Skinification

on

Skin care

KEYWORDS

Sensitive skin ,

Hair care,

Scalp,

Biophysics,

Skinification,

Skin barrier.


peer-reviewed

Expanding sensitive skincare to the scalp:
​​​​​​​an example from a topical serum against sensitive scalp symptoms

CYRIL MESSARAA1*; LAURANNE SOUCI2, CAMILLE MENY2, PEDRO CONTREIRAS PINTO3
*Corresponding author
1. C’kin Matters, Kallithea, Greece
2. Lazartigue, Paris, France
3. PhD Trials,Lisbon, Portugal

ABSTRACT: Pruritus is prevalent among the population, with the scalp regarded as one of the most affected zones. The objective was to design and test a formulation for people experiencing regular skin discomfort on the scalp. Hallmarks of sensitive skin such as skin hydration, skin barrier, skin itching and skin redness were measured on the scalp before and up to 21 days of use. Skin hydration and skin barrier on the scalp were improved after a single use while itching intensity and scalp redness were reduced in the short and long term. By alleviating the burden of sensitive skin, these results are an example of “Skinification” of scalp care, where benefits traditionally expected for facial skin are expanded to other body parts.

“

“A study in healthy women providing probiotic yogurt for four weeks showed an improvement in emotional responses as measured by brain scans”

Figure 1. Skin Section with Microbiome. Most microorganisms live in the superficial layers of the stratum corneum and in the upper parts of the hair follicles. Some reside in the deeper areas of the hair follicles and are beyond the reach of ordinary disinfection procedures. There bacteria are a reservoir for recolonization after the surface bacteria are removed.

Materials and methods

Studies of major depressive disorder have been correlated with reduced Lactobacillus and Bifidobacteria and symptom severity has been correlated to changes in Firmicutes, Actinobacteria, and Bacteriodes. Gut microbiota that contain more butyrate producers have been correlated with improved quality of life (1).


A study in healthy women providing probiotic yogurt for four weeks showed an improvement in emotional responses as measured by brain scans (2). A subsequent study by Mohammadi et al. (3) investigated the impacts of probiotic yogurt and probiotic capsules over 6 weeks and found a significant improvement in depression-anxiety-stress scores in subjects taking the specific strains of probiotics contained in the yogurt or capsules. Other studies with probiotics have indicated improvements in depression scores, anxiety, postpartum depression and mood rating in an elderly population (4-7).


Other studies have indicated a benefit of probiotic supplementation in alleviating symptoms of stress. In particular, researchers have looked at stress in students as they prepared for exams, while also evaluating other health indicators such as flu and cold symptoms (1). In healthy people, there is an indication that probiotic supplementation may help to maintain memory function under conditions of acute stress.

INTRODUCTION

INTRODUCTION

Recent insights on the latest hair care spending showed that while anti-ageing products (e.g. hair loss, hair dyes) remain the key focus of consumers, scalp health is receiving greater attention (1). Among these concerns, pruritus or itching is most commonly reported on the scalp compared to other body sites and is most intense at night (2). Furthermore, skin conditions such as dandruff and seborrheic dermatitis, often characterized by itching, are mostly prevalent on the scalp (3).


According to the literature, reactive or sensitive skin is characterized by several attributes. Firstly, it is frequently associated with skin barrier defects (4), primarily because more permeable skin would react more readily to external stimuli and generate discomfort. It has been shown that the skin barrier of sensitive skin subjects is easier to disrupt (5). Sensitive skin is also characterized from a neuronal perspective, with an overexpression of sensory receptors activated by heat, low pH, mechanical stress, UV, etc. One of the most discussed channels in the literature is Transient Receptor Potential Vallinoid 1 (TRPV1), whose expression correlates with the intensity of sensitive skin symptoms (6). A vascular component appeared to be associated with sensitive skin subjects, who exhibited both a higher density of blood vessels and closer proximity to the epidermis compared to subjects with normal skin, which would explain the higher prevalence of face flushing for the formers (7).


