ArticlePDF Available

The Scalp Has a Lower Stratum Corneum Function with a Lower Sensory Input than Other Areas of the Skin Evaluated by the Electrical Current Perception Threshold

Authors:

Abstract and Figures

Many people feel frequent prickling or itching sensations on their scalp. The scalp is an atypical area of the skin since it is normally covered with thick hair and has many sebaceous glands and sweat glands. The scalp often has skin problems that can affect its sensitivity and functions. However, not much is known about stratum corneum function and the neural sensitivity of the scalp. Here we evaluated stratum corneum function and the neural sensitivity of the scalp of 47 normal male individuals in various skin conditions and compared the results to that to the forehead. The neural sensitivity was evaluated by measuring the electrical current perception threshold (CPT). The cutaneous barrier function and stratum corneum moisture-retention ability (MRA) of the scalp were significantly lower than on the forehead, even if there were some scalp problems. Depending on the increase in severity of scalp skin problems, both these skin functional properties and the CPT decreased significantly. However, regardless of its lower functional properties, scalp skin was not significantly lower than that of the forehead. Although the scalp has a low stratum corneum function compared with the forehead and has easily induced skin problems, the scalp skin has less sensitive sensory nerves, resulting in experiencing a worsening of scalp symptoms more easily.
Content may be subject to copyright.
Cosmetics 2015, 2, 384-393; doi:10.3390/cosmetics2040384
cosmetics
ISSN 2079-9284
www.mdpi.com/journal/cosmetics
Article
The Scalp Has a Lower Stratum Corneum Function with
a Lower Sensory Input than Other Areas of the Skin Evaluated
by the Electrical Current Perception Threshold
Yutaka Takagi *, Hiroko Takatoku, Hiroyuki Terazaki, Tadashi Nakamura, Koichi Ishida and
Takashi Kitahara
Kao Corporation, R&D, 2-1-3 Bunka, Sumida-ku, Tokyo 131-8501, Japan;
E-Mails: takatoku.hiroko@kao.co.jp (H.Ta.); terasaki.hiroyuki@kao.co.jp (H.T.);
nakamura.tadashi@kao.co.jp (T.N.); ishida.koichi@kao.co.jp (K.I.); kitahara.takashi@kao.co.jp (T.K.)
* Author to whom correspondence should be addressed; E-Mail: takagi.yutaka@kao.co.jp;
Tel.: +81-3-5630-9792; Fax: +81-3-5630-9330.
Academic Editor: Enzo Berardesca
Received: 30 September 2015 / Accepted: 17 November 2015 / Published: 20 November 2015
Abstract: Many people feel frequent prickling or itching sensations on their scalp.
The scalp is an atypical area of the skin since it is normally covered with thick hair and has
many sebaceous glands and sweat glands. The scalp often has skin problems that can affect
its sensitivity and functions. However, not much is known about stratum corneum function
and the neural sensitivity of the scalp. Here we evaluated stratum corneum function and the
neural sensitivity of the scalp of 47 normal male individuals in various skin conditions and
compared the results to that to the forehead. The neural sensitivity was evaluated by
measuring the electrical current perception threshold (CPT). The cutaneous barrier function
and stratum corneum moisture-retention ability (MRA) of the scalp were significantly
lower than on the forehead, even if there were some scalp problems. Depending on the
increase in severity of scalp skin problems, both these skin functional properties and the
CPT decreased significantly. However, regardless of its lower functional properties, scalp
skin was not significantly lower than that of the forehead. Although the scalp has a low
stratum corneum function compared with the forehead and has easily induced skin
problems, the scalp skin has less sensitive sensory nerves, resulting in experiencing a
worsening of scalp symptoms more easily.
OPEN ACCESS
Cosmetics 2015, 2 385
Keywords: scalp skin; stratum corneum; current perception threshold; forehead
1. Introduction
The scalp is a peculiar type of skin that is normally covered with thick hair and has many sebaceous
glands and sweat glands. Those special circumstances may cause a prickling or itching feeling on the
scalp, which is felt very often by some subjects. We have found that about one-third of people worry
about these unpleasant feelings in Japan (data not shown). Furthermore, the scalp can have many
additional problems, such as dandruff, odor, and so on. To take care of the scalp and hair, many hair
care products, such as shampoos, hair conditioners, hair styling products, and drugs, are used almost
daily. There are many reports about dandruff [1–4]. Bin Saif reviewed scalp pruritus, the nerves on
hair follicle and hair, and mediators and receptors involved in the itchy sensation [5]. However, there
are few reports about the stratum corneum functions [4–7] or the sensitivity of the scalp [8–12]
compared with skin at other body regions. Furthermore, the evaluations of actual nerve reactions
compared with other body regions are very few. In this study, we analyzed the skin’s functional
properties and the neural sensitivity of the scalp. The electrical current perception threshold (CPT) of
sensory nerves measured with a Neurometer
®
has been used to demonstrate abnormalities in
neuropathic conditions [13–15] and also to evaluate sensitive skin [16]. The sensitivity of the scalp to
electric stimulation using a Neurometer
®
was compared to the forehead of each subject. Furthermore,
we analyzed the relationship between skin properties and neural sensitivity and various scalp
conditions, such as erythema, scaling, papules, and so on. From these analyses we found that the scalp
has a low stratum corneum function compared with the forehead and has easily induced skin problems;
however, the scalp skin has fewer sensitive sensory nerves, resulting in experiencing a worsening of
scalp symptoms more easily.
