Rating of butters on TEWL, moisturisation and elasticity

6,7 Much of the information is based upon its composition8,9 or is anecdotal in nature. Nonetheless, most cosmetic chemists are convinced that shea butter works, and works very well, as a moisturiser, improving the lipid barrier function. We believe that many other naturally occurring butters, such as Garcinia Indica Seed Butter (kokum butter), Mangifera Indica (Mango) Seed Butter (mango butter) and Theobroma Cacao (Cocoa) Seed Butter (cocoa butter), may be equal to, or better than, shea butter for reduction in transepidermal water loss (TEWL). A study was therefore undertaken to explore the effects of these butters for cosmetic use on transepidermal water loss, skin moisturisation and skin elasticity. The primary objective of the study was to determine the efficacy of these butters in skin care applications when incorporated in a standard formulation. Of particular interest was performance in comparison to shea butter, an industryrecognised moisturiser. A secondary objective was to determine whether butter performance correlated with aesthetic properties and product preference as assessed by the study subjects. The results would therefore provide guidance in the use of these butters, whether as functional and/or aesthetic equivalents, or in specific applications where their unique performance and/or aesthetic attributes would contribute to desired finished product characteristics. The parameters of interest were measured for test products based on a common formulation base, each containing one of the four butters. Parameters were also measured for a placebo (the common base, without an added butter) and for untreated skin, providing a controlled study from which statistically significant conclusions could be drawn. Measurements were made before application, one hour after application, and eight hours after application of the test products. In addition, aesthetics during and after application to the face were self-assessed by the study subjects. These aesthetic evaluations were not subjected to statistical analysis.
Materials and methods
Testing was performed by Farcoderm Srl, an independent research facility with university affiliation. The aim of the study was to evaluate the effect of four botanical butters for cosmetic use on transepidermal water loss, skin moisturisation and skin elasticity after their first application. Evaluations were made to determine whether product application resulted in:
•  An improvement in the effectiveness of the skin barrier (reduced transepidermal water loss).
•  An increase of the skin elasticity; and/or
•  An increase in skin moisturisation.
Parameters of interest were measured before a single product application, one hour after application, and eight hours after application. The study included a placebo product (no added butter) and an untreated area as well. Products were doubleblind coded so that neither experimenters nor study subjects knew the specific composition under test. The butters subjected to study were formulated without using substances prohibited in cosmetic and body hygiene products (CE legislation). Preserving agents introduced in the formulae can be found in the positive list published by the CE and are used in concentrations conforming to the use set out by this law. In addition, the limits and warnings shown in the respective appendices to regulation 76/768/EEC and subsequent amendments for all substances for which there is a limit of concentration were respected. The raw materials for cosmetic use that were subjected to study were evaluated for safety of use on human volunteers (cosmetic dossier). For instrumental/clinical testing, 2 mg/cm2 of the test products were applied on the study subject’s forearm, both left and right, in accordance with the randomisation scheme of the experimenter. The formulation base is presented in Table 1. The study was carried out in compliance with the following requirements: all twenty subjects participating in the study were selected with the supervision of a dermatologist. Inclusion criteria: healthy female Caucasian subjects, age between 30 and 60 years old, with dry/slightly hydrated skin. Also, an absence of dermatopathies, not undergoing pharmacological treatment (either locally or systemically), and negative anamnesis for atopy. Non-inclusion criteria: subjects who did not fit the inclusion criteria, who had shown allergies or sensitivity to cosmetic products, toiletries, sunscreens and/or topical drugs, or who had dermatological problems on the test area. Study subjects were informed of the aim and the design of the study, made aware of the test procedure and of the possible risk involved in the study execution and gave their informed consent at the beginning of the study. The study subjects’ participation was voluntary. All of the study procedures were carried out in accordance with the ethical principles for the medical research (Ethical Principles for Medical Research Involving Human Subjects, adopted by the 18th World Medical Association General Assembly, Helsinki, Finland, June 1964, and successive amendments). Before the study subjects were exposed to the test products, all relevant safety information about the test products and each ingredient were collected and evaluated. All of the precautions were taken in consideration in order to avoid excessive skin reactions. No such adverse skin reactions were observed.
Evaluation of the skin moisturisation
The measurement of the skin moisturisation is based on the internationally recognised Corneometer method (Courage+Khazaka electronic GmbH). This measurement is based on the dielectric constant of water. The probe shows changes of capacitance according to the moisture content of the measuring object. An electric scatter field penetrates the very first layer of the skin and determines the dielectricity.
