Journ al of Cosmetics, Derm atolog ical Sciences a nd Applications, 2014, 4, 24-30
Published Online February 2014 (
Is the P hotosut uring Agent, Rose Bengal, a Mutagen?
Lindsey Hunter-El lul1, Shuguang Wang2, Jeffrey Wickliffe2, Michael Wilkers on1
1Department of Dermatology, The University of Texas Medical Branch, Galveston, Texas, USA; 2Department of Global Environ-
mental Heal th Sciences, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, USA.
Received December 11th, 2013; revised January 9th, 2014; accepted January 17th, 2014
Copyright © 2014 Lindsey Hunter-Ellul et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In accordance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the
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Rose Bengal (RB) is a potential photosuturing agent that may improve standard dermatologic surgical closure
techniques. However, RB produces reactive oxygen species with photoactivation and its photomutagenic poten-
tial must be considered in clinical application. We investigated cytotoxicity, mutagenicity, and singlet oxygen (SO)
productio n of RB on epit helial Chinese ha mster ovary cell line. Cells were exposed to RB concentrations: 0.1%,
0.01%, 0.001%, 0.0001%, 0.00001%; irradiated for 400 s using a high-intensity visible wavelength lamp or
maintained in the dark. Cell viability was assessed by XTT assay, mutagenicity by HPRT gene mutation assay,
and SO pro duction by Sens or Green reagent . RB > 0.001% was significantly cytotoxic. Viabilities were uninflu-
enced by ≤0.0001% RB controls, or 30-min incubation. 49% of irradiated cells died after 24-h in 0.0001% RB. At
≥0.001% RB, >90% of cells died. Irradiating 0.00001% - 0.001% RB inc reased SO; lev els dropped sig nificantly
between 0.01% - 0.1%. Controls exhibited negligible SO production. HPRT suggested that RB was not muta-
genic (0.0001%, 0.00001%); SO induction increased between 0.00001% - 0.001%, with reduced production at
higher concentrations. Pilot studies suggested irradiated 0.0001% RB is mutagenic in vitro; current data suggest
RB is not photomutagenic. The contribution of RB’s cytotoxicity on observed clinical improvement of scars and
mutagenic potential remains unclear, necessitating further study.
Rose Bengal; Photochemical Tissue B onding; Mutagenicity; Cytotoxicity; Wound Healing;
Dermatological Surgery
1. Introduction
Wound healing and scar formation are researched exten-
sively, and especially important to dermatological sur-
gery. Skin incisions and excisions are closed b y a variety
suture types, staples, wound closure strips, and adhesives.
However, recent research shows promise in improved
epidermal wound closure and healing with a p hotoche m-
ical tissue bonding (PTB) agent, 0.1% Rose Bengal
(RB;4,5,6,7-tetrachloro-2’,4’,5’,7’-te traiodo -fluorescein)
suspended in phosphate buffered saline (PBS), when
applied to wound edges and activated by green laser light
[1,2]. Upon photoactivation, Rose Bengal may behave as
a sort of “nanosuture,” as the dye may crosslink proteins
bet wee n ti ss ues s ur fa ce s ther e b y sea li n g ski n wo und s [ 2 ].
Rose Bengal does not appear to be phototoxic in porcine
skin ex vivo or rabbit skin in vivo [3]. However, pr evious
studies have demonstrated that photoactivated RB ge-
nerates reactive oxygen species (ROS), including singlet
oxygen (1O2), which promote lipid peroxidation, DNA
damage, cell membrane damage, and can cause cell death
[4,5]. In this study, we investigated toxicity, mutagenici-
ty, and singlet oxygen production of photoactivated Rose
Bengal using epi theli al cells in cult ure.
Rose Bengal, a fluorescein derivative, is a historical
Ophthalmologic stain used to aid in diagnosing ocular
surface disorders. RB absorbs and is excited by green
wavel engths (~532 nm) leading to a tissue bonding reac-
tion when appli ed to wound edges via an unkno wn mech-
anism. Photoactivating RB may aid in wound closure,
improve wound healing, promote skin graft adhesion,
and cell viability appears unaffected [1,2,6]. There are
Is the Photosuturing Agent, Rose Bengal, a Mutagen?
many potential benefits of PTB, including simplicity,
rapidity, and painlessness. Further, PTB could avoid su-
ture removal, foreign body reactions, additional tissue
injury, and infection. The first in-human clinical trial of
RB-induced PTB was recently completed in 2009. Re-
sults showed that PTB provided adequate tensile strength
preventing wound dehiscence and less inflammation
compared to sutures, and may also reduce scarring [7].