Still, literature concerning the sensitive skin on the scalp is far less abundant compared to the sensitive skin on the face or body. A first study conducted on 1011 French women in 2008 reported an incidence sensitive scalp of 44.2%, and heat, pollution, emotions and shampoos as the main triggers (8). In another study conducted on 133 women aged 18-65 years, sensitive skin on the scalp correlated with sensitive skin on the body. Itching was the first symptom, followed by tingling and tightness. The severity of the scalp sensitivity was not correlated to menstrual status, age, tobacco consumption, body mass index, skin type or phototype. As for cosmetics consumption, no evidence was seen between the frequency/quantity of shampoo versus the severity of sensitive skin, as opposed to conditioners. The authors suggested taking a closer look at ingredients commonly used in the latter (9). In a study conducted on Korean women, subjects with sensitive scalps were found to have a higher average temperature, increased heat sensation, dandruff, and erythema in the scalp compared to those with non-sensitive scalps (10). More recent research, conducted worldwide on 50552 adults from 20 countries, found a prevalence of sensitive scalps between 35% and 60% depending on the country. Incidence was higher in younger volunteers aged 16-44 years (50.9%) compared to those aged 45-64 years (44.3%) and over 65 years (39.7%) (11). From a microflora perspective, recent work described that sensitive scalps may exhibit specific patterns. While there were notable changes in the fungal communities, there was minimal difference in the distribution of bacteria between sensitive and healthy scalps of a Chinese cohort (12).


Like sensitive skin, triggers can be intrinsic or extrinsic: cosmetics usage, variations in temperature, cold, heat, wind, sun, air conditioning, wet air and dry air, water, exposure to pollution or psychological stress-related (13). Often used in the treatment of androgenic alopecia, topical minoxidil has been reported as a trigger of sensitive scalp, especially when formulated with propylene glycol or alcohol (14).


Over the last few years, the hair care offer has become more sophisticated and diverse, with a greater emphasis on scalp care driven by the demand from Asian Pacific countries (15). Thus the scalp is a suitable target for “skinification”, meaning that this body part should receive the same level of care as the face. In practice, this implies transposing technologies or product formats used in skin care to the scalp. This shift towards scalp care has led to an increase in studies on the scalp, although they remain scarce. It could be argued that the presence of hair on the scalp poses greater challenges for a reliable assessment of scalp properties, as opposed to facial skin. A recent study of the soothing properties of a serum containing Adenosine, Magnesium Sulfate, Vitamin C Glucoside and pre/probiotic fractions, was performed on the scalp. While scalp discomfort and oxidate stress were reduced, no barrier function improvement was observed and skin hydration increase was only evidenced immediately after product application (16).


Because topical solutions targeting scalp itching are limited on the market, the goal was to develop a leave-on scalp serum with desirable tolerability and to address symptoms of a sensitive scalp. In the present article, it is disclosed how a formula intended for scalp use (Cica-Calm Dermo-Soothing Gel, Lazartigue, France) was designed to alleviate sensitive skin, from ingredient selection to clinical efficacy endpoints.

MATERIALS AND METHODS

Plant extracts and formula chassis description 
Two extracts were selected according to their relevancy to reactive skin.

  • Centella asiatica water/glycerin extract: The extract has a history of use in tropical regions and its benefits are attributed to pentacyclic triterpenes such as Asiatic acid, asiaticoside and madecassoside (17). In the context of skin reported properties are anti-inflammatory (18)(19),anti-oxidation(20)wound healing(21). The extract was present at a 2% level in the formula.
  • Rhododendron ferrugineum water/glycerin extract: commonly found in European mountain landscapes, its active fraction is mostly constituted of flavonoids (taxifolin, quercetin, and (+)-catechin), flavanones, orcinol derivatives, phloro-acetophenone, phenolic acids, and pentacyclic triterpene(22). Reported benefits for the skin relate to preventing the carbonylation of skin proteins (23), which can be translated into visible benefits such as facial redness improvement (24). The extract was present at a 1% level in the formula.


Lastly, the formula chassis included glycols and glycerin, to address the skin hydration and skin barrier component (25). The formula type chosen was a leave-on gel serum, with a non-greasy texture, thus it could be applied any time of the day without weighing down the hair. To allow a seamless application directly on the scalp, the selected packaging was a cannula tube for this formula. The full ingredient list is disclosed in table 1.

Table 1. Ingredients list of the scalp serum.

Study panel

22 female volunteers aged 26–72 years old (mean age = 51.0, SD = 5.7) were recruited from Lisbon area in Portugal for this open study. All procedures involved in the study were explained in detail and written informed consent was obtained from all volunteers. Enrolment was definite when volunteers met all inclusion and exclusion criteria. Main inclusion criteria notably included: self-reported sensitive scalp skin, experiencing regular scalp skin discomfort, scalp redness and irritations. Following 15 min acclimatisation under controlled temperature and humidity (21 °C ± 2 °C, relative humidity 55% ± 10%), volunteers went through a set of measurements at baseline, immediately, 30 min, 6 hours, 24 hours after a single product application. Another set of measurements was performed 21 days later, following repeated use of the product where volunteers applied the scalp serum at least three times a week. Volunteers were prohibited from using moisturizing products or serum on their scalp, while maintaining their usual hygiene habits. The study was conducted under Good Clinical Practice (GCP) and in conformance with the most recent recommendations of the World Medical Association (Declaration of Helsinki 1964, amended in Fortaleza, Brazil, 2013).


