1. No category

j. Cosmet.
Sci., 50, 327-339 (November/December
1999)
Effectof coconutoil on preventionof hair damage. Part I
AARTI S. RELE and R. B. MOHILE, Research
& Development
Department,
NatureCareDivision,MaricoIndustries
Ltd., Andheri,
Mumbai 400 058, India
Accepted
for publication
September
30, 1999.
Synopsis
Beneficialeffectsof coconutoil on preventionof combingdamageon differenttypesof hair havebeen
established
by proteinlossand water retentionmeasurements.
In vivo,salon-based,
half-headtestsconfirm
thesebeneficialeffects.Beneficialeffectswere alsoobservedon chemically(bleached)and thermally (treated
with boilingwater)damagedhair. In additionto providinglubricatingfilm, it is hypothesized
that coconut
oil usedasa prewashpenetratesendocuticularmaterial in the intercuticularregionand reducesits swelling
propensity.The penetrationof waterinto the intercuticularregionis preventedby hydrophobic
oil film at
the edgeof the cuticle.Both theseeffectspreventthe lifting of the surfacecuticleand its breakingby the
forceexertedby the comb.
INTRODUCTION
Hair fibersconsistof threedistinctmorphologicalcomponents,
namely,the cuticle,the
cortex,and the medulla.Layersof cuticlecellsform the outersheathof the fiber and are
mainly responsible
for the cosmeticpropertiesof hair. Mechanicalproperties,on the
other hand, are attributed to the cortex, which forms the bulk of the fiber.
Becauseof extensivecross-linking,cuticle cells tend to be brittle and, therefore,are
susceptible
to damageby groomingprocedures,
especially
wet combing(1). The lossof
cuticlecellsby gradualchippingimpairsthe structuralintegrity of hair, leadingultimatelyto split endsand fracture.This limits the lengthand the cosmeticqualitiesof
hair suchassmoothness
and shine.Groomingmethodsinvolvingabrasiveprocedures
are
known to damagehair and its appearance.
Historically,coconutoil hasbeenusedasa hair dressingin the developingcountriesin
the tropicalregionsof the globewherecoconutis cultivatedextensively.Prolongeduse
of coconutoil hasbeenknown to lead to healthy-lookinglong hair, suggestingthat it
maypreventdamageto the cuticlein groomingprocedures
involvingabrasion.Obvious
is the lubricatingeffectof oil on fiberfriction,whichreduces
abrasivedamage,especially
in combing.
This investigation
is aimedat presentingalternativemechanisms
for the beneficialeffect
of coconutoil in preventinghair damagewhen usedas a preconditioner.Although
327
328
JOURNAL OF COSMETIC SCIENCE
severalmethodsinvolving scanningelectronmicroscopy(SEM) and measurementof
combingforcesand tensilemechanicalpropertieshavebeenusedearlierto characterize
hair damage,we haveusedproteinlossand wateruptakemethodsfor this purpose(3).
We havealsousedconsumer-perceived
attributesof hair qualityasadditionalmeasures
of hair damageand its alleviation.Furthermore,thesemethodshave beenextendedto
studythe beneficialeffectsof coconutoil on chemicallytreated(bleached)hair and hair
treatedwith boilingwaterfor 2 hr. Thereis a largeamountof work showingthis effect.
It is well knownthat bleachedhair, because
of its high degreeof swelling,is moreprone
to groomingdamage,especiallyin the wet condition(2).
MATERIALS
AND
METHODS
MATERIALS
Samplesof straight,curly,and wavyhair of Indian originwereusedin this work along
with a sampleof untreateddark brownhair from DeMeo Brothers,New York. The
lengthsof the Indian and DeMeo hair strandswere 25 and 15 cm, respectively.The
reagentsfor protein estimationwere obtainedfrom SigmaChemicalsCo. (St. Louis,
MO). All other reagentswere of analyticalgrade.
Sample
Preparation.
Hair tresses
of 3 + 0.5 g (or 2 + 0.2 g for DeMeohair)wereprepared
for this investigation.They werecleanedby soakingin 0.01% (w/v) of polysorbate
80
(30 rain at 28øC), de-ionizedwater at room temperature(severalrinses),and 0.01%
(w/v) aceticacid (15 rain at 28øC), in that order. Finally, they were extensivelyrinsed
in water and blow-dried.