Research shows photoactivated RB’s ability to cross-
link collagen scaffolds and found this is effective for
producing strong, stable collagen microstructures with
improved physiochemical scaffold properties [8]. PTB is
hypothesized to work via a light-initiated covalent cross-
linking of proteins between the wound surfaces, leading
to the immediate formation of a relatively impermeable
seal [7,9,10]. When excited states of the activated photo-
sensitizer and photoproducts (e.g., ROS) are formed, they
interact with pr oximal bio molecules (e.g., amino acids in
collagen) leading to their photoexcitation. Photoexcited
biomolecules can then react with adjacent side chains
for ming co vale nt p rotein -protein crosslinks [11-13]. Pho-
toactivated RB reaction has shown to favor the produc-
tion of 1O2 (~75%), the remainder being primarily super-
oxide anion radicals (20%) [14].
As a photosensitizer molecule in an aerobic environ-
ment, RB ’s activatio n b y eithe r ultraviole t o r visib le li ght
irradiation leads to its excited singlet state (Figure 1)
[12,15]. Each photosensitizer (PS) molecule has the po-
tential to generate 103 - 105 1O2 molecules prior to re-
duction with 1O2 or by another reaction, thus exhausting
the cycle [12]. With this capacity to regenerate until
reacting with proximal biomolecules or auto-exhaustion,
there is ample potential for activated photosensitizers to
create harmful ROS.
In patients treated with intralesional RB chemo-abla-
tion for subcutaneous melanoma metastases, systemic
phototoxicity has been observed [16]. Using RB on
HaCat keratinocytes, the production of 1O2 has been
found using a spectrophotometer in photosensitized cells.
Again, RB’s potential for mutagenicity was not assessed
[17]. Because RB can enter living cells and stain the
nucleus, this raises questions about mutagenicity, espe-
cially since studies have demonstrated that byproducts of
Rose Bengal are capable of interacting with and damag-
ing DNA [18,19]. This study examines the cytotoxicity
and mutagenicity associated with photoactivated RB in
hopes of gaining a better insight into the potential ha-
zards associated with the use of RB in PTB procedures.
Figure 1. Photosensitization Cycle. PS = Photosensitizer;
1PS* = PS excited singlet state; 3PS* = PS excited triplet
state; hv = energy of a photon of UV or visible radiation
2. Materials and Methods
Chinese hamster ovary cells (CHO), a mammalian epi-
thelial cell line with fibroblast-like and epithelial-like
morphology, were obtained from American Type Cell
Culture (Manassas, Virginia). Fetal bovine serum (FBS),
Ham’s F-12, L-glutamine, penicillin/streptomycin, 0.05%
tryps in-EDTA solution, and Singlet Oxygen Sensor
Green were purchased from Invitrogen (Frederick, MD).
6-thioguanine (6-TG) and 2,3-bis[2-Methoxy-4-nitro-5-
sulfophenyl]-2H-tetrazoliu m-5-caboxyanilide (XTT) were
purchase from Sigma-Aldrich (St. Louis, MO). Phos-
phate buffered saline (PBS) and methanol were pur-
chased from Fisher Scientific (Houston, TX). Crystal
violet was purchased from Acros Organics (Geel, Bel-
gium). The high-intensity visible light (81,500 lux; Mas-
tech Digital 4-Range 200,000 Lux Meter, Model:
LX1330B) with a 65 Watt fluorescent bulb was pur-
chased from a hardware store.
