Innovative approaches to avoid electric shaving-induced skin irritation

International Journal of Cosmetic Science, 2016, 38 (Suppl. 1), 10 16 doi: 10.1111/ics.12329 Review Article Innovative approaches to avoid electric shaving-induced skin irritation M. Rietzler*, M. Maurer, F. Siebenhaar, S. Angelino*, J. Handt*, R. Burghardt* and H. Smetana* *Procter & Gamble Braun German Innovation Center, Frankfurter Strasse 145, 61476, Kronberg, Germany and Department of Dermatology and Allergy, Allergie-Centrum-Charite, Charite - Universit atsmedizin Berlin, Berlin, Germany Received 14 March 2016, Accepted 22 March 2016 Keywords: electric shaving, hair growth, hair treatment, male grooming, skin comfort, skin physiology/structure Abstract Globally, millions of men regularly remove their facial hair using an electric shaver. Over the course of several decades, the concept of an electric shaver has evolved from a relatively simple handpowered apparatus to a technologically advanced device designed to provide the user with an optimum shaving experience. This requires a careful balance between robust removal of hair and skin comfort. By incorporating advanced scientific measurement and imaging technology into clinical testing, insights are being gained into skin comfort issues associated with hair removal practices. This study describes new research insights that have guided the development of electric shaving technology. These innovative features are designed to maximize hair removal and minimize the impact on skin health, thus enabling new levels of shaving efficacy and comfort to be attained. Resume A l echelle mondiale, des millions d hommes enlevent regulierement leurs poils du visage a l aide d un rasoir electrique. Au cours de plusieurs decennies, le concept d un rasoir electrique a evolue a partir d un appareil alimente a la main relativement simple vers un dispositif technologiquement avance concßu pour fournir a l utilisateur une experience de rasage optimal. Cela exige un equilibre delicat entre l enlevement robuste de cheveux et le confort de la peau. En incorporant la technologie scientifique de pointe de mesure et d imagerie dans les essais cliniques, les observations sont acquises sur les questions du confort de la peau associees a des pratiques d epilation. Le present document decrit de nouvelles perspectives de recherche qui ont guide le developpement de la technologie de rasage electrique. Ces fonctionnalites innovantes sont concßues pour maximiser l epilation et de minimiser l impact sur la sante de la peau, permettant ainsi a de nouveaux niveaux d efficacite du rasage et du confort a atteindre. Correspondence: Miriam Rietzler, P&G Braun & Appliances - German Innovation Center, Frankfurter Strasse 145, 61476 Kronberg, Germany. Tel.: +49 6173 300; fax: +49 6173 80 1617; e-mail: rietzler. m@pg.com Previous publications: Symposium presentation at the 23rd World Congress of Dermatology in Vancouver, Canada, June 2015. Introduction First patented in 1928, the electric shaver quickly became popular because it offered convenience, allowing the user to shave without using any shaving cream. The first electric shavers had a comb-like metal layer that shielded the user s skin from the blades beneath it. It was not until the 1950s that Max Braun developed a key design innovation a thin, perforated metal foil that covered the cutting blades. When the user placed this surface against the face, facial hairs went through the holes and were trimmed by the blades. This foil was thinner than the metal combs on other devices and therefore provided a closer shave than its predecessors, while still protecting the skin from the blades beneath. Over the course of several decades, the electric-powered shaver has continued to evolve with innovation driven by an in-depth understanding of men s shaving needs, the science behind shaving and the impact of shaving on skin. This has allowed scientists to develop improved technologies that maximize the closeness of the shave with little or no compromise to skin comfort. Today, modern electric shavers are the product of extensive research and technologically advanced manufacturing procedures to provide the user with an optimum shaving experience. How electric shavers work The electric shaver consists of a set of oscillating or rotating blades, which are held behind a perforated metal screen or foil. The foil prevents the blades from coming into direct contact with the skin and acts much like the second blade in a pair of scissors. When the shaver is pressed against the skin, the hairs are forced up into the holes in the foil and held in place before being cut by the moving blades. There are two main types of electric shavers, foil and rotary. Rotary shavers use a cutting system based upon circular blades that rotate under a slotted head or heads. They may contain one to five rotating blades and heads. The shaver is moved across the face in slow, rotating movements (Fig. 1A). Foil shavers use an electric motor to drive the oscillation of the cutting blades. Modern foil shavers are controlled by a pre-programmed electronic circuit which adjusts the power depending on the thickness of the beard. Up to five rows of blades are positioned under a 50 60-lm-thin, curved metal foil. Long and straight movements of the shaver over 10 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie

the face against the hairs growth direction render optimal results (Fig. 1B). The elements of a good shave Electric shaving performance can be defined as a combination of the following attributes: (A) Closeness related to smoothness and shave longevity. Thoroughness the absence of remaining hairs after the shave. Efficiency the amount of hair cut per stroke and speed to the end result. Skin comfort the absence of shaving irritation and/or negative sensory response during and after the shave. Precision the ability to shave precisely around edges such as the sideburns. According to male users of electric shavers, an ideal shave is one which maintains a favourable balance between all of these attributes. The goal is to achieve a close, thorough and comfortable shave with minimal impact on skin and no shave-induced skin irritation. Shaving and skin comfort Shaving-related skin irritation is one of the most frequently noted male cosmetic complaints in Europe and the United States [1]. In one study, 41% of men with self-reported sensitive skin reported skin reactions after shaving; the most common of which were redness, burning and stinging [2]. These reports did not distinguish between manual shaving and electric shaving. In addition 90% of dermatologists agree that the selection of shaving products was important for men with sensitive skin [5]. Skin irritation in electric shaving is largely the result of the interaction of the skin with the shaver s cutter, which happens when the skin is pressed into the small apertures of the shaving foil. The interaction with the shaver s cutter can lead to mild abrasion of the outer skin layers [3]. This in turn can stimulate nerve endings and activate cell signalling pathways that trigger the release of cytokines. These responses are believed to give rise to the typical signs of shaving-induced irritation, including the perception of burning and itching on the skin and an increased blood flow, making skin appear more erythematous (Fig. 2). Signs and symptoms of electric shaving-induced skin irritation Figure 1 The two main types of electric shavers: (A) rotary and foil shaver. Both systems use a foil that stays in contact with the skin while a cutting blade moves beneath it. The main difference between the two systems is the direction in which the cutting blade moves. In the rotary system, the blade moves in circles underneath the foil. In the foil system, the blade moves from one side to the other in a linear movement. Research in the area of male hair removal has identified several key issues that men experience when removing hair with an electric shaver. These manifest as either visible signs of electric shaving-induced skin irritation or subjective sensations as shown in Table I. The most commonly reported signs and symptoms of electric shaving-induced skin irritation include skin dryness, roughness and erythema, papule formation and microlesions, all of which can be associated with a sensation of skin tightness, itch, burning, and warmth of the skin (Table I). The prevalence and relevance of electric shaving-induced skin irritation differs somewhat with geography, with men from Japan and the United Kingdom most frequently reporting razor burn as a key indicator of irritation (41% and 30%, respectively). In the United States, ingrown hairs were cited as the most commonly occurring type of shaving issue, whereas in Germany skin dryness/tightness after the shave was most commonly reported (Table II). Measuring shaving comfort Traditionally, studies of the impact of shaving on skin have relied upon self-assessment, conducted immediately after the shave. 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie 11