Bleachedhair was preparedby using a bleachingkit containing30 vol. hydrogen
peroxideandammoniasolutionto adjustthe pH to -10. Fivemillilitersof this solution
wasemployedper tress,and the treatmenttime was 120 min. With this treatmentthe
tressesbecamelight brown with a red tone.
The boiling watertreatmentwascarriedout for 120 min. After bleachingor boiling in
water, someof the tresseswere treatedwith 0.2 ml of coconutoil, spreaduniformly
throughoutthe tressby a brush.The tresses
werestoredat roomtemperature
for 48 hr
before use.
The entirestudyinvolvedsampleswith the followingtreatmentson four typesof hair,
i.e., DeMeo and Indian (straight,curly, and wavy):(a) undamagedcontrol;(b) undamaged/coconut
oil; (c) bleached;(d) coconutoil/bleached*;(e) bleached/coconut
oil*; (f)
boiling water; (g) coconutoil/boiling water*; and (h) boiling water/coconutoil*.
Twenty-fivereplicatetresseswere usedfor eachtreatment.
METHODS
The tresseswere wet under running tap water (28øC) and were washedwith a 20%
Sequentialtreatments.
HAIR
DAMAGE
PREVENTION
BY COCONUT
OIL
329
solution of sodium laureth (3 moles of EO) sulfate (SLES). One milliliter of the solution
wasappliedper tressand the tresseswereworkedbetweenfingersto producea lather.
Followingthis, they were extensivelyrinsedto removeall the SLESresidues.After this
treatmentthe tresseswere subjectedto the following investigations.
Combing
damage.
The protein-lossmethod of Sandhuand Robbins(3) was usedin the
following manner: Each of the wet tresseswas combed with a fine-toothed nylon
comb (20-22 teeth/inch) 50 times, rather vigorously,along the entire length of the
tresson both sides.After everyfive strokesthe comb was dipped in 50 ml of water
containedin a beakerto dislodgethe debris. The entire tresswas dipped in water
after every ten strokesto collect the damagedand dislodgedcuticle cells. The
water suspension
wastestedfor protein contentusing the Lowry method.This method
involvesthe formationof a copper-proteincomplexin alkaline solutionthat in turn
reactswith phosphomolybdic-phosphotungstate
reagent (Folin-Ciocaltaeuphenol reagent) to yield an intenseblue-coloredsolution, which is analyzedspectrophotometrically.
Water-retention
index(WRI). The SLES-washed
tresswas weighedand then soakedin a
0.01% solution of polysorbate80 for 30 min. Following this procedure,the tresswas
centrifugedto removecapillarywaterandthenweighed.In the nextstep,the dry weight
of the hair wasdeterminedby drying the tressin a vacuumovenat 50øC for 90 min and
then weighingit again.The water retentionindex (WRI) is given by:
WRI = (Wwe
t - Wdry)100/Wdry
Evaluationof cosmetic
attributes.
These evaluationswere made on normal untreated and
bleached hair, with and without coconut oil. For each treatment three tresseswere
treated with
0.2 ml of coconut oil and the other three were used as untreated
controls.
The attributesevaluatedin this studywere easeof combing(wet and dry), smoothness,
bounce,setting,luster,and flyaway.All the attributeswereratedon a scaleof 1-5 (1 is
poor and 5 is excellent).Three judgesdid the ranking.
Half-headtests.Eachhalf-headtest involved20 clients,eachwith normal and bleached
hair. The hair wasparted in the middle, and half the headwastreatedwith coconutoil
and the other half was left without
treatment.
Then the hair was washed with
warm
water (28øC, 200 ppm hardness)
using 20% SLESand rinsedwell to removeany residue.
To avoid inherent differencesin damagefrom left to right side, application of the
treatment was randomized. Panelistswith an odd number were treated on the left side,
while thosewith an evennumberwere treated on the right side.
After shampooing
and rinsing,the hair wascombedwith a fine-toothedcomb(separate
combfor eachside).After eachof the ten combingstrokes,both the hair and the comb
weredippedin 200 ml of waterto recoverbrokencuticledebris.A total of 100 strokes
(50 on eachside)wasapplied.The suspension
with cuticle debriswasusedfor protein
estimation.
