ArticlePDF Available

The Impact of Shampoo Wash Frequency on Scalp and Hair Conditions


Abstract and Figures

Background: How frequently should the scalp and hair be cleansed? A dearth of objective data has led to confusion both among lay people and experts. Each extreme has potential detrimental effects: overcleaning may lead to surface damage while undercleaning may lead to buildup of harmful stimuli. This situation is complicated because both objective and subjective criteria are relevant to assess optimal cleaning. Objectives: The objective of this work was to combine epidemiological and treatment data with both objective and subjective end points to yield clear data to guide both the consumer and expert as to optimal scalp and hair cleaning practices. Methods: Two studies were conducted with Asian populations without any specific scalp pathologies. An epidemiological study was conducted as a function of natural wash frequency. This was combined with a controlled wash frequency study. In both cases, objective measures of hair and scalp condition were assessed. These were combined with self-assessments of all participants. Results: In the epidemiological study, it was observed that overall satisfaction with hair and scalp condition was achieved when washing 5-6 times per week. This was consistent for both objective and subjective end points. Controlled treatment likewise showed that a daily wash regimen was superior to once per week cleansing for all end points. No objective detrimental effects to hair at this level of cleansing were observed. Conclusions: Two different studies led to the same conclusion: higher wash frequency is both beneficial and more preferred to lower wash frequency among the Asian populations studied. Concerns related to "overcleaning" were unfounded both objectively and subjectively.
This content is subject to copyright.
Clinical Investigations – Research Article
Skin Appendage Disord 2021;7:183–193
The Impact of Shampoo Wash Frequency
on Scalp and Hair Conditions
Supriya Punyani
a Antonella Tosti
b Maria Hordinsky
c Dawn Yeomans
James Schwartz
aThe Procter & Gamble Company, Singapore, Singapore; bDepartment of Dermatology and Cutaneous Surgery,
University of Miami, Miami, FL, USA; cDepartment of Dermatology, University of Minnesota, Minneapolis, MN, USA;
dThe Procter & Gamble Company, Mason, OH, USA
Received: September 28, 2020
Accepted: November 4, 2020
Published online: February 15, 2021
James Schwartz
The Procter & Gamble Company
8700 Mason-Montgomery Rd.
Mason, OH 45040 (USA)
schwartz.jr.2 @
© 2021 S. Karger AG, Basel
DOI: 10.1159/000512786
Shampoo frequency · Scalp · Hair · Oxidative stress ·
Epidemiological · Treatment
Background: How frequently should the scalp and hair be
cleansed? A dearth of objective data has led to confusion
both among lay people and experts. Each extreme has po-
tential detrimental effects: overcleaning may lead to surface
damage while undercleaning may lead to buildup of harmful
stimuli. This situation is complicated because both objective
and subjective criteria are relevant to assess optimal clean-
ing. Objectives: The objective of this work was to combine
epidemiological and treatment data with both objective and
subjective end points to yield clear data to guide both the
consumer and expert as to optimal scalp and hair cleaning
practices. Methods: Two studies were conducted with Asian
populations without any specific scalp pathologies. An epi-
demiological study was conducted as a function of natural
wash frequency. This was combined with a controlled wash
frequency study. In both cases, objective measures of hair
and scalp condition were assessed. These were combined
with self-assessments of all participants. Results: In the epi-
demiological study, it was observed that overall satisfaction
with hair and scalp condition was achieved when washing
5–6 times per week. This was consistent for both objective
and subjective end points. Controlled treatment likewise
showed that a daily wash regimen was superior to once per
week cleansing for all end points. No objective detrimental
effects to hair at this level of cleansing were observed. Con-
clusions: Two different studies led to the same conclusion:
higher wash frequency is both beneficial and more preferred
to lower wash frequency among the Asian populations stud-
ied. Concerns related to “overcleaning” were unfounded
both objectively and subjectively. © 2021 S. Karger AG, Basel
There are few questions in personal care that elicit
more debate than “How frequently should I use a sham-
poo?” The opinions can vary from one end of the spec-
trum (as infrequently as possible) to the other (daily). For
example, in one 3-month period, 2 relevant articles were
published in the New York Times – one suggesting hair
is washed too frequently [1] and the other suggesting the
exact opposite [2]. Consumers appear to be responding
more strongly to recommendations to reduce shampoo-
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
ing as declining shampoo wash frequency is observed in
industry habit and practice studies and documented in
the popular press [3, 4].
The reason for these divergent opinions is that little
objective data exists to facilitate informed decision-mak-
ing. For those recommending low wash frequency, the
most often cited reasons are beliefs that hair is damaged
due to surfactant-induced extraction of beneficial lipid
components and stimulation of excessive compensatory
scalp sebum production. Taken to the extreme, there are
those that recommend avoiding the use of shampoos al-
together; this has been colloquially termed “no poo.” At
the other end, those that recommend higher wash fre-
quencies usually assert the benefits of removing a wide
range of potentially detrimental “dirt” residues. This po-
sition is reinforced by acknowledging that scalp is just an
extension of the face, which is almost universally washed
at least daily.
The buildup of “dirt” on hair and scalp has multiple
origins: endogenous sources such as sebum excretion and
skin exfoliative processes as well as exogenous sources
such as certain hair treatment products, airborne pollu-
tion, and pollen as well as exposure to volatile materials
such as those arising from tobacco smoke. The covering
of the scalp by hair creates a unique skin surface micro-
environment that facilitates microbial growth (dark,
moist, and sebum rich), leading to a unique microbiome
[5]. These microbes use components of the “dirt” as food
sources which fuel their metabolic activity, enhancing
their impact on the underlying skin [6].
Existing Literature Relating Wash Frequency and
Scalp Condition
Decreased wash frequency results in longer accumula-
tion times for secreted sebum. Sebum begins to be chem-
ically altered as soon as it reaches the scalp surface; the
longer its residence time, the greater these modifications.
Specifically, modified sebum contains free fatty acids and
oxidized lipids, which are known to be irritating to skin
[6, 7].
Two extreme cases of low wash frequency have been
evaluated relative to scalp impact. An Antarctic research
team was monitored for changes in scalp microbe content
and resultant symptoms [8]; during the expedition, scalp
itch and flakes increased dramatically, which was also ac-
companied by a 2–3 order of magnitude increase in scalp
Malassezia levels. These same authors subsequently stud-
ied International Space Station astronauts [9] and found
a dramatic rise in Malassezia levels over time with them
as well.
Even in less-extreme low-wash-frequency situations,
impacts to scalp condition have been observed. In an ep-
idemiological work studying Caucasian, Chinese, and Af-
rican American individuals, lower shampoo wash fre-
quency was associated with a higher prevalence of scalp
issues such as dandruff [10]. Low wash frequency has also
been observed to result in increased prevalence of sebor-
rheic dermatitis in African Americans (AA) [11]. In a
treatment study of individuals having a normal habit of
low wash frequency and experiencing seborrheic derma-
titis or psoriasis, wash frequency was deliberately in-
creased, first with a cosmetic shampoo and then with a
scalp treatment product [12]. Increased wash frequency,
even if just using a cosmetic shampoo, resulted in de-
creased flaking, redness, itching, Malassezia amount, and
the level of inflammatory cytokines.