(A) Before electric shaving Table II Proportion of men self-reporting shaving-induced irritation Proportion of men self-reporting shaving-induced irritation by country (%) Type of irritation United States Japan Germany United Kingdom After electric shaving Dryness/tightness 15 34 22 22 after shaving Razor burn 18 41 10 30 Razor bumps 17 9 16 8 Nicks/cuts from 18 23 11 21 shaving Ingrown hairs 27 9 11 15 Redness 12 14 21 20 Dry skin 18 32 17 23 Flaky skin 8 9 6 9 Rough spots 4 17 1 4 has helped to demonstrate that electric shaving, of the neck region in particular, can increase blood perfusion at the treated area (Fig. 3). Methods such as this allow quantification of the shavinginduced skin responses and correlation with subjective attributes of skin comfort and irritation. In this way, insights are being gained into unwanted skin responses to electric shaving, an important prerequisite for the development of improved strategies for avoiding shaving-induced skin irritation. Strategies to avoid skin irritation associated with electric shaving Figure 2 The neck area of an individual shown (A) before and after electric shaving. Redness, one of the visible signs of electric shave-induced irritation, can be observed on the neck area in image. Table I The visible signs and subjective sensations associated with shavinginduced irritation Dryness and scaly or flaky skin Roughness Redness Papules Microlesions Skin tightness Dryness Itching Burning Increased warmth during and after shaving Many men adopt compensatory behaviours to mitigate the discomfort associated with shaving. Differences are observed in all aspects of shaving behaviour, including the regimen deployed prior to and after the shave as well as the number, direction, speed and force of shaving strokes used. Some men may avoid shaving altogether. In one survey, over 50% of men with sensitive skin stated they chose to forego their preferred shaving schedule as a result of the discomfort associated with prolonged irritation of sensitive areas [4]. Guinot et al. [2] found that 60% of men with self-assessed sensitive skin reported skin reactions after shaving including redness, burning and stinging. With an increasing number of men reporting that they have sensitive facial skin (66% of respondents in a global survey of 3326 men) [4], and dermatologists reporting an increase in the number of men presenting with sensitive skin [6], there is a clear need for innovations in product design that minimize electric shavinginduced skin irritation. Shaver performance is evaluated through in-depth questionnaires, designed to explore the many different attributes of shaving including comfort, efficiency, closeness and thoroughness. Blinded expert grading can provide a robust and objective assessment of the visible signs of electric shaving-induced skin irritation. More recently, advanced scientific measurement and imaging technologies are being incorporated into clinical testing. For example, blood perfusion measured using laser speckle contrast technique is used to assess electric shaving-induced changes in skin blood flow. This Active cooling during shaving Modern electric shavers comprise multiple highly advanced technological features that act to manage the skin and the hair during the shaving process. To limit the increase in blood flow and to avoid burning and increased warmth during and after shaving, typical signs of shave-induced skin irritation, some of the most technologically advanced electric shavers comprise an integrated cooling system designed to actively cool the skin during the shaving process (Fig. 4). 12 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie

(A) Blood perfusion imaging (A) Thermoelectric cooling technology Marker Analysed area Heat sink Thermoelectric cooler Aluminium bar Before electric shaving After electric shaving Laser speckle contrast measurement recording. The vertical blue lines indicate when the expert grading assessment was made. Blood perfusion (perfusion units) (seconds) Figure 3 Laser speckle contrast imaging of blood flow in the cheek and neck area, before and after electric shaving. (A) Markers were placed onto the skin of the cheek and neck to ensure the same areas were analysed before and after shaving. Blood flow is colour-coded, with areas of low perfusion shown as blue and areas of high perfusion shown as red. Blood perfusion tracing in a subject over a time period of 20 min (5 min pre-shave, 15 min post-shave). After shaving, increased blood perfusion in the neck area was observed (red line) but not in the cheek area (black line). In some modern electric shavers, an actively cooled aluminum bar, integrated into the shaver head, is located between the shaving foils next to the central trimmer. During the first seconds of operation, the temperature of this element is reduced by 20 C relative to the ambient temperature and this temperature is maintained throughout the shaving process. When the so cooled aluminum bar makes contact with the skin during shaving, it actively transports heat away from