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ORIGINAL
ARTICLE
Elevated formaldehyde concentration in ‘‘Brazilian
keratin type’’ hair-straightening products:
A cross-sectional study
Mbulelo H. Maneli, PhD,a Peter Smith, PhD,b and Nonhlanhla P. Khumalo, FCDerm, PhDa
Cape Town, South Africa
Background: Brazilian keratin treatment (BKT) and similar straightening products fix and retain a straight
shape even when the hair is wet. Unacceptably high concentrations of formaldehyde have been reported in
such products.
Objective: We sought to measure the formaldehyde concentration in all BKT brands marketed in South
Africa in 2012.
Methods: We quantified formaldehyde by high-performance liquid chromatography with ultraviolet light
detection after derivatization with dinitrophenylhydrazine. All components of 7 identified commercial
brands were each tested 3 times.
Results: The maximum safe concentration of formaldehyde set by the US Cosmetic Ingredient Review
Expert Panel is less than 0.2%. Of the 7 commercial BKT brands, 6 had formaldehyde levels that ranged
from 0.96% to 1.4%, ie, 5 times higher than the recommended level; these included 5 brands labeled
formaldehyde-free.
Limitations: The study is limited by not including all internationally available BKT products.
Conclusions: Formaldehyde concentrations in BKT products may exceed recommended levels and serve
as a health hazard. Industry monitoring is needed to improve compliance and protection of hairdressers
and consumers. ( J Am Acad Dermatol 10.1016/j.jaad.2013.10.023.)
Key words: Brazilian keratin treatments; formaldehyde; hair; hairdressing; public health.
H
eat straightens hair by breaking down
temporary hydrogen bonds found between
keratin filaments, but the effect is lost when
the hair gets wet. A Brazilian mortician is said to have
invented a method where keratin fibers in heatstraightened hair are cross-linked to retain a straight,
water-resistant shape for up to 3 months. The convenience and popularity of long-lasting straight hair
has resulted in a flood of products. These brands are
known by various names.1
Brazilian keratin treatments (BKT) and similar
products internationally and in the United States
have been reported to contain unacceptably high
From the Division of Dermatologya and Division of Pharmacology,b Groote Schuur Hospital, University of Cape Town.
Supported by the National Research Foundation (South Africa).
Conflicts of interest: None declared.
Accepted for publication October 11, 2013.
Reprint requests: Nonhlanhla P. Khumalo, FCDerm, PhD,
Division of Dermatology, Ward G23, Groote Schuur Hospital,
Abbreviations used:
BKT:
DNPH:
DNPHF:
HPLC:
Brazilian keratin treatment
dinitrophenylhydrazine
formaldehyde dinitrophenylhydrazone
high-performance liquid
chromatography
levels of formaldehyde.1,2 The Cosmetic Ingredient
Review was established in 1976 by the industry trade
association (now the Personal Care Products
Council), with the support of the US Food and
Drug Administration and the Consumer Federation
University of Cape Town, Observatory 7925, South Africa.
E-mail: [email protected].
Published online December 8, 2013.
0190-9622/$36.00
Ó 2013 by the American Academy of Dermatology, Inc.
http://dx.doi.org/10.1016/j.jaad.2013.10.023
1
J AM ACAD DERMATOL
2 Maneli, Smith, and Khumalo
of America.3 According to the Cosmetic Ingredient
Sampling
Review Expert Panel, formaldehyde is safe to use at a
Samples were stored at ambient temperature
maximum concentration of 0.2% as a preservative in
until formaldehyde measurements, which occurred
consumer products.4 Formaldehyde may cause
within 2 months of delivery. Three samples
respiratory irritation, contact dermatitis, headaches,
(treatment, shampoo, and conditioner) of each
and pregnancy complications.5 Formaldehyde is
brand were analyzed for formaldehyde concentraclassified as a carcinogen; chronic exposure to high
tion. Each sample was tested 3 times and a mean
concentration is associated
and SD calculated for
with respiratory and hemocomparison.
CAPSULE SUMMARY
poietic malignancies.6,7
Methods of formaldehyde
Preparation of 2,4-DNPH
Formaldehyde concentrations of up to
detection in cosmetics are
solutions: Brady reagent
0.2% are recommended for use in
well established and include
The solution of 0.18-mol/
consumer products. High concentrations
microdiffusion
apparatus
L 2,4-DNPH reagents was
increase risks of cancers and of
with fluorescent illuminaprepared following protocol
respiratory and pregnancy abnormalities.
tion, polarography, thinby Ruekberg and Rossini.8 A
Using high-performance liquid
layer
chromatography,
total of 3.0 g of powdered
chromatography; 6 of 7 ‘‘Brazilian keratin
colorimetry that involves
2,4-DNPH was suspended in
type’’ hair brands had formaldehyde
reaction of formaldehyde
20 mL of water and 70 mL of
concentrations of 0.96% to 1.4%. This
with chromotropic acid,
95% ethanol followed by
included 5 brands labeled formaldehyde2,4-dinitrophenylhydrazine
slow addition of 15 mL of
free.