2. Experimental Section
2.1. Study Design
The present study adhered to the tenets of the Declaration of Helsinki. All clinical studies were
reviewed and approved by the Review Board of the Kao Corporation (Tokyo, Japan) and formal
informed consent was obtained from each subject before the study.
2.2. Participants
Healthy male subjects were recruited randomly and 47 male volunteers participated in this study.
Subjects with alopecia areata, severe scalp eczema, and/or severe dandruff were excluded.
2.3. Test Procedure
Each subject washed his head and face on the eve of the evaluation day. Following this washing,
topical application of skin care products on the analyzed areas was prohibited until after the skin
Cosmetics 2015, 2 386
evaluation. Both sides of the head (a 5 mm × 5 mm area 5 to 7 cm above the ear) were used for the
evaluation. The hairs of the evaluated areas were removed by scissors immediately before the
evaluation. Sebum levels on the forehead and the scalp were analyzed with a Sebusheet
®
ASS-001
(Asahi Techno Lab. Ltd., Kanagawa, Japan) according to seven grades (0, 25, 50, 75, 100, 150, and
200 μg/cm
2
). A TPX-90 Handy PH meter (Tokyo Glass Kikai Ltd., Tokyo, Japan) was used with a flat
glass electrode according to EEMCO guidance [17]. The average value of three measurements was used
for analysis. The CPT was measured with an electric current sine wave stimulator of sensory nerves
(Neurometer
®
CPT/C, Neurotron Inc., Baltimore, MD, USA). Three sine wave stimulations (at 2000,
250, and 5 Hz) produced by the Neurometer
®
provided selective simulations for three subsets of nerve
fibers [15]. Following these measurements, the head and forehead of each subject was washed with a
cleanser and dried by a specialist. After acclimation at 20 ± 2 °C, 40% ± 5% humidity for 20 min,
transepidermal water loss (TEWL) and stratum corneum moisture-retention ability (MRA) were
measured with a Tewameter TM210
®
(Courage + Khazaka electronic GmbH, Cologne, Germany) and
a Corneometer
®
CM825 (Courage + Khazaka electronic GmbH), respectively. Specialists who were
internally trained visually rated the scaling, erythema, papules, eschars, pustules, and nodules on a
scale of 0 to 4 (0 = none, 1 = slight, 2 = mild, 3 = moderate, and 4 = severe) on the evaluated areas of
the scalp.
2.4. Statistical Analysis
Data obtained from both sides of the head were calculated as averages. Differences between the
scalp and the forehead were determined statistically with Student’s paired t-test.
3. Results
3.1. Participants with Skin Symptoms
Forty-seven males, aged 27 to 46 years old (36.1 ± 4.8, mean ± S.D.), were included in this
evaluation. All subjects had hair on the evaluated areas and none of them had severe scalp problems.
Their scalp conditions are summarized in Table 1.
Table 1. Scalp skin symptoms of subjects.
Score Scaling Erythema Papule Eschar Pustule Nodule
0 15 3 28 35 31 43
1 18 26 11 8 12 3
2 11 14 8 4 1 1
3 3 4 0 0 3 0
4 0 0 0 0 0 0
SUM 47 47 47 47 47 47
Cosmetics 2015, 2 387
3.2. Comparison of Measured Data between the Scalp and the Forehead
Prior to washing the scalp and the face, the sebum level of the scalp was more than 50% higher than
that of the forehead (scalp: 89 ± 29 μg/cm
2
, forehead: 59 ± 31 μg/cm
2
, p < 0.01, Figure 1A). However,
the average skin surface pH of the scalp was similar to that of the forehead (scalp: 4.80 ± 0.45,
forehead: 4.80 ± 0.40, Figure 1B).
Following washing with the cleanser, the MRA of the scalp was significantly lower than that of the
forehead (scalp: 34.5 ± 9.4, forehead: 54.3 ± 11.2, p < 0.01, Figure 1C) and the TEWL of the scalp was
significantly higher than that of the forehead (scalp: 6.6 ± 1.6 g/m
2
·hr, forehead: 5.5 ± 1.6 g/m
2
·hr,
p < 0.01, Figure 1D).
Figure 1. Comparison of measured data for sebum level (A), skin surface pH (B), MRA (C),
and TEWL (D) between the scalp and the forehead. Each column indicates the average and
the bars show standard deviation. ** indicates p < 0.01 as a significant difference.
The CPT on the scalp and the forehead was measured with a Neurometer
®
prior to washing with the
cleanser. Although the MRA and TEWL of the scalp indicate that the scalp has a lower stratum
corneum function than the forehead, the scalp had a significantly higher CPT value than the forehead
(Figure 2A–C).