Sebum accumulation and itch severity was studied as
a function of time post-shampoo [13]. It was observed
that itch severity increased significantly during 72 h post-
shampoo, coincident with increases in sebum accumula-
tion, supporting the model that Malassezia metabolism
leads to the resultant accumulation of irritating stimuli
such as oxidized free fatty acids that initiate itch. Higher
scalp sebum levels have been shown generally to be re-
lated to the prevalence of scalp sensitivity [14], suggesting
a cause-and-effect relationship.
Existing Literature Relating Wash Frequency and
Hair Condition
There are less rigorous data available to address the
impact of low wash frequency on hair condition. In a
study of the consumer perception of hair quality ex-
pressed as good or bad “hair days,” it was found [15] that
lower wash frequency led to a higher frequency of “bad
hair days.” This was hypothesized to be due to an accu-
mulation of scalp sebum which is subsequently trans-
ferred to the hair leading to a general greasy appearance
characterized by oily shine and hair fiber-fiber adhesion.
In a comparative study of technical and perceived hair
quality between Caucasians and AA [16], it was found
that a much lower wash frequency amongst AA was as-
sociated with greater hair fragility and decreased growth
rates. Similar observations were reported in a study of
Nigerian females [17]. As mentioned above [11], sebor-
rheic dermatitis is also more prevalent in this group,
which has been demonstrated to impact the quality of
hair emerging from the scalp [18]. Scalp sensitivity, which
has been shown to be increased by low wash frequency
and accumulated sebum [14], has been shown to associate
with increased hair loss [19].
Shampoo Wash Frequency
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
Summary of Relevant Literature
A general interpretation begins to emerge from the
published literature. Low wash frequency allows scalp se-
bum level to increase as well as the proportion of chemi-
cally modified potentially harmful components within
the sebum (such as oxidized free fatty acids). This mate-
rial tends to increase the prevalence of scalp-related is-
sues, which can be manifested in common itch or more
defined etiologies such as seborrheic dermatitis. Either
directly or indirectly (via scalp-impacted hair growth ef-
fects), low wash frequency tends to have detrimental ef-
fects on hair, but much of this comes specifically from
evaluating AA hair and the typical low wash frequency
The Need for Objective Data
The increasing perception that shampoo has the po-
tential to harm the hair has led to a decrease in wash fre-
quency globally. Paradoxically, this behavior may have
the opposite effect on hair (and scalp). The research re-
ported herein is aimed at generating objective data relat-
ing wash frequency to resultant effects on scalp and hair
condition. We report here two studies aimed at adding
objective data to enable informed decisions of optimum
wash frequency. One is an epidemiological study while
the other is a treatment study, both of which combined
objective technical assessments with self-perception eval-
Materials and Methods
Epidemiological Study
Study Design
A 2-week epidemiological study was conducted in Xi’an, Chi-
na, with 1,500 healthy male and female subjects of Chinese ethnic-
ity with no known scalp pathologies, aged 18–75 years old after
obtaining the informed consent under the principles of Good Clin-
ical Practice (see Tables 1 and 2 for a summary of population de-
mographics and Fig.1 for a visual summary of hair textures). No
treatments were involved in this epidemiological study. Recruit-
ment resulted in 200–300 subjects in each wash frequency group:
≤1×/week, 2×/week, 3–4×/week, 5–6×/week and 7×/week. This
enabled the evaluation of the impact of wash frequency on scalp
and hair conditions. Figure 1 demonstrates the hair type and tex-
ture of recruited females in the epidemiological study.
Dandruff flaking severity was quantified using the Adherent
Scalp Flaking Score (ASFS) as described [20]. The baseline visit
included a self-perception assessment questionnaire designed to
capture subject-relevant outcomes (e.g., severity of scalp flaking)
using a categorical scale that varied from “none” to “very severe”
(0 = none, 1 = slight, 2 = slight to moderate, 3 = moderate, 4 =
moderate to severe, 5 = severe, and 6 = very severe). Subjects were
asked to refrain from shampooing and using any hair styling prod-
ucts prior to scheduled visits during which they underwent ASFS
measurement and completed self-assessment questionnaires.
Treatment Study
Study Design
This was a 5-week, double-blind, IRB-approved study conduct-
ed in Xi’an, China, with 60 healthy male and female participants
between the ages of 18–50 with no known scalp pathologies. En-
rolled subjects habitually washed their hair with low frequency (≤2
times per week) and refrained from use of scalp treatments, medi-
cations, hair oils, serums, or anti-dandruff shampoos in the past 4
weeks. The study was conducted under the principles of Good
Clinical Practice (see Table3 for a summary of population demo-
graphics). The study was divided into sequential phases, differing
in the frequency of use of a provided shampoo (a potentiated ZPT
scalp care shampoo [21]). The first phase of the study, lasting one
week, had one initial controlled shampoo application followed by
a refrain of 7 days with no shampoo use. The second phase of the
Table 1. Epidemiological-study wash-frequency population distri-
% wash frequency (male and female)
Age range,
week (daily)
18–30 68 79 20 2 0
31–45 24 15 27 15 7
46–60 7 6 43 55 56
61–75 1 0 10 28 37
Table 2. Epidemiological study wash frequency population hair
length distribution
Hair length Male, % Female, %
Close cut 87 2
Ear length 12 8
Ear length to shoulder length 1 13
Shoulder length 0 12
Greater than shoulder length 0 65
Table 3. Treatment clinical population parameters
Phase 1:
“7-day refrain”
Phase 2:
“daily wash”
Subjects, N60 60
Female, n (%) 56 (93) 56 (93)
Male, n (%) 4 (7) 4 (7)
Age, years, mean (SD) 43.4 (6.2) 43.4 (6.2)
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
study, lasting 4 weeks, comprised daily wash (controlled applica-
tion) with the same shampoo. Subjects refrained from the use of
any other scalp/hair products throughout the course of the study.
Hair Wash Protocol
Study personnel filled a 10 mL syringe with shampoo and ad-
justed water temperature between 32 and 38°C and flow rate at
5.1–6.3 L/min for hair wash. Subjects leaned over the front of the
shampoo station to wet their scalp completely. The shampoo was
dispensed equally across the subject’s entire head, after which the
subject gently massaged the shampoo into the entire scalp for 45 s.
Subject rinsed shampoo from their hair until water ran clear. Sub-
jects used a blow dryer to dry their hair.
Two assessment time points occurred: at the end of the 7-day
refrain period (“7-day refrain”) and 24 h after the last wash of 4
weeks of daily washing (“daily wash”). The 4-week period of daily
washing enabled enough time for new hair to grow and emerge
from the scalp under the new scalp condition resulting from daily
washing. For analysis of hair samples, the most recently grown seg-
ment (approximately 1 cm) was used.