The entire study was carriedout accordingto a completelyrandomizedblock design
approach,and the outcomeof theseexperiments
wasanalyzedstatistically(taking into
accountthe meanstandarddeviationof the numberof replicates)for the significance
of
the treatment
effects within
the confidence limits.
330
RESULTS
PROTEIN
JOURNAL OF COSMETIC SCIENCE
AND
DISCUSSION
LOSS
This is the mostimportantmeasurement
relevantto hair damage.It is well known that
wet combingis accompaniedby the breakingof the surfacecuticle cell becauseof its
brittleness.Histologically, the major componentof the cuticle cell consistsof the
exocuticleand the endocuticleas shown in Figure 1. The exocuticle,being highly
cross-linked,is not swollenby water. The endocuticleand the cell membranecomplex,
on the other hand, are lesscrosslinkedand are more vulnerableto damage.This leadsto
the lifting of the surfacecuticlevia bending.Suchcuticlecellscan be brokenin the
processof combingor teasing.The protein lossobservedin thesemeasurements
results
mostlyfrom the cuticularregion.Because
of the shorttime involvedin the combingand
brief immersionof the combtressin water, it is unlikely that proteinsfrom the bulk of
the fiber are involved in this measurement.
The data for protein-lossmeasurementfor undamagedhair are shown in Figure 2.
Forc•
Crack
Swollen endocuticle
Figure 1. Schematic
diagramof the possiblemechanism
ofchippingof surfacecuticlecellsin wet combing.
HAIR
DAMAGE
PREVENTION
BY COCONUT
OIL
331
zoo
366,67
350
321.73
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30& .7
,
300
26/-,.07
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2 50
200
160.66
•5o
100
136,6
g
so
DeMeo
Strctight
Wavy
Curly
HAl R TYPES
With Coconut
Oil
[] WithoutCoconut
Oil
Figure 2. Comparisonof proteinlossin wet combingfor undamagedhair.
Clearly,the proteinlossis significantlyreducedby the applicationof coconutoil as a
prewashconditioner(coconutoil appliedbeforeSLESwash).The sametrend is also
observed
in the caseof bleachedhair and hair treatedwith boilingwater (Figures3,4).
•.•700
622.75
600
500
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Straight
Wavy
Curly
300
200
•00
0
HAIR
TYPES
I[•Without
Coconut
Oil
r•With
Coconut
Oil
as
Postwash
r']With
Coconut
Oil
as
Prewosh
]
Figure 3. Proteinlossin wet combingof bleached
hairwith coconutoil aspre-andpostwash
conditioner.
332
JOURNAL OF COSMETIC SCIENCE
450
396.65
$386,26
aO0
350
300
231.03
•5o
200
150
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loo
•
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o
303,82
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• 175.46
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DeMeo
Straight
HAIR
Wavy
Curly
TYPES
Jl•Jwithout
Coconut
OilJ•J
With
Coconut
Oil
asPostwash
J--J
With
Coconut
Oil
asPrewash
J
Figure •. Proteinlossfrom hair treatedwith boilingwaterand the ef[bctof coconutoil asa conditioner.
With thesetwo damagedsamples,coconutoil wasalsousedasa postwashconditioner
(coconutoil after SLESwash)in additionto useasa prewashtreatment.The difference
betweenthe resultsof the prewashandpostwashtreatmentsreflectsthe relativeimportanceof fiber lubricationon cuticle loss.From the point of view of combingdamage,
limiting the swellingof the fiber appearsto be morebeneficialthanjust lubricatingthe
swollen fiber.
As in the laboratorytest, the beneficialeffectof coconutoil wasalsoobservedin a salon
test.A significantdifferencein proteinlosswasobserved
with (13.1 pg/g) and without
(203.02 pg/g) coconutoil for normalhair. For bleachedhair, the corresponding
values
were304.8 and 466.0 pg/g, respectively,
for treatmentswith and without coconutoil.
The beneficialeffectof coconutoil in preventingcuticledamagein the laboratorytest
was established
statisticallyby analysisof variance(ANOVA). The outcomeof the
analysis
is shownin TableI. F-valuesclearlyindicatethat damagedaswell asundamaged
hair benefit from applicationof coconutoil as a prewashconditioner.The effectsof
coconutoil werealsopositivein the salontest,ascanbe seenfrom the datain TableII.
In both normal and bleachedhair, treatmenteffectsin reducingprotein lossare significant.