A
Scalp Forehead
3.0
4.5
5.0
5.5
6.0
B
D
g/m
2
·hr
0
2
4
6
8
10
12
C
20
40
60
80
100
a.u.
0
Scalp Forehead
0
μg/cm
2
50
100
pH
Scalp Forehead Scalp Forehead
**
**
**
150
4.0
3.5
Cosmetics 2015, 2 388
Figure 2. Comparison of measured data for CPT for 2000 Hz (A), 250 Hz (B), and 5 Hz (C)
between the scalp and the forehead. Each column indicates the average and the bars show
standard deviation. * indicates p < 0.05 and ** indicates p < 0.01 as a significant difference.
3.3. Comparison of Measured Data between Scalps with Skin Symptoms of Different Severity
and the Forehead
The properties of the stratum corneum and the cutaneous sensitivity might be affected by the skin
symptoms. Thus, we analyzed the relationship between the stratum corneum properties and the
severity of skin symptoms (as shown in Table 1) and found that every skin symptom affected the
stratum corneum properties and the cutaneous sensitivity with the same tendency (data not shown).
Because of the low severity of each type of skin symptom, the subjects were classified into three
groups according to the severity of the scalp skin problem. Group I did not have any kind of skin
symptoms with a severity score of more than 1 (n = 21), Group II had one skin symptom with a
severity score of more than 1 (n = 12), and Group III had more than one skin symptom with a severity score
of more than 1 (n = 14).
Depending on the increase in the severity of scalp skin problems, the sebum level decreased
significantly, but even Group III had more sebum on the scalp than on the forehead (Figure 3A).
The skin surface pH was significantly higher with the increased severity of skin problems (Figure 3B).
The MRA of the scalp of Group I was significantly lower than that of the forehead and was dependent
on the increased severity of skin problems (Figure 3C). The TEWL of the scalp of Group I was
significantly higher than that of the forehead, but it was even higher in Groups II and III (Figure 3D).
Scalp Forehead
20
40
60
80
0
Scalp Forehead
0
50
100
150
200
Scalp Forehead
**
250
20
40
60
80
100
CPT value x10mA
0
*
CPT value x10mA
CPT value x10mA
p=0.09
A
B
C
Cosmetics 2015, 2 389
Figure 3. Comparison of measured data for sebum level (A), skin surface pH (B), MRA (C),
and TEWL (D) between scalps with skin symptoms of different severity and the forehead.
Each column indicates the average and the bars show standard deviation.
* indicates p < 0.05, ** indicates p < 0.01 and *** indicates p < 0.001 as a significant
difference. NS indicates as no significant difference.
The CPT on the scalp of Group I was significantly higher than that of the forehead at each level of
current. Depending on the increased severity of skin problems, these values decreased significantly in
Groups II and III. Only the 2000 Hz current had a higher CPT value on the scalp of Group III than on
the forehead and there was no significant difference in the CPT value for 250 and 5 Hz, even in
Group II (Figure 4A–C).
Figure 4. Cont.
0
2
4
6
8
10
12
20
40
60
80
100
a.u.
0
0
μg/cm
2
50
100
150
**
I
3.0
4.5
5.0
5.5
6.0
Scalp
Forehead
pH
4.0
3.5
II III
I
Forehead
II III
*
I
Scalp
Forehead
II III
I
Forehead
II III
*
***
***
*
NS
***
***
A
B
DC
g/m
2
·hr
0
50
100
150
200
250
20
40
60
80
CPT value x10mA
0
CPT value x10mA
**
I
Scalp
Forehead
II III
*
I
Scalp
Forehead
II III
*** **
*
NS
A
B
Cosmetics 2015, 2 390
Figure 4. Comparison of measured data for CPT for 2000 Hz (A), 250 Hz (B), and 5 Hz (C)
between scalps with different skin symptoms and the forehead. Each column indicates the
average and the bars show standard deviation. * indicates p < 0.05, ** indicates p < 0.01 and
*** indicates p < 0.001 as a significant difference. NS indicates as no significant difference.
4. Discussion
Although scalp skin is less sensitive than other areas of skin, there is a high prevalence of pruritus.
Furthermore, the scalp easily develops other skin problems, not only pruritus but also dandruff, odor,
and itching, because it has many sweat glands and sebaceous glands and is usually covered with thick
hair. However, there are only a few reports about stratum corneum function on the scalp. O’goshi et al.
reported that the scalp has a significantly higher high-frequency conductance and a significantly lower
TEWL than the cheek [7]. However, in our evaluation, the scalp has a significantly lower capacitance
and a significantly higher TEWL compared to the forehead. As the skin surface hydration of the cheek
is significantly lower than that of the forehead [18], it is presumed that both the scalp and the cheek
have a lower water-holding capacity compared to the forehead. The lower conductance of the cheek
might be caused by a low sebum level [18], but our evaluation showed that the scalp has significantly
more sebum compared to the forehead. In our evaluation, TEWL and MRA were measured following
skin washing with cleansers and this treatment might cause the different results between these
two evaluations. Additionally, the scalp conditions and hair affect these values, e.g., all subjects in our
evaluation had thick hair on the side of the head that was evaluated. Stratum corneum functions such
as TEWL and MRA are greatly affected by the existence of water such as sweat and sebum. The
amount of sweat and sebum are changes dependent on the subjects’ condition prior to the evaluation.