Evaluation of transepidermal water loss (TEWL)
Transepidermal water loss is measured by means of the internationally recognised Tewameter method. The instrument used is a Tewameter TM 300 (Courage+Khazaka electronic GmbH). This instrument makes use of Fick’s diffusion law, which is valid within a homogenous diffusion zone, approximately formed by a hollow cylinder. The density gradient is measured indirectly by two pairs of sensors (temperature and relative humidity) and is analysed by a microprocessor. The measuring head of the probe is a narrow hollow cylinder (10 mm diameter and 20 mm height) in order to minimise influences of air turbulence inside the probe.
Evaluation of skin elasticity
Skin elasticity is a measure of the ability of the skin to return to its original rest state following a stressful event and is measured using the Cutometer MPA 580 (Courage+Khazaka electronic GmbH). First, the instrument generates a constant negative pressure (450 mbar), which sucks the skin into the probe during the suction/elongation stage. Then, in the release phase, the pressure inside the probe is taken to zero mbar, allowing the skin to return to the rest stage. The skin reacts to the negative pressure in a biphasic manner characterised by a rapid elongation phase (the elastic component) followed by a second phase in which the skin increasingly resists elongation as it reaches its maximum deformation state (the viscoelastic – mainly plastic – component). A similar biphasic behaviour of the skin is noted when the pressure is released. Initially, the skin tends to return towards its basal state rapidly due to its elastic qualities and then, in the second phase, the plastic component exceeds the elastic component, decreasing the rate of return of the skin towards its original state. When the skin remains in a deformed state, this phenomenon is known as hysteresis. An optical detection system evaluates the depth reached by the skin inside the probe in the two measurement stages. This data is then graphically and numerically reworked to calculate the viscoelastic properties of the skin.
Self-assessment
Study subjects were asked to apply an amount of their choosing of each test product to their faces and to express their personal opinions regarding product characteristics by answering to a questionnaire. Questions covered the topics of post-application skin appearance, skin smoothness, skin softness, skin hydration, skin ‘greasy oily’ sensation, skin ‘sticky’ sensation, test product spreadability, test product texture, test product absorption, test product overall acceptability, and test product preference.
Results and discussion
Mean values were calculated, as were the standard error of the mean and mean percentage variations. Parametric data were subjected to a two-way paired Student’s t-test to determine statistical significance.
Skin moisturisation improvement (Fig. 1)
The untreated skin moisturisation level remained essentially unchanged over the course of the study, attesting to uniform environmental conditions for the duration of the test. The formulation base without added butters was itself moisturising at both one (t1) and eight (t8) hours after application. This is not unexpected given the presence of a light emollient (dicaprylyl carbonate) and a small amount of triglyceride oil (Triticum Vulgare (Wheat) Germ Oil). Practically speaking, this requires a higher level of performance by the butters to achieve moisturisation above that provided by the base. This was indeed the case for all the butters at both t1 and t8, attesting to their superior moisturisation capabilities. While the extent of moisturisation decreased between t1 and t8 for each of the test products, moisturisation remained greater than that prior to treatment (t0). Numerically, kokum butter looks superior to the other butters, especially at t1.
TEWL reduction (Fig. 2)
The rate of transepidermal water loss (TEWL) for untreated skin did not change significantly over the course of the study. The formulation base without added butters produced a significant decrease in TEWL at t1 but not at t8. This is not entirely unexpected given the presence of a light emollient and small amount of triglyceride oil as previously described. Practically speaking, this requires a higher level of performance by the butters, particularly at t1, to achieve TEWL reductions greater than those provided by the base. Only cocoa butter provided a statistically greater reduction in TEWL at t1 than the base, although mango butter contributed directionally to TEWL reduction. Indeed, cocoa butter also performed better than the base with shea butter at t1. By t8, not only the cocoa butter, but kokum butter and mango butter as well, contributed to greater TEWL reductions than the base, attesting to their long term TEWL reduction capabilities.
Elasticity enhancement (Fig. 3)
The elasticity of untreated skin did not change significantly over the course of the study, again suggesting uniform environmental conditions for the duration of the study. The formulation base without added butters produced a significant increase in skin elasticity at t1 which was sustained through t8. Practically speaking, this requires a higher level of performance by the butters to achieve elasticity increases greater than those provided by the base. At t1, both kokum butter and mango butter provided statistically greater increases in skin elasticity than the base. By t8, kokum, cocoa and mango butters provided increases in skin elasticity over that of the base. Numerically, mango butter yielded the greatest increase in skin elasticity, so much so that its performance was better than shea butter’s at both t1 and t8. This attests to mango butter’s superior performance in increasing skin elasticity.