2.1. Cell Culture and Treatment
CHO cells were cultured in Ham’s F-12 medium sup-
plemented with 10% FBS, 1% L-glutamine, and 1% pen-
icillin/streptomycin in 25 cm2 culture flasks in a dark,
humidified incubator at 37˚C with 5% CO2. Cells were
maintained under exponential growth conditions and RB
suspended in Ham’s F-12 was added to control and RB
flasks at the time of light irradiation, creating 0%, 0.1%,
0.01%, 0.001%, 0.0001%, or 0.00001% RB concentra-
tions. All exposure groups were maintained in duplicate
cult ures a nd hand led i n dar k lightin g, avoid ing R B photo-
2.2. Light Irradiation
Cells were suspended in Ham’s F-12 with RB and irra-
diated for 400 seconds to high-intensity visible light
(~400 - 700 nm), using a 65 Watt fluorescent bulb (T-
max 33.9˚C at 400 seconds) by placing culture flasks on
glass 3 cm above the bulb [15]. Controls remained in the
2.3. Cell Viability
Trypan Blue staining was used for initial cell counts to
assist in calculating appropriate cell quantities necessary
for each of the assays used. Cell viability was assessed
using the XTT assay (TOX2) according to the manufac-
turer’s protocol (Sigma-Aldrich), to assess mitochond rial
dehydrogenase activity. After 30 minutes or 24 hours
post light irradiation, 20 μL of activated XTT solution
was added to the cells, then incubated for 3 hours. Six
replicates for each exposure concentration were ex-
amined. Background absorption was eliminated by cen-
trifuging plates at 200× g for 5 minutes and supernatant
was transferred to a new plate. Absorbance at 450 nm
PS hv 1PS* 3PS*PS + O2(1g)
Is the Photosuturing Agent, Rose Bengal, a Mutagen ?
(corrected at 690 nm) was measured using a microplate
spectrophotometer (Bio-RAD Benchmark Plus).
2.4. HPRT Gene Mutation Assay
The HPRT mutation assay and methods for calculating
plating efficiency and mutation frequencies followed
Gupta and Singh’s technique [20]. The assay was re-
peated for each test condition 3 separate times, using 3
plates to determine plating efficiency and 6 plates for
6TG resistance. Cells were maintained in the dark incu-
bator for 5 days to select for mutant colonies, replacing
complete medium once on day 3 of incubation. On day 5,
medium was removed, cells were rinsed with PBS,
stained with Cresyl violet, and colonies were counted.
2.5. Singlet Oxygen Production
Test concentrations of RB (0%, 0.1%, 0.01%, 0.001%,
0.0001%, or 0.00001%) were suspended in Ham’s F-12
or PBS. 10 μL of 5 mM Sensor Green (SG) reagent was
added to 90 μL of the range of RB solutions, and 100 μL
of RB-SG solution were pipetted into 96-well tissue cul-
ture plates, 3 replicates for each concentration with and
without light irradiation. Controls were covered with
aluminum foil d uring and afte r light irradia tion, avoiding
irradiation. The F-12/SG and PBS/SG plates were irra-
diated for 0, 200, or 400 seconds. Specimens were eval-
uated for ROS using a fluorescence microplate reader
(Fluostar Optima, BMG Labtech) at the following set-
tings: Excitation 485 nm, Emission 520 nm, Position 3,
“Fluoresc ence.”
2.6. Data Analysis
Dose-response relationships for the examined endpoints
were statistically tested using a general linear model
(univariate analysis of variance procedure) in SPSS ver-
sion 16.0 for Windows. Post-hoc mean comparisons were
conducted using a Bonferroni correction for multiple
comparisons. P-value <0.05 was used to determine sig-
3. Resul ts
3.1. XTT Assay
Viability was unaffected at 0.0001% RB in Ham’s F-12
with and without light irradiation after 30 minutes of
incubation (Figure 2). Nearly 45% of cells were lost
after light irradiation and 24 hours of incubation with
0.0001% RB (Figure 3). Over 90% of cells died when
exposed to 0.001% up to 0.1% RB in Ham’s F-12 re-
gardless of light irradiation, after 30 minutes and 24
hours of incubation. There appeared to be significant
dose-dependent negative effects (p < 0.01) in viabilities.
Figure 2. Cell viability was determined by the XTT assay
after 30 minutes of incubation. The results were expressed
as a perce ntage of t he readi ng in control w ells. The mean ±
SD are from two independent exper iments.