Thus, to standardize the condition, the stratum corneum functions were evaluated following washing
with cleanser and habituation in this evaluation.
Despite its low stratum corneum functions, the scalp has a higher CPT value which indicates that
the scalp is more sensorily obtuse compared to the forehead. Mori et al. reported that decreases in skin
surface hydration and increases in TEWL are correlated with the decrease in CPT on the forearm [19].
Also, Tominaga et al. reported that dry skin induced by acetone treatment had increased intraepidermal
nerve fibers in mice [20]. The lower stratum corneum functions such as sensitive skin and atopic
dermatitis can easily cause the skin inflammation and pruritus. Moreover, the thicker epidermis [21]
and greater number of stratum corneum layers [6] of the scalp compared to the forehead may affect the
Scalp
20
40
60
80
0
CPT value x10mA
**
I
Forehead
II III
***
NS
C
Cosmetics 2015, 2 391
sensitivity. However, the scalp skin has less sensitive sensory nerves, even if the stratum corneum
functions are low, showing that the scalp is a very special property. The high humidity which leads to
sweat and sebum, resulting in a great deal of moisture on the stratum corneum, might be one reason
causing these less sensitive sensory nerve. Another evaluation indicated that the scalp is notably
insensitive to innocuous and noxious changes in temperature [10]. Moreover, it was reported that scalp
skin is less sensitive to histamine-induced experimental itching compared to the forearm [12], although
the scalp was more sensitive to a sodium lauryl sulphate challenge than the forearm [9].
The CPT of sensory nerves measured with a Neurometer
®
has been used to demonstrate
abnormalities in neuropathic conditions [13–15]. Five Hz stimulates unmyelinated C fibers, resulting
in a slow pain described as “burning” or “stinging”, 250 Hz stimulates Ad fibers with a feeling of fast
pain and temperature, and 2000 Hz stimulates Ab fibers producing the sensations of touch and a more
mechanical quality.
In our evaluation, normal scalp skin was significantly less sensitive against all three of these
electrical stimuli compared to the forehead; these results agree well with the previous reports described
above. However, with increased skin problems and skin surface conditions, the scalp became more
sensitive, almost at the same level as the forehead in Group III, which has relatively severe scalp
problems, especially for 250 and 5 Hz stimuli.
The scalp has low stratum corneum functions even under conditions that readily induce skin
problems, such as high humidity and rich sebum levels which result in the existence of many microbes
such as Malassezia. However, because of its low neural sensitivity, it might be easy to worsen the skin
problems on the scalp. It is presumed that such severe skin circumstances make the scalp insensitive,
but increase the severity of the skin problems. Saint-Martory et al. reported that 36.2% of French
subjects say they suffer from sensitive scalp skin [22]; however, there are very few reports about
sensitive scalp skin [23,24]. Our study shows that, although the scalp has a low stratum corneum
function compared with to the forehead, the scalp skin has less sensitive sensory nerves. Therefore,
scalp skin might have easily induced skin problems and be more prone to worsening compared to other
regions of skin.
5. Conclusions
The scalp skin has less sensitive sensory nerves, despite its low stratum corneum function compared
to that of the forehead. Thus, the scalp skin can suffer from easily induced skin problems and more
adequate care should be necessary for maintaining healthy scalp skin.
Acknowledgments
This study was supported financially by the Kao Corporation. We thank our colleagues in the
Global R&D, Kao Corporation for their kind help during the study.
Cosmetics 2015, 2 392
Author Contributions
Hiroko Takatoku, Takashi Kitahara, Hiroyuki Terazaki, Tadashi Nakamura and Koichi Ishida
conceived and designed the experiments; Hiroko Takatoku and Hiroyuki Terazaki performed the
experiments; Hiroko Takatoku and Yutaka Takagi analyzed the data; Yutaka Takagi wrote the paper.
Conflicts of Interest
No conflict of interest by disclosing any financial arrangements in this paper. All authors are
employees of Kao Corporation and this study was supported financially by Kao Corporation.
References
1. Hay, R.J. Malassezia, dandruff and seborrhoeic dermatitis: An overview. Br. J. Dermatol. 2011,
165, 2–8.
2. Turner, G.A.; Hoptroff, M.; Harding, C.R. Stratum corneum dysfunction in dandruff. Int. J.
Cosmet. Sci. 2012, 34, 298–306.
3. Gaitanis, G.; Magiatis, P.; Hantschke, M.; Bassukas, I.D.; Velegraki, A. The Malassezia genus in
skin and systemic diseases. Clin. Microbiol. Rev. 2012, 25, 106–141.