Measures included technical measures and self-assessments of
both scalp and hair conditions. Most scalp assessments were made
directly on scalp or on extracts of the scalp surface. Hair samples
were collected from a 2.5 × 2.5 cm square area on both sides of the
scalp. At the end of phase 1, a template was used to mark the hair
collection area and a cosmetologist clipped the hair with scissors
and placed the hair in glassine envelopes, keeping the orientation
of the fiber bundle consistent. The hair collection procedure was
repeated at the end of phase 2 after 2 cm of new growth. For hair
analysis, the length of the sample was measured, and the portion
of the sample that was closest to the scalp (representing newest
growth) was utilized. An equal length of hair was cut from the
proximal end of the phase 1 hair sample. The phase 1 and 2 visits
included a self-perception assessment questionnaire designed to
capture subject-relevant outcomes (e.g., severity of scalp flaking)
using a categorical scale that varied from “none” to “very severe.”
Table 4 summarizes the measures, the details of which can be
found in the online suppl. Material (for all online suppl. material,
Fig. 1. Example of hair type and texture of recruited females in the epidemiological study.
Table 4. Summary of measures and methods used for the treatment study
Measure Method Sampling Description
Scalp flaking level Expert grading Direct visual Expert visual grading of scalp surface flakes
Scalp surface lipids FTIR Direct surface probe Spectroscopic identification of sebaceous lipids
Scalp odor Expert grading Direct sniffing Expert olfactory grading
Scalp surface visual Handheld microscope Direct surface probe Magnified scalp surface
Oxidative stress marker MS Scalp tape strip;
Hair direct extraction
Quantitation of oxidized linoleic acid (HODE)
Hair lipids GC Extract of cut hair Separation and quantitation of sebaceous and internal lipids
Hair water absorption DVS Directly on cut hair Gravimetric analysis; controlled humidity and temperature
Hair shine Gloss meter Directly on cut hair Evaluation of specular reflectance
Hair surface visual SEM Directly on cut hair Highly magnified hair surface
FTIR, Fourier-transform infrared spectroscopy; MS, mass spectroscopy; GS, gas chromatography; DVS, dynamic vapor sorption; SEM, scanning electron
Shampoo Wash Frequency
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
Statistical Analysis
After completion of the epidemiological and treatment study,
data were checked for accuracy and completeness. All subjects
were evaluated for compliance with study protocol at each visit,
and their evaluability was determined prior to database locking.
Statistical analyses were performed on evaluable data. Logarithm
transformation was applied to biomarker data prior to analysis to
stabilize the variance. A statistical test was determined to be sig-
nificant if a two-sided p value <0.05.
Scalp Technical Results (Epidemiological Study)
Scalp flaking severity, as determined by the ASFS
method, decreased significantly with increase in wash fre-
quency (Fig.2). These data represent the results of the
total panel and are independent of either age or gender
(online suppl. Table 1).
Scalp Condition Self-Perception Results
(Epidemiological Study)
Self-perception assessment questionnaires completed
for different wash frequencies revealed statistically sig-
nificant reduction in the severity of self-perceived scalp
dandruff, itch, and dryness with increases in wash fre-
quency (Fig.3). The reduction in scalp dandruff percep-
tion coincided with the improvements observed in tech-
nical dandruff severity based on the ASFS grading meth-
od. These data represent the results of the total panel and
are independent of either age or gender. Please refer on-
line suppl. Table 2 for total (male and female) and gender-
wise data.
Hair Condition Self-Perception Results
(Epidemiological Study)
Hair condition self-perception assessment revealed no
discernible negative outcomes as a result of increased
wash frequency. Specific parameters summarized in Fig-
ure 4 are hair loss, hair brittleness (both of which slightly
improved at high wash frequency), and hair smoothness.
Please refer online suppl. Table 3 for total (male and fe-
male) and gender-wise data.
A comprehensive parameter that reflects self-percep-
tion of hair condition was evaluated and termed “great
hair days,” representing the overall satisfaction of the
panelist with their hair look and feel. Using this metric,
the number of days per week a panelist has overall satis-
faction with their hair condition increases significantly
Scalp Flaking Score
≤1× 3–4×
Wash Frequency per week
5–6× Daily
Fig. 2. Scalp Flaking Score graded by experts as function of wash
frequency in epidemiological study. The mean ASFS is plotted
with standard error bars. Results not connected by same letter are
significantly different. ASFS, Adherent Scalp Flaking Score.
Scalp Issue Severity Perception
≤1× 3–4× 5–6×
Wash Frequency (times per week)
Fig. 3. Self-perceived scalp parameters dandruff, itch, and dryness
of n = 1,500 males and females as function of wash frequency in the
epidemiological study. The mean is plotted with standard error bars.
Results not connected by same letter are significantly different.
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
the more frequently they wash their hair (Fig.5). These
results were independent of age and gender. Please refer
online suppl. Table 4 for total (male and female) and gen-
der-wise data.
Scalp Condition Technical Results (Treatment Study)
Compared with the 7-day refrain period, daily wash
with a potentiated ZPT shampoo resulted in the expected
significantly lower amounts of overall scalp surface lipid
LS means ± SE
p = 0.0536
Normalized CH-stretch
Daily wash 7-day
Daily wash 7-day
Daily wash 7-day
Daily wash
LS means ±SE
p < 0.0001
(absolute amount)
LS means ± SE
p < 0.0001
LS means ± SE
p < 0.0001
a b cd
Fig. 6. Technical scalp measurements for total sebum lipids (normalized CH-stretch PA) (a), oxidized lipids
(HODE-9) (b), flaking score (ASFS) (c), and odor intensity at 7-day refrain (yellow bar) and daily wash (blue bar)
(d). For each measurement, lower value indicates healthier scalp. ASFS, Adherent Scalp Flaking Score.
Number of Great Hair Days Per Week (Mean)
≤1× 3
Wash Frequency (times per week)
Fig. 5. Self-perceived of number of “great hair days” improved for
n = 1,500 males and females as function of wash frequency. The
mean is plotted with standard error bars. Results not connected by
the same letter are significantly different.
Hair issue severity perception
3–4× 5–6× Daily
Wash frequency per week
a, b a, b
b, c
Hair loss
Hair brittle
Hair not smooth
Fig. 4. Self-perceived hair attributes hair loss, hair brittleness, and
hair not smooth of n = 1,500 males and females as function of wash
frequency in the epidemiological study. The mean is plotted with
standard error bars. Results not connected by the same letter are
significantly different.
Shampoo Wash Frequency
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
and fatty acid of sebum as measured on scalp (Fig.6a).
The level of a scalp health biomarker of oxidized lipid
(HODE) is also significantly reduced with daily wash ver-
sus 7-day refrain (Fig.6b). Even though the subjects were
not dandruff sufferers with high incoming flaking levels,
daily wash lowered the level of flaking on scalp as mea-
sured by ASFS (Fig.6c). Expert assessment of scalp odor
was also improved by the daily wash regimen relative to
the 7-day refrain (Fig.6d).
Images of the scalp were captured to visually sum-
marize the oil accumulation representative of the low
wash protocol and the improvement because of daily
wash. Representative sample images are summarized in
Figure 7.
Hair Condition Technical Results (Treatment Study)
The daily wash protocol resulted in significantly less
sebum on hair than the 7-day refrain as expected (Fig.8a).