Figure 3. Cell viability was determined by the XTT assay
after 1440 minutes (24 hours) of incubation. The results
were expressed as a percentage of the reading in control
wells. The mean ± SD are from two independent experi-
3.1.1. No Light, 30 Minutes Incubation
There was no difference between the control and the
lowest dose (0.0001% RB); however, comparing these to
the higher concentrations in this group, controls and
0.0001% RB were significantly different from all other
concentrations (p < 0.01 ), with viabilities greatl y reduced
in the latter concentrations. There were no significant
differences amongst other concentrations.
3.1.2. Light, 30 Minutes Incubation
Simi lar fi ndings o ccurr ed wit hin this group a s in the “No
Light” group above. There was no difference between the
control and the lowest dose (0.0001% RB). Comparing
these concentrations to higher concentrations in this
group, controls and 0.0001% RB were significantly dif-
ferent from all other concentrations (p < 0.01), with
greatly reduced viabilities in the latter. There were no
significant differences a mong st other concentrations.
3.1.3. No Light, 1440 Minutes (24 Hours)
of Incubation
Similar findings occurred here as in the “No Light” and
Is the Photosuturing Agent, Rose Bengal, a Mutagen?
“Light, 30 Minutes of Incubation” groups in F igure 2.
There was no difference between controls and lowest
dose (0.0001% RB), however, comparing these to the
remaining concentrations in this group, controls and
0.0001% RB were significantly different from all other
concentrations (p < 0.01) with greatl y reduced viabilitie s
in the latter concentrations. There were no significant
differences amongst other concentrations.
3.1.4. Light, 1440 Minutes (24 Hours) of Incubation
Controls were significantly different from all other con-
centrations (p < 0.01), with viabilities showing a slight
increase after irradiation with light. Additionally, the
lowest dose (0.0001% RB) differed from all other con-
centrations (p < 0.01), where the irradiated group had
nearly 50% reduction in viability compared to the group
without irradiation. There was no difference amongst all
other concentrations.
3.2. HPRT Gene Mutation Assay
The initial HPRT gene mutation assay revealed that irra-
diating cells with 0.0001% RB suspended in Ham’s F-12
was likely mutagenic, with roughly a doubling of the
mutant frequency above background (Figure 4). A repeat
study including 0.00001% RB did not appear to be mu-
tagenic at 0%, 0.00001%, or 0.0001% RB in Ham’s F-12
regardless of irradiation status (Figure 5). Higher con-
centrations were cytotoxic and the assay was not per-
3.3. Singlet Oxygen Production
The Sensor Green Assay detected 1O2 production by RB
in PBS (Figure 6) or Ham’s F-12 (Figure 7) at varying
concentrations with and without light irradiation for 0,
200, or 400 seconds.
3.3.1. Sensor Green Assay in PBS Buffer
1) PBS, No Light
Controls, 0.00001%, 0.0001%, or 0.001% RB did not
Figure 4. Mutation frequencies at the hgprt locus in CHO
cells induced by 0%, 0.0001%, and 0.001% RB suspended
in Ham’s F-12 with a nd without light irradiation [21].
Figure 5. Mutation frequencies at the hgprt locus in CHO
cells induced by 0%, 0.00001%, and 0.0001% RB sus-
pended in H am’s F-12 with and without light irradiation.
Figure 6. Fluor esce nce int ensity of 1O2 measur ed by Se nsor
Green Reagent : RB suspended in PBS.
Figure 7. Fluor esce nce int ensity of 1O2 measur ed by Se nsor
Green Reagent: RB suspe nded in Ha m’s F-12.
differ from one another, but were found to be signif-
icantly higher than the two highest concentrations, 0.01
and 0.1% RB (p < 0.01). 0.1% RB was significantly dif-
ferent from all other concentrations (p < 0.02), with
nearly undetectable levels of 1O2 species.
2) PBS, 200 Seconds of Light
Controls had significantly lower amounts of 1O2 pro-
duction when compared all other concentrations (p <
0.01), except for the highest concentration, 0.1% RB.
Singlet oxygen production for controls and 0.1% RB
remained quite low, whereas from 0% to 0.001% RB the
levels of 1O2 increased. Levels of 1O2 production were
greatly reduced from 0.001% to 0.01% RB.
Is the Photosuturing Agent, Rose Bengal, a Mutagen ?
3) PBS, 400 Seconds of Light
Controls had significantly lower amounts of 1O2 pro-
duction from all other concentrations (p < 0.01), except
for the two highest concentrations, 0.01% and 0.1% RB.