This is alsoseenin pair-wisecomparison
usingthe t-test.The datais shownin TableIII.
In this table, there are four outcomesthat are not statisticallysignificant.They are
comparisons
of hair treatedwith boilingwaterfor 2 hr (withoutanytreatment)with hair
treatedwith coconutoil after treatingwith boiling water for 2 hr. This clearlyshows
that the cuticledamagehasoccurredin the hair treatedwith boiling water for 2 hr
beforethe applicationof coconutoil.
HAIR
DAMAGE
PREVENTION
Table
BY COCONUT
OIL
333
I
Analysisof Variancefor TreatmentEffects
Hair type
DeMeo
Straight
Wavy
Curly
Sourceof variance
Degreesof freedom*
Between treatments
Sumof squares Mean square
7
Experimentalerror
Betweentreatments
Experimentalerror
Betweentreatments
Experimentalerror
Betweentreatments
Experimentalerror
3545687.30
192
7
192
7
192
7
192
620411.57
35050625.20
2543128.50
3071240.99
2967233.28
2729734.30
3429503.00
506526.76
3231.31
500723.60
13245.46
438748.71
15454.34
389962.04
17861.99
F-Value
156.76
37.80
28.39
21.839
* F theoreticalfor degreesof freedom(7,192) at 95% confidencelevel = 2.01.
Table
II
Analysisof Variancefor Half-Head Treatmentsand Their Significance
Hair type
Normal
Bleached
Sourceof variance
Degreesof freedom*
Between treatments
1
Experimentalerror
38
Between treatments
1
Experimentalerror
38
Sumof squares Mean square
51724.87
4751.07
259854.40
15077.94
51724.87
F-Value
413.70
125.03
259854.40
654.89
396.79
* F theoreticalfor degreesof freedom(1,38) at 95% confidencelevel = 4.08.
Table
III
Pair-Wise Comparisonof TreatmentEffects*
Treatment
DeMeo
Straight
Wavy
Curly
Undamaged:with and without coconutoil
Undamaged:without coconutoil and bleached
Undamaged:without coconutoil and boiled
Bleachedand treatedwith boiling water
6.55
17.55
5.21
16.02
1.73
2.35
4.59
7.43
8.26
26.24
32.99
2.26
5.26
9.63
1.83
10.00
Coconut oil-treated; bleachedand coconut
32.07
13.16
4.93
16.88
10.28
8.85
17.04
7.04
6.33
0.06
0.91
0.81
1.51
1.91
1.70
1.26
6.91
13.22
3.85
3.91
7.29
8.63
1.82
3.47
oil-treated;treatedwith boiling water
Bleached; coconut oil-treated and treated
with boiling water; coconutoil-treated
Treated with boiling water and coconut
oil-treated;treatedwith boiling water
Treated with boiling water and treated
with boiling water; coconutoil-treated
Bleachedand coconutoil-treated; bleached
Bleached and bleached; coconut oil-treated
* Student'st-test theoreticalfor 48 degreesof freedomat 95% confidence
level = 1.645.
Protein-lossmeasurements
werealsousedto highlight the beneficialeffectof coconutoil
as a prewashconditionerfor different commercialshampoos(insteadof 20% SLES).
Sevendifferentbrandswereusedin this studyinvolvingIndiancurlyandstraighthair.
Protein-loss
datain Figures5 and6 onceagainshowthat combingdamageis alleviated
by coconutoil usedasa conditioner.Curly hair showsa greatertrend towardsprotein
334
JOURNAL OF COSMETIC SCIENCE
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366-67
4
5
SHAMPOO
BRANDS
WithoutCoconut
Oil
•
6
7
[•'•Jwith
Coconut
Oil as Prcwash
Figure 5. Reductionof proteinlossby prewashtreatmentwith coconutoil on curlyhair washedwith
variouscommercialshampoos.
350•
30 4.7
300
264,1
250
209,56
194,25
200
153.27
150
100
50
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2
3
4
5
SHAMPOO
BRANDS
6
7
With
Coconut
Oil [] With
Coconut
Oil
cts
Prewash
I
Figure 6. Reductionof proteinlossby prewash
treatmentwith coconutoil on straighthairwashed
with
variouscommercialshampoos.