4. Warner, R.R.; Schwartz, J.R.; Boissy, Y.; Dawson, T.L., Jr. Dandruff has an altered stratum
corneum ultrastructure that is improved with zinc pyrithione shampoo. J. Am. Acad. Dermatol.
2001, 45, 897–903.
5. Bin Saif, G.A.; Ericson, M.E.; Yosipovitch, G. The itchy scalp—Scratching for an explanation.
J. Eur. Exp. Dermatol. 2011, 20, 959–968.
6. Ya-Xian, Z.; Suetake, T.; Tagami, H. Number of cell layers of the stratum corneum in normal
skin-relationship to the anatomical location on the body, age, sex and physical parameters.
Arch. Dermatol. Res. 1999, 291, 555–559.
7. O’goshi, K.; Iguchi, M.; Tagami, H. Functional analysis of the stratum corneum of scalp skin:
Studies in patients with alopecia areata and androgenetic alopecia. Arch. Dermatol. Res. 2000,
292, 605–611.
8. Myles, K.; Kalb, J.T.; Lowery, J.; Kattel, B.P. The effect of hair density on the coupling between
the tactor and the skin of the human head. Appl. Ergon. 2015, 48, 177–185.
9. Zhai, H.; Fautz, R.; Fuchs, A.; Bhandarkar, S.; Maibach, H.I. Human scalp irritation compared to
that of the arm and back. Contact Dermatitis 2004, 51, 196–200.
10. Essick, G.; Guest, S.; Martinez, E.; Chen, C.; McGlone, F. Site-dependent and subject-related
variations in perioral thermal sensitivity. Somatosens. Mot. Res. 2004, 21, 159–175.
11. Mehrabyan, A.; Guest, S.; Essick, G.; McGlone, F. Tactile and thermal detection thresholds of the
scalp skin. Somatosens. Mot. Res. 2011, 28, 31–47.
12. Rukwied, R.; Zeck, S.; Schmelz, M.; McGlone, F. Sensitivity of human scalp skin to pruritic stimuli
investigated by intradermal microdialysis in vivo. J. Am. Acad. Dermatol. 2002, 47, 245–250.
13. Masson, E.A.; Veves, A.; Fernando, D.; Boulton, A.J.M. Current perception thresholds: A new,
quick, and reproducible method for the assessment of peripheral neuropathy in diabetes mellitus.
Diabetologia 1989, 32, 724–728.
Cosmetics 2015, 2 393
14. Baquis, G.D.; Brown, W.F.; Capell, J.T.; Chaudhry, V.; Cros, D.; Drexinger, B.; Gelblum, J.B.;
Gilchrist, J.M.; Gitter, A.J.; Haig, A.J.; et al. Technology review: The Neurometer
®
Current
Perception Threshold (CPT). Muscle Nerve 1999, 22, 523–531.
15. Kobayashi, H.; Kikuchi, K.; Tsubono, Y.; Tagami, H. Measurement of electrical current
perception threshold of sensory nerves for pruritus in atopic dermatitis patients and normal
individuals with various degrees of mild damage to the stratum corneum. Dermatology 2003, 206,
204–211.
16. Lee, E.; An, S.; Lee, T.R.; Kim, H.K. Development of a novel method for quantitative evaluation
of sensory skin irritation inhibitors. Skin Res. Technol. 2009, 15, 464–469.
17. Parra, J.L.; Paye, M. EEMCO guidance for the in vivo assessment of skin surface pH.
Skin Pharmacol. Appl. Skin Physiol. 2003, 16, 188–202.
18. Tagami, H. Location-related differences in structure and function of the stratum corneum with
special emphasis on those of the facial skin. Int. J. Cosmet. Sci. 2008, 30, 413–434.
19. Mori, T.; Ishida, K.; Mukumoto, S.; Yamada, Y.; Imokawa, G.; Kabashima, K.; Kobayashi, M.;
Bito, T.; Nakamura, M.; Ogasawara, K.; et al. Comparison of skin barrier function and sensory
nerve electric current perception threshold between IgE-high extrinsic and IgE-normal intrinsic
types of atopic dermatitis. Br. J. Dermatol. 2010, 162, 83–90.
20. Tominaga, M.; Ozawa, S.; Tengara, S.; Ogawa, H.; Takamori, K. Intraepidermal nerve fibers
increase in dry skin of acetone-treated mice. J. Dermatol. Sci. 2007, 48, 103–111.
21. Florence, P.; Cornillon, C.; D’arras, M.F.; Flament, F.; Panhard, S.; Diridollou, S.; Loussouarn, G.
Functional and structural age-related changes in the scalp skin of Caucasian women. Skin Res.
Technol. 2013, 19, 384–393.
22. Saint-Martory, C.; Roguedas-Contios, A.M.; Sibaud, V.; Degouy, A.; Schmitt, A.M.; Misery, L.
Sensitive skin is not limited to the face. Br. J. Dermatol. 2008, 158, 130–133.