Levels of 1O2 production increased from 0% to 0.001%
RB, but there was a decrease in 1O2 production between
0.001% and 0.1% RB.
3.3.2. Sensor Green Assay in Ha m’s F-12 Medium
1) F-12, No Light
Similar findings as in the PBS, “No Light” group
above were discovered. 0.1% RB concentration was sig-
nificantly different from all groups (p < 0.02), with near-
ly undetectable levels of 1O2 molecules.
2) F-12, 200 Seconds of Light
Controls produced low levels of 1O2 species, and were
not significantly different from 0.00001% or 0.1% RB.
Most of the remaining concentrations significantly dif-
fered from one another (p < 0.01), with increased 1O2
production from 0% to 0.001% RB, and decreased de-
tectable 1O2 from 0.001% to 0.1% RB.
3) F-12, 400 Seconds of Light
There was an increase in 1O2 production from 0% to
0.001% RB, and reduced detection of 1O2 levels from
0.001% to 0.1% RB. Controls produced low amounts of
1O2 and were not statistically different from 0.1% RB,
but were significantly different from all other concentra-
tions (p < 0.01). All other concentrations were signifi-
cantly different from one another (p < 0.01).
4. Discussion
Finding improved wound closure techniques with few
side effects is an important topic [22-24]. RB has only
recently been investigated as a PTB agent [1,2,7]. It was
initially thought to be harmless and unable to penetrate
vital cellular o r ganelles, however, studies show RB stains
nuclei and other e ssential organelles, i.e., in huma n inte s-
tine smooth muscle cells (HISM) [18]. Additionally,
photoactivated RB generates ROS and has been used to
induce strokes in mice [17,25]. ROS are important for
many normal physiological processes, but high levels
cause DNA and cell membrane damage, which can be
cytot oxic. S tudie s have i nvest igated RB’s RO S induct ion,
cytotoxicity, staining of cellular organelles, and histo-
logical and macroscopic outcomes of PTB, but few ad-
dress the issue of photoactivated RB-induced mutagenic-
ity [3]. Both UVA and chemical- or photochemically-
induced formation of 1O2 exhibit the ability to modulate
gene expression, enzyme induction (i.e., collagenases,
and intercellular adhesion molecule-1) [26]. Chemical- or
photochemically-induced formation of 1O2 appears to
have effects si milar to those o f UVA radiation, incl uding
activation of c-Jun amino-terminal kinases (JNK) in hu-
man skin fibroblasts [15]. 1O2 has been implicated in al-
tered dermal states arising from abnormal collagen cross-
linking from 1O2 targeting histidine and histidinohydrox-
ylsino no r le uc ine via p ho to o xid a tio n i n bo vine sk in wh ic h
may reduce tensile properties [27].
Reducing incubation from 5 minutes to seconds, there
is rapid dye uptake by stained cell membranes and nuc-
leus in HISM cells with 0.1% RB. Cells incubated for
longer periods of time have reduced intracellular fluo-
rescence emission, likely a result of the dye’s self-
quenching effect. Regarding RB’s intrinsic toxicity,
morphologic changes were exhibited in four cell types
(rabbit tendon fibroblasts, cells from bovine pulmonary
artery, HISM, and rabbit corneal epithelial cells) in the
presence of varying concentrations in the dark and am-
bient lighting, where higher (1%) concentrations of RB
appear to cause cell detachment and loss, and lower (e.g.,
0.01%) concentrations reduce cellular motility [18].
With the above information in mind, this study was
designed to test the hypothesis that photoactivated RB
induce s RO S (name ly 1O2) at low concentrations reduces
cell viability and increa ses genotoxicit y in epithelial cells.
The range of RB concentrations selected increased from
0 to 0.1% RB (concentration recently investigated in
human subjects) [1,2,7]. Light irradiation exposure time s
included 0, 200, and 400 seconds (double the length of
time in recent research) to compensate for the lack of a
source of concentrated green wavelength. Having piloted
a study where cultures exposed to 0% and 0.1% RB in
PBS, PBS was itself cytotoxic within 24 hours. As a re-
sult, we suspended RB in Ham’s F-12, as this was not
overtly detrimental to viability. Green light minimally
penetrates the epidermis in animal models, which should
thereby localize photodynamic therapies to the epidermis
[28]. We irradiated cells with a high intensity light
source, containing green wavelengths, and is also mini-
mally penetrating [1 5].