Aesthetic preference (Table 2)
Two of the test products were top rated for multiple attributes. The test product with kokum butter was highest rated for skin softness, lack of ‘greasy oil’ sensation, lack of ‘sticky’ sensation, and enhanced spreadability. The one with mango butter was top rated for skin appearance, smoothness, softness, hydration, texture, and overall acceptability. Cocoa butter and shea butter were not highest rated for any examined attribute. Not unsurprisingly, the base without butters was top rated for product absorption since there was no butter for the skin to absorb. When asked to choose the most preferred product, the one with kokum butter was chosen by twice as many study subjects as that with mango butter, with all others trailing. This indicates that lesser ‘greasy/oil’ and ‘sticky’ sensations and better spreadability are strong factors in product acceptance.
Conclusion
Test products with any of the four butters (cocoa, kokum, mango and shea) significantly reduced transepidermal water loss (TEWL), increased skin elasticity, and increased skin moisturisation, both one hour and eight hours after application. This suggests that any of these butters may be useful in skin care products designed to reduce TEWL and/or increase skin elasticity and moisturisation. The product with cocoa butter was superior to the base (the placebo, without added butter) under all test conditions for the skin moisturisation enhancement and for transepidermal water loss reduction. It also directionally improved skin elasticity at one hour after application, and did so significantly at eight hours after application. So functionally, its performance was superb, but it was not a standout in the area of aesthetics. At least in the base employed for this study, no tested parameters revealed any contribution to superior aesthetics. The product with kokum butter was superior to the base under all test conditions for skin moisturisation and elasticity enhancement. It also reduced transepidermal water loss at eight hours after application. So functionally, its performance was very good. In addition, it contributed outstanding aesthetics to the base, reducing ‘greasy oily’ and ‘sticky’ sensations and providing better spreadability, which proved to be deciding factors in overall test product preference. This suggests that kokum butter is particularly desirable for use in facial care and other products where aesthetics are extremely important. The product with mango butter, like that with kokum butter, was also superior to the base under all test conditions for skin moisturisation and elasticity enhancement and reduced transepidermal water loss at eight hours after application. So functionally, its performance was very good as well. Aesthetically, it was strong in the areas of skin appearance, smoothness, softness, hydration and product texture. Consequently mango butter may prove superior for use in ‘extra moisturising’ formulae for very dry skin (drier than was selected for this study). The product with shea butter proved superior to the base under all test conditions for skin moisturisation. It did not contribute appreciably in the chosen base to transepidermal water loss reduction, nor to enhanced skin elasticity. Given its wide acceptance as a moisturiser, the results of these studies suggest that transition from shea butter to one of the other tested butters could make an already good product even better, functionally and/or aesthetically. For example, the test product with mango butter yielded superior improvement to skin elasticity both one and eight hours after application when compared to that with shea butter. So substituting mango butter for shea butter makes sense when skin elasticity enhancement is a primary focal point for product performance, such as in anti-ageing products. Because the test product with cocoa butter better reduced TEWL than did that with shea butter at one hour after application, substitution of cocoa butter for shea butter may be desirable when a faster acting reduction in TEWL is desired, such as in products intended for quick-acting relief of dry skin.
Acknowledgements
The initial concept and test protocol for this study were developed by Mr Larry Moroni and Mr James Ramirez of the HallStar Company operations in Melbourne, FL, US. An interim protocol and prototype formulations were developed by Dr Edoardo Pallucca and Ms. Carla Filippini of HallStar Italia Srl, with special thanks to Dr Sergio Amari. The final protocol and tests were performed by Farcoderm Srl.
References
1 www.tinyurl.com/b3olru9 (accessed November 2012) 2 www.tinyurl.com/bqeo7zp (accessed November 2012) 3 www.tinyurl.com/bfbtp2w (accessed November 2012) 4 www.tinyurl.com/axawt75 (accessed November 2012) 5 www.tinyurl.com/bhee28r (accessed November 2012) 6 Alander J. Shea butter with improved moisturisation properties. Personal Care 2009; 2 (3): 31-3. 7 Madhuri Reddy P, Gobinath M, Mallikarjuna Rao K, Venugopalaiah P, Reena N. A review on importance of herbal drugs in cosmetics. Int J Adv Pharm Nanotechnol 2011; 1 (3): 133-8. 8 Badifu, GIO. Lipid composition of Nigerian Butyrospermum paradoxum kernel. J Food Compos Anal 1989; 2: 238-44. 9 Maranz S, Wiesman Z, Bisgaard J, Bianchi G. Germplasm resources of Vitellaria paradoxa based on variations in fat composition across the species distribution range. Agroforestry Systems 2004; 60: 71-6.