(DNPH) or acetylacetone,
concentrated sulfuric acid at
high-performance
liquid
108C. Dissolution of 2,4Protective clothing is recommended for
chromatography
(HPLC),
DNPH was completed by
occupations with high formaldehyde
and mass spectrometry.
heating
the
resulting
exposure; this is currently not available
Measurement of formalreddish-yellow
solution
until
to hairdressers. Use of these products
dehyde that relies on the
all
2,4-DNPH
particles
has
requires regulatory review and
reaction of formaldehyde
dissolved
or
until
temperamonitoring.
with 2,4-DNPH8 (condensature reached 608C.
tion reaction) to form a stable
complex and quantification by HPLC is most reliDerivatization of formaldehyde in BKT hair
able.8 HPLC is the technique of choice as it permits
care product and extraction
both instrumentation and quantification to be autoA total of 1 g of cosmetic product was suspended in
mated. It is highly specific and has a selective
excess (approximately 6.0 mL) of 0.18 mol/L of
detection limit, in water, of approximately 6 parts
2,4-DNPH. The resulting emulsion, containing a red
per billion. Further, derivative maximum absorbance
or yellow precipitate of the formaldehyde derivative
at wavelength 365 nm greatly reduces interferences.9
or formaldehyde 2,4-dinitrophenylhydrazones (2,4We aimed to determine concentrations of formalDNPHF), was vortexed and left standing at ambient
dehyde in BKT brands sold on the South African
temperature for at least 10 minutes. The 2,4-DNPHF
market by HPLC with ultraviolet detection after
was vigorously extracted into 10.0-mL dichloromethane
derivatization with 2,4-DNPH.
and 2,4-DNPHF was diluted 50 times to 1.0-mL volume
with methanol before HPLC injection.
d
d
d
METHODS
Material
An attempt was made to identify all BKT products
sold in South Africa from catalogs of large retailers and
local World Wide Web sites that advertise hair products.
Samples of identified product were purchased through
the Internet in the first quarter of 2012. Chemistry
reagents 2,4-DNPH, dichloromethane, acetonitrile,
and sulfuric acid were analytical grade, and methanol
was HPLC grade purchased from Merck (Pty) Ltd South
Africa (Modderfontein, South Africa). Formaldehyde
2,4-DNPH standard was obtained from Sigma-Aldrich
South Africa (Aston Manor, South Africa).
HPLC analysis
The HPLC column method by Benassi et al9 was
used on Shimadzu LC 10A instrument series (Tokyo,
Japan). Briefly, 2,4-DNPHF was subjected to flow
through Agilent Eclipse XDB-C18 column (Agilent
Technologies, New Castle, DE), 5 m, 150 3 4.6 mm,
where acetonenitrile and water (60:40, vol/vol), with
a flow rate of 1 mL/min, served as mobile phase. The
volume of sample injected was 20 L and the
absorption wavelength of a detector was set at 365
nm. The signal peak area was used for quantitative
calculation of formaldehyde. The calibration curve,
J AM ACAD DERMATOL
Maneli, Smith, and Khumalo 3
Fig 1. High-performance liquid chromatography of 2,4-dinitrophenylhydrazones (DNPHF)
(2,4-dinitrophenylhydrazine [DNPH] formaldehyde derivative) showing retention times
(x-axis) and concentration for detected signals (y-axis). A, Positive control. Peak detected
with the retention time of 16.0 minutes, which represents 2,4-DNPHF (sample: commercial
2,4-DNPHF). B, Negative control. Very low peak at 16.0-minute retention time reflecting little
(or no) 2,4-DNPHF and high peak at 12.8 minutes reflects excess or unused 2,4-DNPH (sample:
shampoo). C, Positive test result. Peak detected at 16.0-minute retention time represent
2,4-DNPHF (sample: Brazilian keratin treatment, brand B [Table I]).
in the concentration range of 0 to 25 g/mL, was
constructed by plotting 2,4-DNPHF peak area against
its concentrations. The detection and quantitative
limit to the formaldehyde standard solution were
determined to be 3.31 g/L and 10.0 g/L, respectively. The linear regression of y = 81,072x was
obtained with the correlation coefficient very close
to unity (R2 = 0.995). The 2,4-DNPHF peak area
was corrected for any interference found in blank
sample by subtracting the average peak area of the
interference in blanks from the 2,4-DNPHF peak
areas in peaked samples.
J AM ACAD DERMATOL
4 Maneli, Smith, and Khumalo
Table I. Formaldehyde concentration in Brazilian
keratin type hair products
This included 5 brands labeled formaldehyde-free
and 1 labeled formaldehyde less than 0.2%.