RB concentrations >0.001% in Ham’s F-12 were very
cytotoxic. The XTT assay revealed that viabilities were
uninfluenced by low RB concentrations (i.e., ≤0.0001%
RB) maintai ned in the d ar k, or a fter 30 min of inc uba tion .
These values are quite low compared to concentrations
used in recent human research (i.e., 0.1% RB) [2,7].
Perhaps at RB concentrations as low as 0.0001%, there is
not enough 1O2 production to exhaust the cells’ innate
ability to overcome the detrimental effects of ROS at
these low concentrations. Time appears to play a role in
the effect on viabilit y, with 49% of irradiated cells being
lost after 24 ho urs of incubati on in co ncentr atio ns as l ow
as 0.0001% RB. This is possibly due to an increased
amount of time the cells were exposed to oxidative stress
and the associated detrimental effects. At ≥0.001% RB,
the effects were even more obvious with >90% of cells
being lost. This supports a dose-dependent negative ef-
fect on viability and a possible interaction with light and
time at the lowest concentration out to 24 hours. Again,
Is the Photosuturing Agent, Rose Bengal, a Mutagen?
the resulting cytotoxicity from these low RB concentra-
tions (e.g., 0.001%) is well below the 0.1% conce ntratio n
used in clinical studies.
The Sensor Green reagent revealed that irradiating
0.00001% - 0.001% RB increased amounts of detectable
1O2 species, with a significant reduction between 0.01% -
0.1%. While an increase in 1O2 production with increas-
ing RB concentrations seems relatively intuitive, the data
concerning 0.01% - 0.1% RB concentrations were unex-
pected. Perhaps this observation can be explained by
photoactivated RB’s ability to undergo auto-exhaustion
during shorter periods compared to lower concentrations.
Assessing 1O2 production at varying time points might be
a way to investigate these observations. Alternatively,
perhaps higher concentrations of RB absorb or mask
Sensor Green’s fluorescence as these concentrations are
much mo re hea vil y pig mented than lower c once ntratio ns.
As expected, controls exhibited almost no 1O2 produc-
The initial HPRT gene mutation assay showed that ir-
radiating ce lls with 0. 000 1% RB in Ha m’s F -12 was pos-
sibly mutagenic, with roughly a doubling of the mutant
frequency above background. However, results from the
second experiment using lower RB concentrations sug-
gested that RB was not mutagenic at 0.0001% or
0.00001% concentr ations . This is no t unrea sonabl e since
the highest co ncentratio n is quite lo w (~1 uM). All ot her
concentrations resulted in low or nonexistent colony
formation due to RB’s cytotoxicity. Qualitatively, when
comparing the HPRT groups to controls (colony forming
plates), which were elevated beyond expected, there were
no apparent differences in freq uency of H PRT mutations
amongst experimental groups. In our opinion, the assay
did not meet the quality standard s that we set, and several
experiments could be repeated. Investigating the muta-
genicity of photoactivated RB on skin cell lines should
also be considered.
5. Conclusion
With the current information at hand, it appears that
higher concentrations of RB on viable cells are relatively
cytotoxic. Singlet oxygen production increased from 0 to
0.001% RB, with detectable levels decreasing from
0.001% to 0.1% RB for unknown reasons. Further re-
search might include a shorter time period between pho-
toactivation and microplate fluorometry to rule out the
auto-exhaustion theory, as well as different time points
between exposure and ROS measurement. Given that
photoactivated RB is currently being tested as a PTB
agent on open wounds, additional research on the poten-
tial mutagenicity of RB needs to be done. Should RB
prove not to be mutagenic, future research might focus
on determining the exact mechanisms and/or effects of
PTB on wound healing a nd scar fo rmation. Perhap s PTB
has potent ial to reduc e infectio n, additional post-operative
pain, and poor cosmetic outcomes. Of note, photoacti-
vated RB has recently shown promise as a fungicidal
agent agai ns t Trichophyton rubrum [29]. Other ite ms that
should be considered include the potential for an in-
creased risk of future complications, such as localized
pigment di s orders or even skin malig nancies.
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