HAIR
DAMAGE
PREVENTION
BY COCONUT
OIL
335
lossascompared
to straighthair.This is mainlydueto greatercomb-hairinteractions
of a frictionalnaturein curly hair as comparedto straighthair.
WATER-RETENTION
INDEX
The water-retentionindexof undamagedhair is shownin Figure7. From the data it can
be seenthat coconutoil reducesthe WRI by 2-5%. Sincecoconutoil was usedas a
prewash
conditioner,
it wouldbereasonable
to conclude
thatthe effectmaybe dueto
oil residues left in the hair.
The datafor the bleachedand boiling-water-damaged
hair are shownin Figures8 and
9, respectively.
Forthesedamaged
samples,
theWRI is muchhigherthanthatfor the
undamaged
hair. This is mostlydue to chemicaldegradation
of proteins,generating
hydrophilic
groups.Bothcleavage
andoxidationof disulfidebonds,aswellashydrolysis
of thepeptidelinkage,occur,althoughthecontribution
of thelatteris probablyminor.
All samples
showa reduction
in theWRI asa resultof theapplication
of coconut
oil.
Assuming
that mostof thewateris absorbed
by thefiber,theWRI reflectsthe swelling
propensity
of hair.Sincerepeated
swellingandcontraction
damage
thecuticle,reduction
in the WRI can be consideredas beneficialin reducinghair damage.
The data in Figures8 and 9 showthat the sequence
of application(whetherpre- or
postwash)
is important.Postwash
applicationis lesseffectivein reducingthe WRI as
compared
to prewash
application.
The difference
seems
to be in the locationof the oil
residues.
In postwash
application
the oil film is on the surface,
with nopenetration
into
thefiber.In prewash
application,
because
thefiberis swollenaftertheapplication
of the
1'6
14.10
12.10
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9.02
ß
8.42
2
o
De M½o
S trmght
HAIR
Wavy
Curly
TYPES
r--IWith
Coconut
Oil•,•Without
Coconut
OilJ
Figure 7. WRI of varioushairtypes:Effectof coconut
oil asa prewash
conditioner.
336
X
JOURNAL OF COSMETIC SCIENCE
60
••
38.02
•
31.6
2
• 20,00
27.23
•
1'9,68
20.19
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z
LI.I
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•0
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DaMco
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Wavy
HAIR
Curly
TYPES
W(thout
Coconut
Oil [•'lWith
Coconut
OilasPostwash
['-IWithCoconut
OilasPrcwash
Figure8. WRI of bleached
hairwithcoconut
oil asa pre-andpostwash
conditioner.
x
80
74,•4
70
64.92
61.07
57,19
60
50
52,35
,55•j
53.59
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ß
5trai cjht
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C u rl y
49,15
39,12
40
30
20
10
0
DeM½o
HAIR
TYPES
[]Without
Coconut
OilE•]With
Coconut
Oil
asPostwash
[--IWith
Coconut
Oil
as
Prcwash
I
Figure9. WRI ofboiling-water-damaged
hairwithcoconut
oil asa pre-andpostwash
conditioner.
oil,it is possible
thatthemolecules
oftheoil penetrate
intothecuticle
andprobably
eventhecortex.
Thismayalsobethecasewith undamaged
hair,although
theeffectis
small.The reductionin the WRI must be due to the introductionof the hydrophobic
triglycerideinto the keratinstructure.
HAIR
BENEFITS
ON
COSMETIC
DAMAGE
PREVENTION
BY COCONUT
OIL
337
ATTRIBUTES
This studywasconductedin vitroon undamagedand bleachedhair usingcoconutoil as
a prewashconditioner.Three judgesrankedthe cosmeticattributes,which havebeen
listedearlier.The rankingsareshownin Figures10 and 1l, respectively,
for undamaged
and bleached hair. The beneficial effects of coconut oil are seen for most of the cosmetic
attributes
MECHANISM
of hair.
OF PROTECTION
BY COCONUT
OIL
The histologyof a cuticlecell and the mechanismof damagein wet combingproposed
by Swift(4,5) is shownin Figure1. Because
of cross-linking,
the exocuticleis brittle and
doesnot swell. The endocuticleand the cell membranecomplexhavelesscross-linking
and thereforeswellsignificantly.This effectproducesthe tendencyfor the surfacecuticle
cellsto curveupwardand breakwhen pressureis appliedwith a comb.