BKT
brand
DISCUSSION
A
B
C
D
E
F
G
Formaldehyde
label
Concentration,
mg/mL
Formaldehyde-free
0.27
Formaldehyde-free
0.28
Formaldehyde-free
0.27
0.2% Formaldehyde 0.26
Formaldehyde-free
0.31
None
0.18
Formaldehyde-free 0.055
6
6
6
6
6
6
6
0.018
0.00
0.0047
0.014
0.016
0.014
0.010
Concentration,
%
1.08
1.08
1.11
1.15
0.96
1.40
0.17
6
6
6
6
6
6
6
0.16
0.00
0.094
0.021
0.11
0.51
0.040
Formaldehyde was quantified by high-performance liquid
chromatography with ultraviolet light detection after derivatization
with 2,4-dinitrophenylhydrazine. Formaldehyde concentration was
determined from a calibration curve constructed by plotting the
formaldehyde 2,4-dinitrophenylhydrazone peak area against its
concentrations (Fig 1, C ).
BKT, Brazilian keratin treatment.
Confirmatory tests
Nuclear magnetic resonance and Fourier transformed infrared spectroscopy10 techniques were
used to confirm the presence of formaldehyde in
tested samples before quantification (data available
on request).
RESULTS
HPLC analysis
Free formaldehyde concentration in BKT cosmetics was determined from known concentration
of 2,4-DNPHF. Fig 1, A, shows HPLC chromatogram
of 2,4-DNPHF standard solution. One main peak was
detected at the retention time of 16.0 minutes, which
represents a 2,4-DNPH formaldehyde derivative
(2,4-DNPHF). The peak area of 2,4-DNPHF is used
to construct the standard curve from which the
formaldehyde concentration is calculated.
Cosmetics (eg, shampoos and conditioners) with
low formaldehyde concentration display low peak
for 2,4-DNPHF and high peak for free 2,4-DNPH (Fig
1, B), which indicate lower amount of 2,4-DNPH
required to derivatize formaldehyde; the rest remains in excess. The opposite is true for the
treatment product that contains high formaldehyde
concentration (Fig 1, C ).
Formaldehyde concentrations
Concentration of formaldehyde based on 2,4DNPHF derivatives in shampoos, conditioners, and
one of the treatment products was shown to be less
than 0.2%. Formaldehyde levels detected from BKT
products are tabulated below (Table I). For 6 BKT,
formaldehyde concentration ranged from 0.96% to
1.4%, which is 5 times higher that the concentration
set by the Cosmetic Ingredient Review Expert Panel.
Formaldehyde is ubiquitous in household products; in cosmetics it is used as a preservative at low
concentration (up to 0.2%). It is essentially used in
BKT products as a fixative that cross-links keratin
amino acid side chains retaining the straight shape in
hair. Initial reports of high formaldehyde concentrations preceded a flood of newer brands that claim to
contain low and no formaldehyde. Although concentrations seem lower in newer brands, they are still
more than 1% formaldehyde10; and there are still
reports of high concentration (eg, an average of 8%
was reported in US products advertized as containing no formaldehyde).11
The popularity of BKT products is increasing
worldwide. We tested 7 brands sold in the South
African market at the time of the study. All advertised
as international brands. We have not been able to
confirm that all were imported from Brazil. The
concentration of formaldehyde in the products we
tested confirms recent international data,10 in spite of
much media attention and regulatory concern.
This study has limited generalizability because it
did not including all internationally available BKT
products. However, the false labeling of products
as formaldehyde-free exposes unsuspecting consumers and hairdressers to adverse effects.
Formaldehyde is unstable in its gaseous state
and exists as a liquid (formalin) in cosmetic
products. At high temperatures, such as occurs
when applying BKT products, formaldehyde gas is
released. A recent simulated air-quality study tested
brands (including those labeled formaldehyde-free)
and found them to have ‘‘.concentrations that
meet or exceed occupational exposure limits.’’12 At
high concentrations formaldehyde is listed as a
carcinogen and its use in industries is regulated
under strict air control. This is not the case in most
hairdressing salons where BKT products are used
daily.
Finally, high concentrations of formaldehyde were
found even in products labeled formaldehyde-free.
Unlike pharmaceutical companies, there is no
requirement to produce evidence of rigorous safety
testing before marketing new cosmetics. However,
perhaps it is time that products known to contain (or
to have mechanisms that function through) potentially harmful ingredients should be required to clearly
list concentrations on labels. Random tests could then
be used to monitor and influence industry practice in
the interest of consumer safety and occupational
health. Compliance with and the adequacy of the
J AM ACAD DERMATOL
recommendation that hair salons use air-monitoring
equipment requires evaluation.11 Decisions about
whether to enforce lower concentrations of formaldehyde in products or recommend appropriate
air-flow control and/or protective garments need to
be made by cosmetic regulators.
The authors are grateful to Anwar Jardine, PhD, and
Lutete Khonde, MSc, from the Department of Chemistry
at University of Cape Town for assisting with nuclear
magnetic resonance tests.
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