Fig. 7. Selected scalp images comparing the
oil accumulation representative of the
7-day refrain and daily wash protocols.
LS means ± SE
Daily wash 7-day
Daily wash 7-day
Daily wash 7-day
Daily wash
p < 0.0001
Total sebum, μg/g
LS means ± SE
p < 0.0001
HODE-9 (normalized
by hair weight)
LS means ± SE
p < 0.0001
Greasy shine,
degree = 60
LS means ± SE
p < 0.0001
DVS–water uptake
at 90% RH
b c d
Fig. 8. Technical hair measurements for total sebum lipids (a), oxidized lipids (HODE) (b), greasy shine (c), and
% water uptake at 7-days refrain (yellow bar) and daily wash (blue bar) (d). For measurements in (a, b, d), lower
value indicates healthier hair. For measurement in (c), lower value indicates a less greasy shine on hair.
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
Evaluation of the proportion of sebum that has been oxi-
dized (using the established biomarker HODE), it was ob-
served that daily wash resulted in significantly less oxida-
tion (Fig.8b), both paralleling the scalp results. Measure-
ment of greasy hair shine demonstrated daily wash left
the hair with a less oily (specular) shine (Fig.8c). Finally,
use of DVS to probe hair cuticular surface integrity and
daily wash resulted in lower hair water vapor absorption
indicating a more effective cuticular barrier (Fig.8d).
Images of the hair were captured to visually summa-
rize the oil accumulation representative of the low wash
protocol and the improvement because of daily wash.
Representative sample images are summarized in Fig-
ure 9.
Internal hair lipids were quantified using GC method
to determine whether the two wash protocols affected the
amount of beneficial internal hair lipids. There were no
significant differences observed between the 7-day re-
Total Internal Lipids (μg/g of hair)
Internal Fatty
Internal Wax
Total Internal
Hair Lipids
7-Day Refrain
Daily Wash
Fig. 10. Quantification of internal hair lipids using GC method as a result of 7-day refrain and daily wash proto-
cols. No significant differences were observed.
Daily wash
BMI 346 1.0 kV 10.5 mm × 500 SE(UL) 11/28/2018
BMI 346 1.0 kV 10.5 mm × 1.00k SE(UL) 11/28/2018
100 μm
50.0 μm
Fig. 9. Selected hair images comparing the
oil accumulation representative of the
7-day refrain and daily wash protocols.
Shampoo Wash Frequency
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
frain and daily wash protocols in any of the classes of in-
ternal hair lipids (Fig.10).
Self-Perception Evaluation (Treatment Study)
Validating the objective technical assessments, self-as-
sessments indicate whether subjects noticed the impact of
these technical measures on scalp and hair properties. All
attributes evaluated had dramatic improvements upon
transition from the 7-day refrain to the daily wash proto-
col (in some cases, over half of the full rating scale). While
the reduction in oil buildup on both hair and scalp are
likely obvious, the interpretations of the implications are
less obvious: improved perception of hair health and at-
tributes related to it and reduced scalp irritation and itch.
The results are summarized in Figure 11.
The question “How frequently should scalp and hair
be washed?” has been difficult to answer definitively due
to lack of relevant objective technical information. There
are concerns among both professionals as well as con-
sumers that washing with surfactant-based products has
the potential to harm either or both the hair and scalp. We
sought to generate data, both technical and panelist self-
assessed, to understand the impact of wash frequency on
the resultant conditions of both hair and scalp. Two dif-
ferent study designs were conducted to address this ques-
tion. In one study (the Epidemiological Study), wash fre-
quency varied based on the normal habits and practices
of a recruited population. A second study (the Treatment
Study) was conducted in a population of low-frequency
shampooers, who were switched to a higher frequency of
shampooing for 1 month. These studies substantially and
uniquely add to the existing literature to enable informed
decision-making regarding optimum wash frequency for
hair and scalp care.
Impact of Wash Frequency on Scalp Condition
In the Epidemiological Study, those washing with a
higher frequency experienced less flaking as judged both
by experts as well as self-perceived less flaking, itch, and
dryness. In the Treatment Study, switching from low to
high wash frequency resulted in significant decreases in
the technical parameters of scalp sebum level, degree of
flaking, amount of oxidized sebaceous lipids, and scalp
odor. These were accompanied by corresponding self-
perceived improvements in these same attributes as well
as more composite parameters (such as irritation).
The data from these two studies are entirely consistent
with the studies existing already [10–12] supporting the
observation that increased wash frequency results in de-
creased scalp flaking and itching. These studies, however,
extend the beneficial scalp impacts to considerably more
technical and self-assessment measures. For example,
new measures of decreased oxidative stress (using the
biomarker HODE) may add to the mechanistic explana-
tions as to why sebum accumulation on the scalp is gen-
erally detrimental to its condition. This work also extends
Better during refrain Better during wash
Delta improvement
Scalp attributesHair attributes
a b
Fig. 11. Improvement of self-perception of hair (a) and scalp (b) attributes upon switching from 7-day refrain
versus daily wash protocol. A categorical scale 0–10 was used for the worst of the conditions panelists had during
the last 24 h, where 0 = none and 10 = worst imaginable. p values are based on pairwise t test.
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
the symptomatic observations to include malodor gen-
eration. Taken together, there is a strong group of data
that consistently supports the understanding that low
wash frequency allows sebum to accumulate, become
progressively chemically modified and irritating leading
to increased prevalence of resultant symptoms (flakes,
itch, and dryness). A significant aspect of the irritation
likely originates from the formation and accumulation of
species such as oxidized lipids that lead to oxidative stress
[22]. These observations are consistent in both technical
measures and individual self-assessments. As a whole, the
data support that increased scalp washing is beneficial for
both normal scalps as well as those exhibiting pathologies
such as seborrheic dermatitis.
Impact of Wash Frequency on Hair Condition
While the conclusions regarding the detrimental impact
of low wash frequency on scalp condition are widely ac-
cepted, the impact on hair condition is considerably more
controversial, largely due to the paucity of existing data. In
the Epidemiological Study, the panelists observed no nega-
tives to hair condition with increased wash frequency and
the trend was always in the direction that increased wash
frequency decreased hair issues. Smooth feel perception
did not statistically significantly improve, but both hair loss
perception and brittleness perception did significantly im-
prove with increasing wash frequency. These attributes,
and likely many more, can be combined into a global col-
loquial term “great hair days.” [15] Using this global metric,
increasing wash frequency resulted in dramatic improve-
ment of overall hair satisfaction: 2 or less washes per week
resulted in less than 3 great hair days per week whereas
daily washing led to over 5 great hair days per week.
In the Treatment Study, objective technical parameter
measurement provides important insights to definitively
address the impact of wash frequency on hair condition.