Recentstudiesof Ruetschand Weigmann(6) confirmthat the endocuticleand the cell
membranecomplex(CMC) are the loci of weaknessand that fractureoccurswhen the
fiber is extended.Chemicalmethodsweakenthe adhesionof the cell membranecomplex
betweenthe cuticlecells.The degreeof swellingof the cuticularlayersis increasedby
disulfidecleavageand oxidation.This enhances
the combingdamageand protein loss,
especiallyin wet combing,as observedin this study.
Coconutoil is mostly a triglycerideof lauric acid and hydrophobic.Application of
coconutoil asa prewashconditionercoatsthe hair and inhibits the penetrationof water
into the hair. A smallpart of it is alsoabsorbedinto the hair during the washwhen the
5
4.5
4.5
4
1
2
5
5 4.5
•
3
5
5
6.5
4
4
4,5
4
5
6
7
ATTRIBUTES
WithoutCoconut
Oil
r•With
Coconut
Oil
Figure 10. Effect of coconutoil on cosmeticattributesof normal hair (i. vitropanel test).
338
JOURNAL OF COSMETIC SCIENCE
5
4.5
4.5
5
• 4.5
/
3
1
3
2
•
//
3
5
•
4,5
3ø5
3
4
5
4.5
3
5
6
7
%
ATTRIBUTES
WithoutCoconut
Oil
[]With
Coconut
Oil
us
Prcwush
I
Figure 11. Effectof coconutoil on cosmeticattributesof bleachedhair (in vitropaneltest):Protectiveeffect
in improving appearance,
fiber is swollen.Introduction of this hydrophobiccomponentreducesthe swelling
propensityof the cuticle, which limits the upward curving of the surfacecuticle.This
reducesthe chippingawayof the cuticlecells,which reducesproteinloss,asobservedin
this work.
Becauseof its low molecularweight (-1000) the oil may alsopenetratethe cortex.Once
again,because
of the introductionof hydrophobicfunctionalityinto the fiber, the WRI
is reduced.Reductionof water absorptionand associated
swelling seemsto be the
dominantmechanismof protectionfrom the coconutoil. Lubricationprovidesan additional level of protectionin groomingprocesses.
CONCLUSIONS
This studyhasfirmly established
the protectiveeffectof coconutoil on hair damagein
groomingprocesses
whenit is usedasprewashconditioner.It alsohasa protectiveeffect
on chemicallytreated hair and hair treated with boiling water (i.e., hair in water at
100øCfor 2 hr). The hydrophobicity
of coconutoil seemsto be responsible
for thiseffect.
Coatedon the fibersurface,it canpreventor reducethe amountof waterpenetratinginto
the fiber and reducethe swelling.This in turn reducesthe lifting of the surfacecuticle
andpreventsit from beingchippedawayduring wet combing.A reductionin the WRI
is additionalevidencefor the decrease
in water absorption.In additionto its protective
effect, coconutoil seemsto improve a number of cosmeticattributes of hair. Other
benefitsof this naturalprewashhair conditionerare underinvestigation.
ACKNOWLEDGMENT
The authors would like to thank Dr. Yash Kamath, Director of Research,T.R.I.,
Princeton,New Jersey,for his valuableguidancein writing this paper.
HAIR
DAMAGE
PREVENTION
BY COCONUT
OIL
339
REFERENCES
(1) M.L. Garcia and J. Diaz, Combability measurements
on human hair, J. Soc.Cosmet.
Chem.,27,
379-398 (1976).
(2) L.J. Wolfram, J. Soc.Cosmet.
Chem.,21,875 (1970).
(3) S.S. Sandhuand C. Robbins,A simpleand sensitivetechnique,basedon protein lossmeasurement,
to assess
surfacedamageto humanhair,J. Soc.Cosmet.
Chem.,44, 163-175 (1993).
(4) J. A. Swift and A. C. Brown, The critical determinationof fine changesin the surfacearchitectureof
humanhair due to cosmetictreatments.
J. Soc.Cosmet.
Chem.,23, 695-702 (1972).
(5) J. A. Swift, Int. J. Cosmet.
Sci., 13, 143 (1991).
(6) S. B. Ruetschand H. D. Weigmann,J. Soc.Cosmet.
Chem.,47, 13-26 (1996).