and cools the skin surface as measured by thermal imaging (Fig. 5). A randomized, split-face clinical study was conducted at the Department of Dermatology and Allergy, Charite Universit atsmedizin Berlin to assess skin responses induced by electric shaving with and without active cooling (n = 96 males with selfassessed sensitive skin; 18 38 years of age). Subjects were randomized for shaving site allocation and sequence. They then shaved one side of their face for 90 s using the shaver with cooling and the contralateral side of the face without cooling. Signs and symptoms of shaving-induced skin irritation Active cooling of the skin surface Thermoelectric cooler Active cooling of the skin surface Heat transfer from the skin surface Aluminium bar Figure 4 An advanced electric shaver with thermoelectric cooling technology. (A) The primary component is a thermoelectric cooler which is on one side connected to an aluminum bar located between the shaving foils and next to the center trimmer. On the other side this thermoelectric cooler is connected to a heat sink integrated into the shaver body. When the so cooled aluminium bar contacts the skin surface during shaving, heat is actively transported away from the skin surface into the heat sink causing the skin surface to cool down. were assessed 10 min after each shave by a blinded dermatologist with the help of visual analogue scales. Subjects scored their perceived symptoms of shaving-induced irritation using four-point Likert scales. Active cooling of the skin during shaving resulted in a significant reduction in the typical signs of electric shaving-induced skin irritation, specifically skin discomfort, skin agitation, skin irritation overall, tension and burning as determined by subject self-assessment (Fig. 6A) [6]. Further, electric shaving-induced skin irritation as determined by blinded dermatologist assessment was significantly reduced in subjects who had active cooling during the shave when compared with those who did not (Fig. 6B) [6]. This is consistent with clinical findings demonstrating that orofacial somatosensory perception in healthy adults can be altered by thermal cooling. Localized cooling of the posterior cheek, using a 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie 13

(A) Electric shaver without active cooling Electric shaver with active cooling (A) Subject self-assessment scores *** *** ** * * Figure 5 Thermal imaging of the skin surface after shaving an area of the cheek using an electric shaver (A) without thermoelectric cooling technology and with thermoelectric cooling technology. Areas with the lowest skin surface temperature are shown as blue, and areas with the highest skin surface temperature are shown as red. metal contact plate (30 9 30 mm) connected to an external Peltier device, was found to reduce pain sensitivity to pinprick stimuli and increase tolerance to applied pressure [7]. Speed and efficiency of the shave Keeping the shaving process as short and efficient as possible may reduce skin irritation by minimizing the time the skin is in contact with the shaver. Facial hairs, due to their complex and often variable growth patterns, can be difficult to capture and cut [8]. When hairs are missed during shaving, men may repeatedly go over the same area of skin. Repeat shaving over a given facial area has been shown to lead to increased dry shaving irritation [9]. Thus, the use of electrical shavers that capture more hairs in one stroke is postulated to prevent shaving-induced irritation. In a recent survey conducted during the 23rd World Congress of Dermatology in 2015, the majority of dermatologists agreed with the statement that electrical shavers that capture more hairs in one stroke are also more gentle to the skin (Fig. 7). To this end, innovations in electric shaving aim to (i) reduce contact between the electric shaver and the skin, (ii) improve capture of hairs with minimal impact to the skin and (iii) optimize cutting of hairs close to the skin surface without causing shavinginduced skin irritation. Dermatologist assessment scores * Contact between the electric shaver and the skin To maximize the number of hairs captured in one stroke, there must be a good contact between the shaver and the skin surface. Following the curves and contours of the face can be a challenge for any shaving system. Many modern shavers are designed with cutting elements that can move independently of one another to accommodate skin surface irregularities. Some, for example, feature a pivoting head that can adapt to facial contours such as those found on the jawline and chin. Capture of hairs Before they can be cut, hairs must be captured by the foil and presented to the blades for cutting, and, at the same time, the Figure 6 The effect of active cooling on shaving-induced skin reactions as determined by (A) subject self-assessment using four-point Likert scales and blinded dermatologist assessment with the help of visual analogue scales. Error bars indicate standard deviation; statistical significance is denoted by: ***P < 0.005, **P < 0.01, *P < 0.05 14 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie

(A) Skin bulging without guard Hair Uneven skin bulge, no localized skin stretching Figure 7 Survey results among international dermatologists (n = 2266) in response to the statement: electrical shavers that capture more hairs in one stroke are also more gentle to the skin. Using a five-point scale respondents were asked to indicate how much they agreed or disagreed with the statement. The research was conducted by Ipsos Reid LP during the 23rd World Congress of Dermatology in Vancouver, Canada, from June 9 12, 2015. Dermatologists voluntarily chose to self-complete the survey without any incentives. Skin bulging with guard Hairs Skin bulge immediately behind the guard, causing localized skin stretching (A) Very thin trimmer for low lying hairs Figure 9 Ultra-high speed filming images of skin and hair (A) without stretch from a guard and with stretch from a guard showing the impact of the guard in applying localized stretch to the skin surface. Stretching the skin ahead of the cutting blades results in a smoother skin surface to be shaved and presents hairs in a more favourable manner for cutting. Very thin trimmer: to lift and cut flat-lying hairs in the neck and chin area Trimmer designed to direct, align and cut multi-directional, longer hairs Floating cutting elements: to follow facial contours Skin guard: to stretch skin ahead of the cutters and present hairs for cutting Pivoting head: to follow the contours of the face and neck Additional trimmer: to capture hairs growing in different directions Foil: ergonomically sized holes for capturing hairs not skin Ultrasonic technology: microvibrations may help to capture hair Figure 10 Some key components of a modern foil shaver. Figure 8 Examples of some trimmers available in modern electric shavers optimized to capture hairs. (A) shows a very thin trimmer designed to go under low lying hairs and shows a trimmer designed to capture and cut longer hairs that grow in different directions. surrounding skin must be managed to prevent irritation. Modern foils have been ergonomically designed to effectively capture hair without compromising the surrounding skin substrate. This requires careful optimization of the number, size, shape and spacing of the apertures in the foil. For example, the apertures must be of sufficient size to allow hairs to enter the foil without engaging the surrounding skin, which would result in skin irritation. Practical considerations such as strength, rigidity and flexibility of the foil substrate must also be considered so as to not compromise the foil structure. One method for arranging the apertures within the foil utilizes a constrained Voronoi tessellation, a principle defined by the mathematician Voronoi [10]. It uses a non-repetitive 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie 15

pattern to optimize the stability of very thin structures such as those observed in nature, for example, in the wings of a dragonfly. In this way, a highly robust foil can be designed to be <60 lm thick despite containing more than 1000 holes. Product comparison studies demonstrated that the foil designs based on this principle significantly improved the closeness and efficiency (hair removed per stroke) of the resulting shave without increasing shaving-induced skin irritation when compared with previous embodiments not utilizing this principle (unpublished data on file by authors). Despite advancements in foil design, longer hairs and low lying hairs that grow in multiple directions can still present a challenge when shaving. Longer hairs may bend over and lie flat against the skin instead of being pushed through the openings of the foil. Low lying hairs, such as those found on the neck [8], may also evade capture by the foil. To address this, specialized trimmers have been incorporated into some advanced shaver systems in direct association with the apertured foil (Fig. 8). Other innovations aimed at increasing the efficiency of hair capture include vibration of the shaver foil or cutting elements at an ultrasonic rate, which is claimed to increase the uptake of hairs [11]. However, the exact mechanism is not fully understood. Cutting of hairs The process of a blade cutting through hair can lead to an unpleasant pull and tug sensation [8]. The