Reduction of sebum level and greasy shine are to be ex-
pected. As with the scalp, a reduction in oxidative stress
has been observed with increased wash frequency. The
relationship between the oxidative stress status of the
scalp and resultant oxidative stress of the hair has been
previously established [18] and has been confirmed here,
with wash frequency being the driver of improved condi-
tions of both. Continuing the parallel, the hair obtained
from those with higher wash frequency was in better con-
dition in that the protective cuticular barrier was more
functionally effective, enabling reduced water vapor ab-
sorption. Again, this has previously been observed as a
result of reduced oxidative stress to scalp and resultant
hair produced from it [23].
An important measure of impact of treatments on hair
condition is the impact on internal lipids that build the
cuticular structure. Harsh treatments are known to cause
the reduction of these beneficial lipids [24]. Removal of
these beneficial lipids has been shown to cause greater
roughness, permeability, and reduced structural integrity
[25]. Shampoo products can be formulated to inhibit any
such effects [26]. In the treatment study, daily wash for 28
days with a well-formulated, mild scalp care shampoo
showed that no significant loss in internal lipids occurred
as a result of increased wash frequency. The subjects in
this study self-assessed their condition as dramatically
better at the higher wash frequency: reduced oiliness,
more healthy, less frizz, less dull, less dry, and reduced
Taken together, the data from these two studies strong-
ly support the conclusion that increased wash frequency
is beneficial to self-perceived hair condition and not det-
rimental to technically assessed hair quality for the Asian
population studied. One of the primary technical con-
cerns reported with excessive washing has been loss of
internal beneficial lipids; this was not observed in this
work. Both of these studies consisted of Asian individuals
with straight or low-texture hair (visually exemplified in
Fig.1). It is not known whether the results observed here
are generalizable to hair types with much higher texture/
curl. However, preliminary data from an epidemiological
study involving Nigerian women demonstrated higher
wash frequency was associated with less hair complaints
[27]. It is also possible that greater use of styling imple-
ments than used in these studies could contribute to hair
damage separate from washing itself.
These two studies significantly increase the rigorous
objective data available to assess the impact of shampoo
wash frequency on scalp and hair conditions. There is
little doubt that increased wash frequency is beneficial to
scalp condition. However, the data also strongly support
that for the Asian populations studied, hair condition is
not negatively affected by increased wash frequency and
that the self-perception is toward marked improvement.
The overall model of detrimental effects of sebum, espe-
cially oxidized versions, is consistent with other observa-
tions relating scalp to hair health. Thus, these data should
serve as an important asset to offset the unfounded con-
cerns that high shampoo wash frequency is detrimental
in any way.
Shampoo Wash Frequency
Skin Appendage Disord 2021;7:183–193
DOI: 10.1159/000512786
We acknowledge A. Yu for clinical trial management. The fol-
lowing individuals made various analytical measures: S. Whitaker,
H. Kang, L. Li, A. Ritter and H. Lau. Statistics were performed by
X. Ying and L. Xu.
Statement of Ethics
Studies were conducted in concordance with the World Medi-
cal Association Declaration of Helsinki. All subjects provided in-
formed, written consent. The treatment study was reviewed and
approved by Beijing Health Tech Research Co., Ltd. as study CSD
Conflict of Interest Statement
S.P. and J.S. are employees of the Procter & Gamble Company,
which paid 100% of the costs of this work.
Funding Sources
These studies were funded by the Procter & Gamble Company.
Author Contributions
All authors contributed equally to study design, data interpre-
tation, and drafting the manuscript.
1 Tuminoct R. How often should you really
wash your hair? New York Times. 2016 Oct
2 Shapiro B. Are you not washing your hair
enough? New York Times. 2017 Jan.
3 Morley K. Women are washing their hair less
than three times a week for the first time in a
decade. The Telegraph. 2017 Feb 15.
4 Kent E. Shampoo sales fall by £23million over
the past year because women who work at
home don’t bother to wash their hair. Daily
Mail. 2016 Dec 19.
5 Grice EA, Segre JA. The skin microbiome. Nat
Rev Microbiol. 2011; 9(4): 244–53.
6 DeAngelis YM, Gemmer CM, Kaczvinsky JR,
Kenneally DC, Schwartz JR, Dawson TL Jr.
Three etiologic facets of dandruff and sebor-
rheic dermatitis: Malassezia fungi, sebaceous
lipids, and individual sensitivity. J Investig
Dermatol Symp Proc. 2005; 10(3): 295–7.
7 Chiba K, Kawakami K, Sone T, Onoue M.
Characteristics of skin wrinkling and dermal
changes induced by repeated application of
squalene monohydroperoxide to hairless
mouse skin. Skin Pharmacol Appl Skin Physi-
ol. 2003; 16(4): 242–51.
8 Sugita T, Yamazaki T, Yamada S, Takeoka H,
Cho O, Tanaka T, et al. Temporal changes in
the skin Malassezia microbiota of members of
the Japanese Antarctic Research Expedition
(JARE): a case study in antarctica as a pseudo-
speace environment. Med Mycol. 2015; 53:
9 Sugita T, Yamazaki T, Makimura K, Cho O,
Yamada S, Ohshima H, et al. Comprehensive
analysis of the skin fungal microbiota of astro-
nauts during a half-year stay at the interna-
tional space station. Med Mycol. 2016; 54(3):
10 Schwartz J, Cardin C, Dawson T Jr. Dandruff
and seborrheic dermatitis. 3rd ed. In: Baran R,
Maibach H, editors. Textbook of cosmetic
dermatology. New York: Taylor & Francis;
2005. p. 259–72.
11 Roseborough IE, McMichael AJ. Hair care
practices in African-American patients. Se-
min Cutan Med Surg. 2009; 28(2): 103–8.
12 Kobayashi M, Ito K, Sugita T, Murakami Y,
Yamashita R, Matsunaka H, et al. Physiologi-
cal and microbiological verification of the
benefit of hair washing in patients with skin
conditions of the scalp. J Cosmet Dermatol.
2016; 15(4): e1.
13 Kato K. Studies on sebum on scalp and sham-
poo: time-lapse changes in the amounts of tri-
glyceride and free fatty acid on the scalp and
subjective symptoms for one week. Sanarwa
ta Kwalejin Fasaha ta Jami’a ta Hokkaido.
1997; 10: 47–58.
14 Ma L, Guichard A, Cheng Y, Li J, Qin O,
Wang X, et al. Sensitive scalp is associated
with excessive sebum and perturbed microbi-
ome. J Cosmet Dermatol. 2019; 18(3): 922–8.
15 Birch MP, Messenger A. ‘Bad hair days’, scalp
sebum excretion and the menstrual cycle. J
Cosmet Dermatol. 2003; 2(3–4): 190–4.
16 Lewallen R, Francis S, Fisher B, Richards J, Li
J, Dawson T, et al. Hair care practices and
structural evaluation of scalp and hair shaft
parameters in African American and Cauca-
sian women. J Cosmet Dermatol. 2015; 14(3):
17 Ayanlowo O, Otrofanowei E. Hair care prac-
tices, scalp disorders and psychological effects
on women in Nigeria. Washington, DC: An-
nual Meeting of the American Academy of
Dermatology; 2019.
18 Schwartz JR, Henry JP, Kerr KM, Flagler MJ,
Page SH, Redman-Furey N. Incubatory envi-
ronment of the scalp impacts pre-emergent
hair to affect post-emergent hair cuticle integ-
rity. J Cosmet Dermatol. 2018; 17(1): 105–11.