Measurements

Biophysical parameters such as superficial levels of hydration were collected using capacitance measurements from the Corneometer CM825 (CK Electronic GmbH, Cologne, Germany), while transepidermal water loss (TEWL) was collected with the Tewameter® TM Nano (CK Electronic GmbH, Cologne, Germany) as a skin barrier indicator. This miniaturised version of the Tewameter® , with a diameter of only 2 mm, is particularly suited to measure testing sites covered with hair, such as the scalp. For these two measurements, a control site free of product application and adjacent to the scalp was used for comparison versus the treated area. An initial statistical comparison between the control site and the site to be treated was performed to ensure there were no significant differences and thus guarantee consistency between these two sites. Skin itching was assessed by the volunteers using a Visual Analogical Scale ranging from 0 to 10. Skin redness was scored by a dermatologist using a 9-point severity scale. Illustrative images of the scalp were captured by the mean of a Trichoscan HD® (DermoScan, Regensburg, Germany). Product tolerance and soothing properties were assessed by the dermatologist (physical signs, e.g., erythema, desquamation) and the subject (functional signs, e.g., itching sensation, burning). Lastly, volunteers answered a self-assessment questionnaire with statements about the product efficacy and the following options to answer: Totally agree, agree; disagree; totally disagree. Timings of measurements are outlined on figure 1.

Figure 1. Timings of the measurements.

Statistics

For all the continuous variables evaluated, a distribution confirmation was performed using Kolmogorov-Smirnov and Shapiro-Wilk normality tests. Since departure for normality was observed on continuous variables, baseline comparisons and comparisons versus the control site were performed with the Wilcoxon Ranks Signs Test for both continuous and ordinal variables.

RESULTS AND DISCUSSION

Clinical efficacy

With regards to clinical efficacy, Figure 2 depicts mean values of skin hydration, and associated percentage improvements versus the control area, following a single application of the serum. Skin capacitance was significantly increased in the treated area versus control by 72.1% ± 47.8 (mean ± SD) after 30 min, by 55.0% ± 40.7 (mean ± SD) after 6 hours and by 30.7% ± 30.7 (mean ± SD) after 24 hours.

Figure 2. Skin hydration variation 30 min, 6 hours and 24 hours after a single application of the serum. Bar Plots describe mean ± SD. Asterisks signal a significant difference versus control as follows: * P < .05 (Wilcoxon Ranks Signs Test).

When splitting the data according to the scalp type, higher immediate improvements were observed 30 min after application on oily and dry scalps, compared to normal scalps. Higher improvements were sustained at 6 hours in particular for dry scalps. After 24 hours, the best improvements were still observed on dry scalps, followed by oily scalps (Figure 3).

Figure 3. Skin hydration percentage variation according to skin type

Figure 4 outlines mean values of trans-epidermal water loss, and associated percentage improvements versus the control area, following a single application of the serum. A significant decrease of transepidermal loss was observed in the treated area versus control, of -14.4% ± 16.6 (mean ± SD) after 30 min and -7.1% ± 14.9 (mean ± SD) after 6 hours. The decrease was not sustained up to 24 hours.

Figure 4. Skin transepidermal water loss variation 30 min, 6 hours and 24 hours after a single application of the serum. Bar Plots describe mean ± SD. Asterisks signal a significant difference versus control as follows: * P < .05 (Wilcoxon Ranks Signs Test).

Mean itching intensities are shown in Figure 5, following a single application (imm. and 6 hours) and repeated applications over 21 days. A significant and incremental decrease was recorded over time, by -22.3% ± 77.1 (mean ± SD) immediately, by -50.7% ± 55.1 (mean ± SD) after 6 hours and by -58.2% ± 51.1 (mean ± SD) after 21 days.

Figure 5. Skin itching variation following a single application (imm. and after 6 hours) and repeated application (after 21 days) of the serum. Bar Plots describe mean ± SD. Asterisks signal a significant difference versus baseline as follows: * P < 0.05 (Wilcoxon Ranks Signs Test).

Lastly, Figure 6 shows the skin redness score following a single application (imm. and 6 hours) and repeated applications over 21 days. No improvement was observed immediately. However, significant decreases of -11.4% ± 20.2 (mean ± SD) and -46.5% ± 44.8(mean ± SD) were seen 6 hours following a single application and 21 days after repeated use, respectively. An example of redness decrease over time from a volunteer can be seen in figure 7.

