1993; 108 (2): 79-94.
- 15. Leonardi GR, Maia Campos PMBG. Vitamina A e seus derivados. Rev Cosmiatr Med Est 1997; 5 (4): 24-7.
- 16. Smith WP, Calvo L. Cosméticos hoje. Cosmet Toiletr 1991; 3 (5): 24-31.
- 17. Leonardi GR, Maia Campos PMBG. Penetração cutânea. Cosmet Toiletr 1997; 9 (4): 34-5.
- 18. Rodrigues, L. Bioengenharia cutânea: metodologias não invasivas de abordagem da pele. Rev. Cosmiatr Med Est 1997; 5 (2): 26-35.
- 19. Tagami H, Ohi M, Iwatsuki K, Kanamaru Y, Yamada M, Ichijo B. Evaluation of the skin surface hydration in vivo by eletrical measurement. J Invest Dermatol 1980; 75 (6): 500-7.
- 20. Blichmann CW, Serup J. Assessment of skin moisture. Acta Dermatol Venereol 1988; 68: 284-90.
- 21. Frodin T, Helander P, Molin L, Skogh M. Hydration of human stratum corneum studied in vivo by optothermal infrared spectrometry, eletrical capacitance measurement, and evaporimetry. Acta Dermatol Venereol 1988; 68: 461-7.
- 22. Obata M, Tagami H. Electrical determination of water content and concentration profile in a simulation model of in vivo stratum corneum. J Invest Dermatol 1989; 92: 854-9.
- 23. Pinnagoda J, Tupker RA, Coenraads PJ, Nater JP. Comparability and reproducibility of the results of water loss measurements: a study of 4 evaporimeters. Contact Dermatitis 1989; 20: 241-6.
- 24. Serup J, Winther A, Blichman W. Effect of repeated application of a moisturizer. Acta Dermatol Venereol 1989; 69: 457-9.
- 25. Obata M, Tagami HA rapid in vitro test to assess skin moisturizers. J Soc Cosmet Chem 1990; 41 (4): 235-41.
- 26. Lodén M, Lindberg M. The influence of a single application of different moisturizers on the skin capacitance. Acta Derm Venereol 1991; 71: 79-82.
- 27. Schrader K, Bielfeldt S. Comparative studies of skin roughness measurements by image analysis and several in vivo skin testing methods. J Soc Cosmet Chem 1991; 42 (6): 385-91.
- 28. Watanabe M, Tagami H, Horri I, Takahashi M, Kligman AM. Functional analyses of the superficial stratum corneum in atopic xerosis. Arch Dermatol 1991; 127 (9): 1689-92.
- 29. Kumasaka KH, Takahashi K, Tagami H. Eletrical measurement of the water content of the stratum corneum in vivo and in vitro under various conditions: comparasion between skin surface hygrometer and corneometer in evaluation of the skin surface hydratrion state. Acta Dermatol Venereol 1993; 73: 335-9.
- 30. Serup J. Bioengineering and the skin: from standard to error to standard operating procedure. Acta Dermatol Venereol 1994; Suppl.185: 5-8.
- 31. Tagami H. Quantitative measurements of water concentration of the stratum corneum in vivo by high-frequency current. Acta Derm Venereol 1994; Suppl. 185: 29-33.
- 32. Sun B K, Lee HK, Cho JC, Kim JI. Clinical improvement of skin aging by retinol containing products: with non-invasive methods. In: Congresso Latino Americano e Ibérico de Químicos Cosméticos, 13. Anais. Acapulco, Sociedade Mexicana de Ciências Cosméticas, 1997: 37-45.
- 33. Kuss O, Diepgen TL. Proper statistical analysis of transepidermal water loss (TWEL) measurements in bioengineering studies. Contact Dermatitis 1998; 39: 64-7.
- 34. Zlotogorski A. Distribution of skin surface pH on the forehead and cheek of adults. Arch Dermatol Res 1987; 279: 398-401.
- 35. Rodrigues L. A avaliação biofísica da superfície cutânea: indicadores fisiológicos da funcionalidade epidérmica. Rev Port Farm 1995; 45 (1): 52-9.
- 36. Rodrigues L. Bioengenharia cutânea: novas perspectivas sobre a fisiologia da pele. Cosmet Toiletr 1996: 8 (4): 51-5.
- 37. Pinto P, Galego N, Silva N, et al Definição de critérios de avaliação dos efeitos sobre a superfície cutânea de cremes hidratantes: I - análise após uma aplicação. Rev Port Farm 1997; 47 (1): 23-34.
- 38. Rodrigues L. A avaliação biofísica da superfície cutânea: princípios e metodologias. Rev Port Farm 1995; 45 (1): 11-21.
- 39. Maia Campos G. G.M.C. Software versão 7.0. Ribeirão Preto, Departamento de Estomatologia - Faculdade de Odontologia de Ribeirão Preto - USP, 1998.
Publication in this collection
12 May 2006
Date of issue
16 Apr 2002
31 Aug 2001