19 Misery L, Rahhali N, Ambonati M, Black D,
Saint-Martory C, Schmitt AM, et al. Evalua-
tion of sensitive scalp severity and symptom-
atology by using a new score. J Eur Acad Der-
matol Venereol. 2011; 25(11): 1295–8.
20 Bacon RA, Mizoguchi H, Schwartz JR. Assess-
ing therapeutic effectiveness of scalp treat-
ments for dandruff and seborrheic dermatitis,
part 1: a reliable and relevant method based
on the adherent scalp flaking score (ASFS). J
Dermatolog Treat. 2014; 25(3): 232–6.
21 Schwartz JR, Bacon RA, Shah R, Mizoguchi
H, Tosti A. Therapeutic efficacy of anti-dan-
druff shampoos: a randomized clinical trial
comparing products based on potentiated
zinc pyrithione and zinc pyrithione/climba-
zole. Int J Cosmet Sci. 2013; 35(4): 381–7.
22 Trüeb RM, Henry JP, Davis MG, Schwartz JR.
Scalp condition impacts hair growth and re-
tention via oxidative stress. Int J Trichology.
2018; 10(6): 262–70.
23 Schwartz JR, Henry JP, Kerr KM, Mizoguchi
H, Li L. The role of oxidative damage in poor
scalp health: ramifications to causality and as-
sociated hair growth. Int J Cosmet Sci. 2015;
37(Suppl 2): 9–15.
24 Masukawa Y, Tsujimura H, Tanamachi H,
Narita H, Imokawa G. Damage to human hair
caused by repeated bleaching combined with
daily weathering during daily life activities.
Exog Dermatol. 2004; 3(6): 273–81.
25 McMullen RL, Laura D, Chen S, Koelmel D,
Zhang G, Gillece T. Determination of physi-
cochemical properties of delipidized hair. J
Cosmet Sci. 2013; 64(5): 355–70.
26 Marsh JM, Brown MA, Felts TJ, Hutton HD,
Vatter ML, Whitaker S, et al. Gel network
shampoo formulation and hair health bene-
fits. Int J Cosmet Sci. 2017; 39(5): 543–9.
27 Ayanlowo O, Otrofanowei E. Hair care prac-
tices, scal disorders and psychological effects
on women in Nigeria. Washington DC: An-
nual Meeting of The American Academy of
Dermatology; 2019.
... Daily skin damage caused by hard brushing, hair friction and exposure to irritants in skin and hair products are also likely involved in predisposing individuals to SD, although the relative contributions and importance of each is not entirely known [57]. In regards to 'over washing', interesting new work has demonstrated that a daily washing protocol in a Chinese population results in the greatest reduction in flaking and improvement in scalp health [58], however further studies should be conducted to extend this finding to other populations, such as those living in drier climates where daily washing may lead to xerosis. ...
... In clinical studies, there is typically a washout phase of several days or weeks followed by a test phase where ZnPT is compared against either an inactive shampoo (as negative control) or another treatment (e.g., ketoconazole or selenium sulfide). Studies can be conducted in separate treatment arms or as a half-head design, where participants use [58]. Can be combined with other agents such as steroids or other antifungal classes (such as piroctone olamine) in recalcitrant or severe cases. ...
... Agents should not be used for>2-4 weeks as there is a greater risk of side effects (2fold compared to azoles) [58]. Skin symptoms can include telangiectasia, striae, dermatitis (mainly burning and itch), and atrophy [60]. ...
Seborrheic dermatitis (SD) is a common dermatological disorder with symptoms that include skin flaking, erythema and pruritus. This review discusses the topical products available for treating SD, which target several aspects of disease pathobiology, including cutaneous microbial dysbiosis (driven by Malassezia yeast), inflammation, sebum production and skin barrier disruption. Among the various treatments available, zinc pyrithione (ZnPT) based products that exhibit anti-fungal action are the market leaders. A skin compartment approach is presented here for combining ZnPT exposure information with threshold levels for anti-fungal efficacy and toxicity, overall providing a comprehensive picture of ZnPT therapeutics and safety. While Malassezia yeast on the surface are effectively targeted, yeast residing beyond the superficial follicle may not receive adequate ZnPT for anti-fungal effect and may continue to grow, forming the basis for skin re-colonisation. Levels entering systemic circulation from topical delivery are well below toxic thresholds, however the elevated zinc levels within the viable epidermis warrants further investigation. Strategies to improve formulation design can be broadly classified as influencing 1) topical delivery, 2) therapeutic bioactivity, 3) skin mildness, and 4) sensory attributes. Successful SD treatment ultimately requires formulations that can balance efficacy, safety, and consumer appeal.
... Although synthetic surfactants are typically added to shampoo for foaming and washing purposes, frequent usage of these substances can cause dry hair, hair loss, scalp irritation, and eye discomfort 3 . Herbal shampoo alternatives are being researched, although it might be challenging to create cosmetics utilizing only natural ingredients 4 . Numerous medicinal herbs are known to have positive benefits on hair and are frequently used into shampoo formulations 5 . ...
Full-text available
The study's objectives were to create a pure herbal shampoo, assess its physicochemical qualities, and compare them to those of commercially available synthetic shampoos. The formulation of the herbal shampoo involved combining readily accessible at-home extracts of Reetha, Henna, Neem, Amla, almond powders, Alovera gel and tulsi lemon juice to a 10% aqueous gelatin solution. The pH was then corrected with citric acid. Nine distinct formulations were created using various amounts of each herb's extract. To ascertain the physicochemical characteristics of both produced and marketed shampoos, a number of tests including visual inspection, pH, wetting time, percentage of solid components, foam volume and stability, surface tension, detergency, filth dispersion, etc., were carried out. By giving 20 student volunteers a blind test, the conditioning effect of the herbal shampoo formulation was also assessed. The herbal shampoo was presented simply and appealingly. After 5 minutes, it demonstrated strong detergency and cleaning, low surface tension, tiny bubble size, and good foam stability. The homemade and store-bought shampoos displayed comparable findings for the percentage of solid ingredients. 3.0 out of 4 was the rating for the conditioning performance of the hair after using a herbal shampoo, compared to 3.4 and 3.3 for commercial synthetic shampoo. The outcomes showed that the specially made shampoo performed excellently in terms of conditioning, on par with shampoo readily accessible in stores. Nevertheless, more study and development are needed to increase its quality and safety.
Full-text available
Hair and scalp care are among the daily hygiene rituals. There is a wide range of hair products on the Czech market designed for washing or adjustment of hair appearance. This article aims to introduce the basic categories of functional products for hair and scalp, in particular shampoos, conditioners, and hair tonics. The range of presented cosmetics is extended by medicinal preparations and medical devices utilized in the hair and scalp treatment. The review also provides practical advice for pharmacists and pharmaceutical assistants about hair products usage, as proper education of the patient/client by expending person increases the effectiveness of applied products.