more efficient and effective the cutting process, the less likely adverse sensory shave-induced responses occur. Stretching the skin ahead of the cutting blades results in a smoother skin surface to be shaved and presents hairs in a more favourable manner for cutting [8, 12]. Figure 9 shows ultra-high-speed filming images of skin and hair that illustrate the change in local topography achieved by stretching the skin with a guard. Optimizing the geometry of blade edges has also been found to improve cutting efficiency and to reduce shaving-induced skin irritation [8]. The optimum shaving experience In summary, for the optimum electric shaving experience, hair must be efficiently captured and cut with minimal impact to the skin. Low lying hairs, longer hairs and hairs that grow in different directions present a significant challenge as men may have to repeatedly shave over the same area of skin, which can lead to skin irritation. The technical solutions designed to improve skin comfort can be divided into those that improve hair cutting efficiency and thoroughness, thereby minimizing the opportunity for electric shaving-induced skin irritation to occur and those that target the skin directly, for example, by delivering active cooling during the shave to mitigate irritation. When these multiple, highly advanced technological features are combined in modern electric shavers (Fig. 10), they may act synergistically to improve shaving efficiency, closeness, removal of difficult hairs and skin comfort [13]. The understanding of electric shaving-induced skin irritation has markedly evolved in recent years leading to the development of technologically advanced products that more effectively address the hair removal and skin care needs of men. Many questions, however, remain to be answered: what are the determinants and drivers of shaving-induced skin irritation? Do endogenous factors such as age or environmental factors modulate the susceptibility to shavinginduced irritation? Future studies will need to address these issues. Acknowledgements All studies were funded by The Procter and Gamble Company. Editorial writing assistance, supported financially by The Procter and Gamble Company, was provided by Dr Gill McFeat of McFeat Science Ltd. The author(s) were fully responsible for all content and editorial decisions, were involved at all stages of manuscript development and have approved the final version. Dr Rietzler, Dr Angelino, Dr Handt, Dr Burghardt and Dr Smetana are employees of Procter & Gamble. M. Maurer and F. Siebenhaar received honoraria for advise and lectures and institutional funds from Procter and Gamble. References 1. Elsner, P. Overview and trends in make grooming. Br. J. Dermatol. 166, 2 5 (2012). 2. Guinot, C., Malvy, D., Mauger, E. et al. Selfreported skin sensitivity in a general adult population in France: data of the SU.VI.- MAX cohort. J. Eur. Acad. Dermatol. Venereol. 20, 380 390 (2006). 3. Bhaktaviziam, C., Mescon, H. and Matoltsy, A.G. Shaving I. Study of skin and shavings. Arch. Dermatol. 88, 874 879 (1963). 4. Procter & Gamble. Male Skin: An Increasingly Sensitive Subject. Available at: http:// orders.pgdermatology.com/theme/web/images/home/white_paper_male_skin_an_increasingly_sensitive_subject.pdf, accessed 1 October 2015. 5. Vanoosthuyze, K., Zupkosky, P.J. and Buckley, K. Survey of practicing dermatologists on the prevalence of sensitive skin in men. Int. J. Cosmet. Sci. 35, 388 393 (2013). 6. Siebenhaar, F., Smetana, H., Burghardt, R., Angelino, S., Rietzler, M. and Maurer, M. Simultaneous active cooling reduces shaving-induced skin responses. Poster 00527, presented at: The 23rd World Congress of Dermatology, June 2015; Vancouver, BC. 7. Oono, Y., Wang, K., Atis, E.S. and Arendt- Nielsen, L. Thermal application modulates orofacial somatosensory perception in healthy men and women. Clin. Neurophysiol. 124, 581 588 (2013). 8. Cowley, C. and Vanoosthuyze, K. Insights into shaving and its impact on skin. Br. J. Dermatol. 166, 6 12 (2012). 9. Elden, H.R. Advances in understanding mechanisms of shaving. Cosmet. Toilet. 100, 51 62 (1985). 10. Voronoi, G.F. Nouvelles applications des parametres continus a la theorie de formes quadratiques. Journal f ur die reine und angewandte Mathematik 134, 198 287 (1908). 11. Balamuth, L. and Karatjas, M. Ultrasonic electric shaver. United States; US3756105 (1973). 12. Hollander, J. and Casselmanm, E.J. Factors involved in satisfactory shaving. JAMA 109, 95 101 (1937). 13. Warentest, S. Electric Shavers. Available at: https://www.test.de/elektrorasierer-auchguenstige-scheren-gut-4633728-0/, accessed 6 October 2015. 16 2016 Society of Cosmetic Scientists and the Societe Francßaise de Cosmetologie