23. Misery, L.; Sibaud, V.; Ambronati, M.; Macy, G.; Boussetta, S.; Taieb, C. Sensitive scalp: Does
this condition exist? An epidemiological study. Contact Dermatitis 2008, 58, 234–238.
24. Misery, L.; Rahhali, N.; Ambonati, M.; Black, D.; Saint-Martory, C.; Schmitt, A.M.; Taieb, C.
Evaluation of sensitive scalp severity and symptomatology by using a new score. J. Eur. Acad.
Dermatol. Venereol. 2011, 25, 1295–1298.
© 2015 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/4.0/).
... Itchiness, measured using the VAS, improved significantly at weeks 2 and 4 ( Figure 6), and the MRA gradually and significantly increased at weeks 2 and 4 ( Figure 7A). The average TEWL value of all subjects at week 0 was consistent with the TEWL value of healthy scalp skin (6.6±1.6 g/ m 2 ·hour) 21 and there were no significant changes during the test period ( Figure 7B). ...
Article
Full-text available
Objective Dry and scaly conditions on the scalp are often observed in patients with atopic dermatitis, seborrheic dermatitis and/or pityriasis capitis. Those scalp lesions often exhibit low barrier function and reduced ceramide levels. Therefore, a clinical study was conducted to evaluate the efficacy of topical application of a pseudo-ceramide and eucalyptus extract-containing lotion on the scalps of patients with skin diseases. Methods Thirty-four subjects participated in this study (atopic dermatitis: 19 subjects; seborrheic dermatitis: 6 subjects; pityriasis capitis: 9 subjects). After 4 weeks of daily treatment with a pseudo-ceramide and eucalyptus extract-containing lotion, the skin symptoms had significantly improved in all patients with those skin diseases. Results Skin dryness, scaling, and erythema were significantly improved by treatment with the lotion. The moisture-retention ability of the scalp was significantly increased and itchiness, evaluated using a visual analog scale, decreased significantly. Accompanying those improvements was a significant improvement in the quality of life of the subjects, evaluated by the Skindex-16®. Conclusion From these results, we conclude that this pseudo-ceramide and eucalyptus extract-containing lotion effectively improved the dry and scaly conditions of the scalp as well as the quality of life of subjects with atopic dermatitis, seborrheic dermatitis, or pityriasis capitis.
Article
Background Various sebum levels can be detected in dandruff‐affected scalps. However, few studies have compared the biophysical characteristics of dandruff scalps categorized based on sebum levels. Aims To investigate and compare the biophysical characteristics of dandruff‐affected scalps categorized based on sebum levels. Methods Fifty‐four Korean women with dandruff and 30 healthy Korean women underwent physiological measurements, including evaluation of sebum and hydration levels, pH, and transepidermal water loss (TEWL) in the scalp. The levels of the biomarkers of interleukin‐8 (IL‐8) and kallikrein 5 (KLK5) and corneodesmosomes were investigated in the stratum corneum (SC) of the scalp. Results Dandruff was categorized as dry (low‐sebum, n = 25) or oily (high‐sebum, n = 29) based on a sebum cutoff level of 97.82 μg/cm². Both dry and oily dandruff‐affected scalps showed significantly decreased hydration levels and increased pH and TEWL compared with healthy subjects, with hydration levels being lower in dry dandruff‐affected scalps. IL‐8 expression was significantly increased in the oily dandruff‐affected scalp. In addition, both dry and oily dandruff‐affected scalps showed significantly increased KLK5 levels in the SC, with the levels being higher in oily dandruff‐affected scalps. Altered distribution of corneodesmosomes, present on the entire surface area of the corneocytes, was notable in oily dandruff‐affected scalps. Conclusion The biophysical characteristics of the two types of dandruff represent the influence of different characteristics, including hydration levels, expression of IL‐8 and KLK5, and corneodesmosome distribution. Thus, strategies to reduce dandruff levels should differ according to sebum levels.
Article
Full-text available
Many people suffer from scalp hair problems such as dandruff, folliculitis, hair loss, and oily hair due to poor daily habits, imbalanced nutritional intake, high stress, and toxic substances in their environment. To treat these scalp problems, dedicated services such as scalp hair physiotherapy have emerged in recent years. This article proposes a deep learning-based intelligent scalp inspection and diagnosis system, named ScalpEye, as an efficient inspection and diagnosis system for scalp hair physiotherapy as part of scalp healthcare. The proposed ScalpEye system consists of a portable scalp hair imaging microscope, a mobile device app, a cloud-based artificial intelligence (AI) training server, and a cloud-based management platform. The ScalpEye system can detect and diagnose four common scalp hair symptoms (dandruff, folliculitis, hair loss, and oily hair). In this study, we tested several popular object detection models and adopted a Faster R-CNN with the Inception ResNet_v2_Atrous model in the ScalpEye system for image recognition when inspecting and diagnosing scalp hair symptoms. The experimental results show that the ScalpEye system can diagnose four common scalp hair symptoms with an average precision (AP) ranging from 97.41% to 99.09%.
Article
Full-text available
Background Ageing of the skin, being chronological or sun induced is highly documented. Scalp, as a specific skin site, has, however, received little attention. This work attempted to describe functional and structural alterations that occur in scalp skin with ageing. Methods Two different age groups (N=15 each; 303 and 622 y.o. respectively) of Caucasian women participated in the study. Some functional parameters (TEWL, Sebum level, Hydration, T degrees) were recorded on the vertex part of the scalp, after having cut the hair flat on the scalp surface. Imaging of some structural criteria was carried out using high-frequency ultrasound technique and optical coherence tomography on the same scalp site and on the mid-forehead, as a close control skin site. ResultsAs compared with the younger group, the scalp of older women significantly showed a decreased TEWL and a slightly lower T degrees. The thickness of total skin (epidermis+dermis) increased with age on both scalp and on forehead. The thickness of scalp epidermis decreased with age while not significantly altered on forehead. Pseudoattenuation of ultrasound images increased in the older age group. Other criteria, such as sebum level, stratum corneum hydration, stratum corneum thickness, were not found altered with age. Conclusion With ageing, some few functional and structural changes are observed in the scalp of Caucasian women. Similarities or differences with those previously reported in other skin sites are discussed.
Article
Full-text available
Dandruff is characterized by a flaky, pruritic scalp and affects up to half the world's population post-puberty. The aetiology of dandruff is multifactorial, influenced by Malassezia, sebum production and individual susceptibility. The commensal yeast Malassezia is a strong contributory factor to dandruff formation, but the presence of Malassezia on healthy scalps indicates that Malassezia alone is not a sufficient cause. A healthy stratum corneum (SC) forms a protective barrier to prevent water loss and maintain hydration of the scalp. It also protects against external insults such as microorganisms, including Malassezia, and toxic materials. Severe or chronic barrier damage can impair proper hydration, leading to atypical epidermal proliferation, keratinocyte differentiation and SC maturation, which may underlie some dandruff symptoms. The depleted and disorganized structural lipids of the dandruff SC are consistent with the weakened barrier indicated by elevated transepidermal water loss. Further evidence of a weakened barrier in dandruff includes subclinical inflammation and higher susceptibility to topical irritants. We are proposing that disruption of the SC of the scalp may facilitate dandruff generation, in part by affecting susceptibility to metabolites from Malassezia. Treatment of dandruff with cosmetic products to directly improve SC integrity while providing effective antifungal activity may thus be beneficial. © 2012 Unilever PLC. ICS © 2012 Society of Cosmetic Scientists and the Société Française de Cosmétologie.
Article
Full-text available
In the last 15 years, the genus Malassezia has been a topic of intense basic research on taxonomy, physiology, biochemistry, ecology, immunology, and metabolomics. Currently, the genus encompasses 14 species. The 1996 revision of the genus resulted in seven accepted taxa: M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, and M. slooffiae. In the last decade, seven new taxa isolated from healthy and lesional human and animal skin have been accepted: M. dermatis, M. japonica, M. yamatoensis, M. nana, M. caprae, M. equina, and M. cuniculi. However, forthcoming multidisciplinary research is expected to show the etiopathological relationships between these new species and skin diseases. Hitherto, basic and clinical research has established etiological links between Malassezia yeasts, pityriasis versicolor, and sepsis of neonates and immunocompromised individuals. Their role in aggravating seborrheic dermatitis, dandruff, folliculitis, and onychomycosis, though often supported by histopathological evidence and favorable antifungal therapeutic outcomes, remains under investigation. A close association between skin and Malassezia IgE binding allergens in atopic eczema has been shown, while laboratory data support a role in psoriasis exacerbations. Finally, metabolomic research resulted in the proposal of a hypothesis on the contribution of Malassezia-synthesized aryl hydrocarbon receptor (AhR) ligands to basal cell carcinoma through UV radiation-induced carcinogenesis.
Article
The purpose of this study was to determine the effect of hair density on vibration detection thresholds associated with the perception of low frequency vibration stimuli applied to the head. A host of tactile sensitivity information exists for other parts of the body, however the same information is lacking for the head. Thirty-three college students, age 18-35, were recruited for the study. A mixed design was used to evaluate the effect of hair density, head location, and frequency on vibration detection thresholds. Results suggest that hair density might slightly impede vibration signals from reaching the scalp and reduce vibration sensitivity, for the least sensitive locations on the head. This research provides design recommendations for head-mounted tactile displays for women and those with hair that can be used to convey directional cues for navigation and as alerts to critical events in the environment. Published by Elsevier Ltd.