Full-text available
Introduction: The scalp hairs on an average African is dry with low tensile strength and a tendency to break easily. This is mostly due to poor penetration of the natural oils on the scalp and the very curly hair texture. Various techniques developed to manage African hair are associated with certain hair and scalp disorders and are sources of distress. Objectives: This was a cross-sectional survey to compare natural African hair and chemically processed (relaxed) hair to determine the effect of hair care and grooming practices on common scalp disorders and the psychological effect in Nigerian women. Subjects and methods: Questionnaires were administered to women at the market, churches and outreaches with many women in attendance to document the hair grooming practices, common scalp symptoms and psychological effects experienced. They were also examined for the presence of seborrhoeic dermatitis and traction alopecia. Results: The study involved 452 women (62.17%) with relaxed hair and 275 women (37.83%) with natural (untreated) hair. Women with relaxed hair experienced significantly more flaking of the scalp (P = 0.046, x2 = 6.16), hair breakage (P = 0.023, x2 = 11.35) and hair loss (P = 0.020, x2 = 7.87) than those with natural hair. The most common psychological effects of hair scalp disorders in all participants were feeling of uneasiness 142 (19.5%), frustration 49 (6.7%), poor body image 40 (5.5%) and anger 38 (5.2%). Significantly more women with relaxed hair experienced moderate hair loss from traction than women with natural hair (P = 0.014, x2 = 8.52). Conclusion: Nigerian women experienced clinical and psychological distress consequent to their hair grooming practices. Individuals with relaxed hair had more physical symptoms, hair loss and psychological disturbances than those with natural hair.
Full-text available
Conventionally, the medical focus has been either on hair loss or the condition of the scalp in terms of specific dermatological diseases. Indeed, the proximate structural arrangement of the scalp and hair leads to an interdependent relationship between the two. While protective benefits of the hair to the scalp are obvious, the role of the scalp as an incubatory environment for the preemergent hair fiber has largely been ignored. In fact, there is a wealth of observational data on specific dermatological conditions of the scalp providing evidence for the role of the scalp condition in supporting the production of healthy hair. Oxidative stress, the inability of the body to sufficiently counteract the sources of oxidation, is prevalent in many skin conditions, including normal skin aging. On the scalp, the hair appears to be impacted prior to emergence, and oxidative stress appears to play a role in premature hair loss. The scalp commensal organism, Malassezia, has been recognized to be a source of oxidative damage. Therefore, hair care products, specifically shampoos, with active Malassezia inhibitory agents, such as zinc pyrithione, tend to reduce premature hair loss, besides the known benefits in treating specific dermatologic scalp pathologies, and therefore should represent an integral part of every treatment regimen for hair loss, even in individuals not showing symptoms of scalp pathologies. © 2019 International Journal of Trichology | Published by Wolters Kluwer - Medknow.
Full-text available
Objective: The objective of this work was to create a shampoo formula that contains a stable ordered gel network structure that delivers fatty alcohols inside hair. Methods: X-ray diffraction (SAXS and WAXS), SEM and DSC have been used to confirm formation of the ordered Lβ gel network with fatty alcohol (cetyl and stearyl alcohol) and an anionic surfactant (SLE1S). Micro autoradiography and extraction methods using GC-MS were used to confirm penetration of fatty alcohols into hair and cyclic fatigue testing was used to measure hair strength. Results: In this work evidence of a stable Lβ ordered gel network structure created from cetyl and stearyl alcohol and anionic surfactant (SLE1S) is presented and this is confirmed via scanning electron microscopy images showing lamella layers and differential scanning calorimetry (DSC) showing new melting peaks vs the starting fatty alcohols. Hair washed for 16 repeat cycles with this shampoo showed penetration of fatty alcohols from the gel network into hair as confirmed by a differential extraction method with GC-MS and by radiolabeling of stearyl alcohol and showing its presence inside hair cross-sections. The gel network role in delivering fatty alcohol inside hair is demonstrated by comparing with a shampoo with added fatty alcohol not in an ordered gel network structure. The hair containing fatty alcohol was measured via the Diastron cyclic fatigue instrument and showed a significantly higher number of cycles to break vs control. Conclusions: The formation of a stable gel network was confirmed in the formulated shampoo and it was demonstrated that this gel network is important to deliver cetyl and stearyl alcohol into hair. The presence of fatty alcohol inside hair was shown to deliver a hair strength benefit via cyclic fatigue testing. This article is protected by copyright. All rights reserved.
Summary Background: Sensitive scalp, one of the most frequent complaints among sensitive skin syndrome, has been described as abnormal and unpleasant sensory reactions of the scalp to environmental stimulus. However, the symptoms are usually objective and hard to diagnose. Objective: This study aimed to reveal the biophysical properties and etiology of sensitive scalp. Methods: Sixty‐two healthy female subjects were enrolled and divided into nonsen-sitive scalp (NS) and sensitive scalp (SS) groups according to questionnaires. Nonin-vasive instruments were used to measure biophysical properties. Ultra‐performance liquid chromatography‐tandem mass spectrometry and gas chromatography mass spectrometry were introduced to quantify skin lipids profiles, and 16S rRNA sequencing was used to detect the composition of bacteria. Results: Sensitive scalp showed elevated pH level, more irritated skin, and more flu-orescence of porphyrins. Increased sebum production was found in SS group at occiput, among which free fatty acids, cholesteryl ester, and squalene were signifi-cantly in higher amount compared with NS. SS also had significantly higher percent-age of Propionibacterium, and lower bacterial diversity. Conclusions: Taken together, sensitive scalp showed disrupted barrier function, abnormal sebum amount and composition, as well as perturbed microbiome, which might be the direct cause. Products targeting these features could be helpful for the treatment of sensitive scalp.
Objectives: To determine whether the oxidative stress transmitted to newly grown hair from an unhealthy scalp has physical consequences to the cuticular condition and function. Methods: A uniquely designed 24-week clinical study included 8 weeks of pretreatment with a cosmetic shampoo and 16 weeks of treatment with either a potentiated zinc pyrithione (ZPT) antidandruff shampoo or a placebo cosmetic shampoo. This clinical design allowed the growth and acquisition of hair samples under conditions of varying but known scalp health as a result of treating a dandruff/seborrheic dermatitis (D/SD) population. Two complementary methods were used to characterize the integrity of the cuticular surface. Hair surface hydrophobicity was assessed by quantifying water wetting force using a Wilhelmy balance method. Surface structure and porosity were assessed using dynamic vapor sorption (DVS) to gravimetrically quantify water sorption. Results: Chemical oxidative stress to pre-emergent hair has been shown to have negative consequences to hair surface structure. Compared to a placebo shampoo control, use of a potentiated ZPT shampoo improved scalp health and significantly improved the following attributes associated with healthy hair: hair surface hydrophobicity (surface energy) and cuticular moisture barrier effectiveness (dynamic vapor sorption). Conclusions: Pre-emergent hair can be negatively impacted by the oxidative stress that occurs with an unhealthy scalp, possibly due to metabolic activity of resident microbes. Manifestations of the oxidative stress include altered cuticle surface properties that are responsible for its protective function; these effects are similar in type to those observed by bleaching post-emergent hair. These alterations have the potential to make the hair, once emerged from the scalp, more susceptible to the cumulative physical and chemical insults responsible for hair feel and look, fiber integrity, and overall retention.