Figure 6. Skin redness variation following a single application (imm. and after 6 hours) and repeated application (after 21 days) of the serum. Bar Plots describe mean ± SD. Asterisks signal a significant difference versus baseline as follows: * P < 0.05 (Wilcoxon Ranks Signs Test).

Figure 7. Scalp images captured by Trichoscan

Subjective efficacy

Following repeated use of the scalp serum over 21 days, volunteers provided positive feedback concerning the improvement of sensitive scalp symptoms (Figure 8), confirming that the benefits were perceived by most of them.

Figure 8. Volunteers' feedback on the scalp serum following repeated applications over 21 days of use

DISCUSSION

Using instrumental measurements such as skin capacitance and transepidermal water loss, Visual Analogical Scale scoring and dermatological scoring, the study aimed at demonstrating the hydrating, skin barrier reinforcing, soothing and redness mitigating benefits of a scalp serum.

Skin barrier and skin hydration were improved as early as 30 min following a single application, with a lasting effect up to 6 hours and 24 hours, respectively. These were relevant clinical endpoints to integrate into this study, since they are considered to be worse on scalp than facial skin (26). More obvious clinical manifestations of sensitive scalp, itching and redness were alleviated both after a single application and repeated use of the serum. It can be speculated that the immediate enhancement of skin hydration and skin barrier imparted by the formulation, combined with the anti-inflammatory and antioxidant properties of the extract, enabled to achieve greater and incremental improvement with repeated application over time. Furthermore, reducing pruritic feelings is crucial for a healthy skin barrier, as it can lead to scratch, whose detrimental effects on TEWL are discussed in the literature (27).

This study showcases how instrumentation and methods, originally suited for facial or body skin, can be transposed for scalp assessment, pending methodologic or instrumentation adjustments, like the Tewameter® TM Nano. Their use should be democratized, beyond the assessment of sensitive scalps. Similarly, a placebo-controlled study for an anti-dandruff ingredient successfully used instrumentation on the scalp to demonstrate its efficacy (28).

Going forward, an interesting target would be patients with psoriasis, since itch is correlated to the severity of scalp psoriasis (29). Inclusion of a placebo group would add value to better discriminate the perceived efficacy of the serum by the volunteers. The inclusion of instrumentation measuring pain threshold could provide additional insights to assess the reactivity threshold of the scalp. Indeed, the more the scalp exhibits skin disorders e.g. erythema, scaling, acne lesions, the lower the threshold to elicit discomfort, as measured by neurometer (26). Lastly, addressing sensitive scalp via modulation of the scalp microbiome seems to be a promising strategy. Similarly to dandruff, mitigating Malassezia restricta abundance appears to be correlated with less reactive scalp (12).

CONCLUSION

Sensitive scalp is a prevalent issue among the population that requires targeted solutions. A topical serum including two plant extracts was shown to alleviate the burden of reactive scalp, in the short term after a single application and in the long term with repeated applications. This illustrates how sensitive skin is no longer a topic exclusive to facial care and can be expanded to other body parts using relevant ingredients and testing approaches inspired by skin care.

Conclusion

The future of cosmetics lies in the continued evolution of holistic approaches which represents a transformative shift in the industry, merging scientific advancements, natural ingredients, and wellness principles. By understanding and embracing the interconnectedness of these elements, the cosmetics industry can cultivate products that not only enhance external beauty but also contribute to the overall well-being of individuals and the planet.


The interplay between beauty from within and topical cosmetics is the key for future products. The integration of biotechnology and green chemistry is revolutionizing cosmetic formulations, offering sustainable and biocompatible alternatives.


Developers can implement blockchain to trace the journey of ingredients from source to product. Nevertheless, the efficacy of the natural products should be scientifically proven. Marketers can communicate transparency as a brand value, and parallelly educate consumers by highlighting how specific ingredients contribute to radiant and healthy skin.


By embracing the synergy between these approaches and leveraging scientific advancements, the cosmetics industry can provide consumers with comprehensive beauty solutions that cater to both internal and external dimensions of beauty.

References and notes

About the Author

CYRIL MESSARAA

Cyril Messaraa holds a Master in Cosmetic Science from the ISIPCA and the University of Versailles, France.
C’kin matters - Graduated in chemistry and biology from ISPICA in France, a higher education institute in the field of perfume, cosmetics, and flavouring, Cyril is an innovative and passionate scientific consultant with 10+ years of experience in the cosmetic industry. Throughout his career, he has authored over 25 peer-reviewed articles, columns in cosmetics media and conference presentations.

CYRIL MESSARAA
C’kin Matters, Kallithea, Greece

References and notes

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