Article
CPT is a device for evaluating and quantifying sensory function which has been available in the medical market place for some years. The AAEM is currently undertaking a review of the general topic of quantitative sensory testing (QST), and technology reviews of other specific methodologies and instruments are anticipated in the future. The Neurometer ® CPT is a transcutaneous electrical stimulator which delivers sinusoidal electrical stimuli via surface electrodes at frequencies of 5 Hz, 250 Hz, and 2000 Hz, and at a current intensity range of 0.01 to 9.99 milliamperes. It is the only commercially available instrument applying this technology to the evaluation of sensory nerve function. Patients are asked to identify the presence or absence of the stimulus through a forced choice protocol. After an initial tentative threshold is determined, stimuli are presented that vary around the presumed threshold to confirm threshold stability and replicability. To prevent guessing, results are verified with placebo stimulation. The placebo stimulation is given by turning off all current without informing the patient and presenting these absent stimuli. Therefore, determination of threshold requires consistent patient response. The threshold of perception is the measured response. The testing procedure requires a brief time to perform (the promotional literature suggests 15 to 20 minutes), uses few consumable supplies, and will print
Article
From their original description, fungi of the genus Malassezia (previously Pityrosporum) have been associated with dandruff and seborrhoeic dermatitis. The principle evidence on which this connection was based was that the organisms were present, often in high numbers, on the skin in these conditions and that both responded to treatment that inhibited or destroyed Malassezia yeasts. The availability of new tools such as genomic and proteomic analyses has begun to provide a new insight into the pathogenetic mechanisms involved. New evidence shows the production of specific phospholipases on affected skin sites in dandruff and signalling molecules such as malassezin in seborrhoeic dermatitis. It is still not clear why those individuals and skin sites, prone to either disease, are particularly associated with the presence of these marker molecules but these studies are providing clues to the different ways in which organisms, which are normally commensals, interact with human skin.
Article
Scalp pruritus is a common complaint that is considered a diagnostically and therapeutically challenging situation. Scalp skin has a unique neural structure that contains densely innervated hair follicles and dermal vasculature. In spite of the recent advances in our understanding of itch pathophysiology, scalp itching has not been studied as yet. In this review, we summarize the current knowledge on the neurobiology of scalp and hair follicles as well as itch mediators and provide a putative mechanism for scalp itch with special emphasis on neuroanatomy and pathophysiology.
Article
The tactile and thermal sensitivity of diverse regions of the human body have been documented extensively, with one exception being the scalp. Additionally, sensory changes may accompany the hair loss from the scalp in androgen-related alopecia (ARA), but formal quantitative sensory testing (QST) has not been reported in respect of this. Therefore, light touch detection thresholds were obtained at nine scalp sites and one forehead site, using Semmes-Weinstein filaments (Von Frey hairs), and for warming and cooling from skin baseline temperature, using 28 and 256 mm(2) thermodes. Affective, thermal, and nociceptive sensations experienced at thermal detection threshold were quantified. Thirty-two male participants were recruited, 10 of whom had normal hair coverage, 12 of whom had shaved scalp but with potentially normal hair coverage, and 10 of whom exhibited ARA to some extent. The scalp was relatively insensitive to tactile and thermal stimulation at all tested sites, especially so along the midline and near the apex of the skull. Threshold level warm stimuli were rated less pleasant, the less sensitive the test site. After correction for age-related changes in sensitivity, bald scalp sites were found more sensitive to cooling than the same sites when shaved, consistent with prior informal reports of increased sensitivity for some scalp sensations in ARA. QST on hair-covered sites was subject to methodological issues that render such testing non-ideal, such as bias in measurement of resting skin temperatures, and the near impossibility of delivering filament stimuli to the scalp skin without disturbing neighboring hairs.
Article
Among localizations of sensitive skin, scalp is one of the less known. We performed a study for a better understanding of sensitive scalp and proposed a new score: the 3S score. An opinion poll was conducted on 2117 persons, which were representative of the French population. The total score was obtained by multiplying score severity of abnormal sensations by the number of these sensations. About one-third of the population declared to suffer from a sensitive scalp. It was increasingly frequent with age. The 3S questionnaire allowed discrimination among subjects with slightly sensitive, sensitive and very sensitive scalps. Itching and prickling were the most frequent symptoms. Sensitive scalp was sometimes associated with some scalp diseases. Dandruff cannot be considered as a symptom of sensitive scalp. This study is only the third reported study about sensitive scalp. The 3S questionnaire is a convenient and effective tool for investigating the severity and symptomatology of the sensitive scalp.
Article
Sensory skin irritation is regarded as one of the most serious side effects of cosmetic use. Thus, it is desirable to develop good inhibitors of sensory skin irritation. However, it is difficult to quantify the effect of sensory skin irritation inhibitors. We investigated the possibility of using an electrical current perception threshold (CPT) measurement for the quantitative evaluation of these inhibitors. We divided study populations into stinger and non-stinger groups based on their response to 5% lactic acid and assessed CPT values at 2000, 250, and 5 Hz on the cheek. Stingers showed significantly lower CPT values than non-stingers did at 250 and 5 Hz. We also measured CPT values before and after the application of nine materials with inhibitory effects on sensory skin irritation. To investigate the relationship between the change in CPT values and the effect of each material in the clinical stinging test, we conducted the stinging test with the test materials in a 5% lactic acid solution and with a 5% lactic acid solution (positive control). There was a positive correlation between the change in CPT values and the inhibitory effect that each material had on the stinging test. The change in CPT values can be used for the quantitative evaluation of sensory skin irritation inhibitors .