Background: It is unclear whether hair washing is effective against scalp eruption and pruritus caused by seborrheic dermatitis or psoriasis vulgaris. Aims: To assess whether a proper hair-washing regimen, including the use of antibacterial shampoo, can ameliorate scalp eruption symptoms and alter the composition of the scalp microflora. Methods: Eighteen patients with seborrheic dermatitis or psoriasis vulgaris scalp eruptions were instructed in proper techniques of daily hair washing, rinsing, and shampooing, which they underwent for 12 weeks. They used control shampoo in weeks 1-4 and 9-12, and an antibacterial shampoo during weeks 5-8. At the start of the test period and at weeks 4, 8, and 12, we assessed scalp symptoms (erythema, scaling/desquamation, dryness, itchiness, and scratching scars); microbial DNA levels from lesion and nonlesion areas; and levels of interleukin (IL)-1α, IL-1ra, and total protein in the scalp's horny layer. Results: Compared to baseline values, scaling/desquamation and itchiness improved significantly at weeks 8 and 12. Other observed skin symptoms also improved over time. Malassezia colonization levels in lesion and nonlesion areas decreased gradually; the decrease was significant at week 8 in lesion areas and at weeks 4 and 8 in nonlesion areas. Bacterial colonization levels also decreased gradually, achieving significance in lesion areas at week 4. Gradual decreases in IL-1ra/IL-1α level showed statistical significance at weeks 4 and 12, while the protein quantity significantly decreased at week 12. Conclusion: Proper hair washing improved scalp condition symptoms, and possibly the underlying etiology.
The International Space Station (ISS) is a huge manned construct located approximately 400 km above the earth and is inhabited by astronauts performing space experiments. Because the station is within a closed microgravity environment, the astronauts are subject to consistent stress. This study analyzed the temporal changes in the skin fungal microbiota of 10 astronauts using pyrosequencing and quantitative PCR assay before, during, and after their stay in the ISS. Lipophilic skin fungi, Malassezia predominated most samples regardless of the collection period, body site (cheek or chest), or subject. During their stay in the ISS, the level of Malassezia colonization changed by 7.6- ± 7.5-fold (mean ± standard deviation) and 9.5- ± 24.2-fold in cheek and chest samples, respectively. At the species level, M. restricta, M. globosa, and M. sympodialis were more abundant. In the chest samples, the ratio of M. restricta to all Malassezia species increased, whereas it did not change considerably in cheek samples. Fungal diversity was reduced, and the ratio of Malassezia to all fungal colonization increased during the astronauts’ stay at the ISS. The ascomycetous yeast Cyberlindnera jadinii was detected in abundance in the in-flight sample of 5 of the 10 astronauts. The microorganism may have incidentally adhered to the skin during the preflight period and persisted on the skin thereafter. This observation suggests the ability of a specific or uncommon microorganism to proliferate in a closed environment. Our study is the first to reveal temporal changes in the skin fungal microbiota of ISS astronauts. These findings will provide information useful for maintaining the health of astronauts staying in the space environment for long periods and for preventing infection due to the human skin microbiota.
The oxidative stress element of unhealthy scalp leads to compromised pre-emergent hair formation and poorly formed hair as it grows. Only cosmetic solutions can minimize the impact of unhealthy hair and to achieve healthy looking and feeling hair, the scalp health must be normalized first. The objectives of this research were to both investigate whether oxidative stress was a relevant aetiological element in scalp dandruff and seborrhoeic dermatitis and whether scalp condition affects the quality of hair that grows from it. Further, this research was designed to determine whether an effective anti-dandruff shampoo would repair and protect the scalp and pre-emergent hair from oxidative stress. This study demonstrated that oxidative stress is an aetiological element relevant to the dandruff condition and that a potentiated ZPT shampoo effectively improves scalp condition, including a reduction in oxidative stress. The compromised hair condition associated with dandruff is concomitantly improved when the scalp condition is improved. It appears that there is a direct link between hair quality and scalp health.
How African American hair fragility relates to hair care practices and biologic differences between races is not well understood. To assess the differences between perceptions of hair health, hair care practices, and several biologic hair parameters between Caucasian and African American women. A questionnaire on perceptions of hair health and hair care practices was administered. Biological and structural parameters of hair shaft and scalp, including growth, density, diameter, cycle, breakage, and scalp blood flow were also assessed in this case-control study. Significant differences between the Caucasian and African American women were observed in the questionnaire and biologic study data. Regarding self-reported perceptions of hair health, there were differences in the following: hair shaft type (P < 0.001), hair breakage (P = 0.040), and desire to change hair (P = 0.001). Regarding self-reported hair care practices, there were differences in the following: location of haircutting (P = 0.002) and washing (P = 0.010), washing frequency (P < 0.001), chemical relaxer use (P < 0.001), hooded hair dryer use (P < 0.001), and hair shaft conditioner use (P = 0.005). The two groups had similar practices in regard to the use of hair color, frequency of hair color use, chemical curling agents, and handheld blow dryer use. Regarding biological and structural parameters, there were differences in the following: hair growth rate (P < 0.001), density (P = 0.0016), diameter (P = 0.01), number of broken hairs (P < 0.001), and blood flow (P = 0.03). There was no significant difference in hair cycle parameters.The differences in hair care practices and hair fiber morphology among African American women may contribute to clinically observed variation in hair fragility and growth. © 2015 Wiley Periodicals, Inc.
The International Space Station (ISS) is located approximately 400 km above the Earth. Astronauts staying at the ISS are under microgravity and are thus unable to bathe or shower; instead, they wash their bodies using wet tissues. For astronauts, skin hygiene management is important to maintain the quality of life during long-term stays on the ISS. In Antarctica, members of a Japanese geological investigation team negotiate their way over land using snowmobiles. During their 3-month stay, they are subject to a "pseudo-space" environment similar to that experienced by ISS astronauts, including the inability to bathe or shower. In this study, temporal changes in the colonization levels of skin lipophilic fungi, Malassezia were investigated in 16 team members. Compared to the levels before their trip to Antarctica, the fold changes in Malassezia colonization levels during the researchers' stay in Antarctica were in the range of 3.0 ± 1.9 to 5.3 ± 7.5 in cheek samples, 8.9 ± 10.6 to 22.2 ± 40.0 in anterior chest samples, 6.2 ± 5.4 to 16.9 ± 25.5 in behind-the-ear samples, and 1.7 ± 0.9 to 17.4 ± 33.4 in sole-of-the-foot samples. On the scalp, the level of Malassezia colonization increased dramatically, by 96.7 ± 113.8 to 916.9 ± 1251.5 fold. During their stay in Antarctica, the team members experienced itchy scalps and produced a large number of scales. The relative proportions of Malassezia globosa and M. restricta shifted to seborrheic dermatitis/dandruff types. These results provide useful information for the development of skin hygiene management plans for astronauts staying at the ISS. © The Author 2015. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: