prevention of hair damage

j, Cosmet. Sci., 54, 175-192 (March/April 2003)

Effect of mineral oil, sunflower oil, and coconutoil on

preventionof hair damage AARTI S. RELE and R. B. MOHILE, Research and Development Department, Nature CareDivision,MaricoIndustries Ltd., MumbaL India.

Accepted for publication April 29, 2002, Synopsis

Previously publishedresultsshowedthat bothin vitroandin vivococonutoil (CNO) treatments prevented combingdamageof varioushair types.Using the samemethodology,an attempt wasmadeto studythe propertiesof mineraloil and sunfloweroil on hair. Mineral oil (MO) wasselectedbecauseit is extensivelyusedin hair oil formulationsin India, becauseit is non-greasy in nature,andbecause it is cheaperthanvegetableoilslike coconutandsunfloweroils.The study wasextendedto sunfloweroil (SFO)because it is the secondmostutilized baseoil in the hair oil industry on accountof its non-freezing propertyandits odorlessness at ambienttemperature. As the aim wasto cover differenttreatments,andtheeffectof thesetreatmentsonvarioushairtypesusingthe aboveoils,the number of experimentsto be conducted wasa veryhigh numberand a techniquetermedasthe TaguchiDesignof Experimentation wasused.The findingsclearlyindicatethe strongimpactthat coconutoil applicationhas to hair as comparedto applicationof both sunflowerand mineraloils.Amongthreeoils, coconutoil was the onlyoil foundto reducethe proteinlossremarkablyfor bothundamaged anddamagedhair whenused as a pre-washand post-washgroomingproduct.Both sunflowerand mineral oils do not help at all in reducingthe protein lossfrom hair.

This differencein resultscould arisefrom the compositionof eachof theseoils. Coconutoil, being a triglycerideof lauricacid(principalfatty acid),hasa high affinityfor hair proteinsand,because of its low molecularweight and straightlinear chain,is able to penetrateinsidethe hair shaft.Mineral oil, being a hydrocarbon, hasno affinityfor proteinsand thereforeis not ableto penetrateand yield betterresults.In the caseof sunfloweroil, althoughit is a triglycerideof linoleicacid,because of its bulky structuredue to the presence of doublebonds,it doesnotpenetratethe fiber,consequently resultingin nofavorable impact on protein loss.

INTRODUCTION

Morphologically,a fully formedhair fiber containsthree and sometimesfour different unitsor structures.At its surface,hair containsa thick protectivecoveringconsistingof layersof fiat overlappingscale-likestructurescalled the cuticle. The cuticle scales surroundthe cortex,which containsa major part of the fiber mass.The cortex,the secondunit, consists of spindle-shaped cellsthat arealignedalongthe fiberaxis.Cortical cellscontainthe fibrousproteinsof hair. Thickerhairsoftencontainoneor moreloosely packedporousregionscalledthe medulla,locatednearthe centerof the fiber. The fourth 175

176

JOURNAL OF COSMETIC SCIENCE

unit is the intercellularcementthat gluesor bindsthe cellstogether,forming the major pathwayfor diffusioninto the fibers. The cuticleconsists of flat overlappingcells(scales).The cuticlecellsareattachedat the proximalend(rootend),and they point towardthe distalend (tip end)of the hair fiber. However,cuticledamageevidencedby brokenscaleedgesthat canusuallybe observed severalcentimetersawayfrom the scalpis causedby weatheringand mechanicaldamage from the effectsof normalgroomingactions,suchascombing,brushing,and shampooing. Because of extensivecross-linking,cuticlecellstend to be brittle and, therefore,are susceptible to damageby groomingprocedures, especiallywet combing(1). In long hair fibers(25 cm or longer),progressive surfacedamagemay be observed. The lossof cuticle cellsby gradualchippingimpairsthe structuralintegrity of hair, leadingultimately to split endsand fracture.This limits the lengthand the cosmeticqualitiesof hair suchas Table

I

Designof ExperimentUsing the TaguchiModel No.

Oils

Hair type

Hair treatment

Oiling sequence

Shampooing

1 2 3 4 5 6 7

CNO SFO MO MO CNO SFO MO

Straight Curly Wavy Permed Straight Curly Wavy

Undamaged Undamaged Undamaged Undamaged Bleached Bleached Bleached

Before Before Before Before Before Before Before

Once Once Twice Twice Once Once Twice

8

MO

Permed

Bleached

Before

Twice

9 10 11

SFO CNO MO

Straight Curly Wavy

Boiled Boiled Boiled

Before Before Before

Twice Twice Once

12

MO

Permed

Boiled

Before

Once

13 14 15

SFO CNO MO

Straight Curly Wavy

UV-treated UV-treated UV-treated

Before Before Before

Twice Twice Once

16

MO

Permed

UV-treated

Before

Once

17 18 19 20 21 22 23

MO MO CNO SFO MO MO CNO

Straight Curly Wavy Permed Straight Curly Wavy

Undamaged Undamaged Undamaged Undamaged Bleached Bleached Bleached

After After After Afier After After After

Once Once Twice Twice Once Once Twice

24

SFO

Permed

Bleached

After

Twice

25 26 27

MO MO SFO

Straight Curly Wavy

Boiled Boiled Boiled

After After Afier

Twice Twice Once

28

CNO

Permed

Boiled

After

Once

29 30 31

MO MO SFO

Straight Curly Wavy

UV-treated UV-treated UV-treated

After After After

Twice Twice Once

32

CNO

Permed

UV-treated

After

Once

Treatmentsweresequential. If the treatmentis designated asCNO-Permed-Boiled-After-Once,it means permedhair wasfirst put in boilingwaterfor 120 min andair dried,and then 0.2 ml of CNO wasapplied to it. This treatmentwascarriedout for all 25 hair tresssamples.Twenty-fivereplicatetresses wereused for each treatment.

EFFECT

OF COCONUT

OIL ON HAIR

Table

DAMAGE

177

II

Analysisof VarianceData for Half-Head Treatmentsfor ProteinLoss Sourceof variance

Hair type Normal

Between

Oil type MO

Experimentalerror

treatments

Degreesof freedom 1 38

Sum of squares

Mean square

F-Value at 95% confidence level

34.8 2234.6

34.8 58.8

o.6

1.1

Bleached

Between

1

42.8

42.8

Oil type MO

Experimentalerror

38

1545.7

40.7

Normal

Between

Experimentalerror

1 38

39.6 1345.6

39.6 35.4

1.1

Oil type SFO Bleached

Between

48.6 1195.6

1.5

Experimentalerror

1 38

48.6

Oil type SFO

1 38

31.6 195.6

31.6 5.1

6.2

1

36.5

36.5

4.9

38

286.5

7.5

treatments

treatments

treatments

Normal

Between

Oil type CNO

Experimentalerror

treatments

Bleached

Between

Oil type CNO

Experimentalerror

treatments

31.5

F theoreticalfor 1.38 degreesof freedomat 95% confidencelevel = 4.08.

smoothness and shine.Groomingmethodsinvolvingabrasiveprocedures are known to damagehair and its appearance.

Historically,coconutoil hasbeenusedasa hair dressingin the developingcountriesin the tropicalregionsof the globewherethe coconutis cultivatedextensively.Prolonged useof coconutoil hasbeenknownto lead to healthylookinglong hair, suggestingthat it may prevent damageto the cuticle in groomingproceduresinvolving abrasion. Obviousis the lubricatingeffectof oil on fiberfriction,whichreduces abrasivedamage, especially in combing.However,in moderntimes,the trendin hair oil formulationsis more towardsthe useof non-stickyoils suchas mineral oil or lessgreasyoils suchas sunfloweroil. This is doneprimarilybecause of costdifferentialsaswell asto overcome theundesirable properties of coconutoil suchasgreasiness, its strongsmell,andfreezing at ambienttemperatures. This investigationis aimedat comparingthe effectsof thesetwo oils alongwith that of coconutoil in preventinghair damagewhenusedasa preconditioner. Althoughseveral methodsinvolvingscanningelectronmicroscopy (SEM)measurement of combingforces andtensilemechanical properties havebeenusedearlierto characterize hair damage,we haveusedprotein lossand water uptakemethodsfor this purpose.Furthermore,these methodshavebeenextendedto studythe beneficialeffectsof theseoils in preventing chemical,thermal,andUV damage.Efficacyof thesemethodshasbeenestablished in an earlierpaperfrom this laboratory(3).

MATERIALS

AND

METHODS

MATERIALS

Samples of straight,curly,wavyandpermedhair of Indian originwereusedin thiswork. The length of the Indian hair strandswas 25 cm.

178

JOURNAL OF COSMETIC SCIENCE

200-

i

176

173

17 165 i

160 -

120PROTEIN

LOSS

ug/g OF HAIR

}92

IN

92 86

135&116

80-

40-

i

COCONUT OIL

SUNFLOWER OIL

COCONUT OIL

PRE-WASH TYPES OF OILS

IBWITHOUT

SUNFLOWER OIL

POST-WASH

EIWITH

Figure 1. Comparison of proteinlossfrom undamaged hair.

The reagentsfor protein estimationwereobtainedfrom SigmaChemicalCo. (St. Louis, MO). The otherreagentssuchasbuffersand saltswereof analyticalgrade,whereasthe oil sampleswereusedas they are availablecommercially. METHODS

Sample preparatio,.Hair tressesof 3+0.5 g were preparedfor this investigation.They were securedat the root end by a crochetsothat they remainedfirmly in place,and not a singlehair cameout of the tressduringexperimentation (eitherbecause of combingor during the procedure).They were cleanedby soakingin 0.01% (w/v) of polysorbate80 (30 min at 28øC), de-ionized water at room temperature (severalrinses),and 0.01% (w/v) of aceticacid (15 min at 28øC), in that order.Finally, they were extensivelyrinsed in water and air dried.

Bleachedhair was preparedby using a bleachingkit containing30 vol. hydrogen peroxideandammoniasolutionto adjustthe pH to -10. Fivemillilitersof thissolution wasusedper tress(cleanedby the procedurementionedearlier),and the treatmenttime was120 min at roomtemperature.With this treatmentthe tresses becamelight brown with

a red tone.

A boiling water treatmentwascarriedout for 120 min. The hair tresses wereplacedin

EFFECT OF COCONUT

OIL ON HAIR

227

DAMAGE

179

.....................................

240

200

145

160-

PROTEIN

LOSS

uglg OF HAIR

139 145140

IN 120-

80

40

0 COCONUT OIL

SUN FLOWER

PRE-WASHTYPES

BWITHOUT

COCONUT

OIL

SUN FLOWER

OIL

OF OILS

OIL

POST-WASH

DWITH

Figure 2. Comparisonof protein lossfrom bleachedhair.

a beakercontainingboiling distilledwater. The hair tresses were immersedin it. This wasnot doneto simulateany real-worldprocessbut in orderto createextremestressful conditions.This was primarily done to assess any impact on hair in water at high temperature,as Indian consumers largely usea hot water bath for hair.

In the caseof UV treatment,the hair tresses wereexposed to simulatedsunlightin a xenostat,whereineachhair tresswasexposedat 50øCand 65% relativehumidity for a periodof 300 hr. The tresses wereturnedoverduringtheperiodof exposure to attempt a uniform exposureof all fibersto the radiant source. In some caseshair tresses were treated with 0.2 ml of coconut oil/mineral

oil/sunflower

oil beforeexposure, with the oil spreaduniformlyacross the hair tressbeforeexposure to UV light. In a few cases,the treatmentwith oil wascarriedout afterUV exposure. The tresses werestoredat roomtemperaturefor 48 hr beforethey were subjectedto proteinlossdetermination. This wasdesignedto simulatedensityof hair on scalpand scalptreatments.

For the oil application,to eachhair tresswasapplied0.2 ml of oil (the quantity of oil normallyappliedby an Indian hair oil user).It wasallowedto remainon the hair for at least14 hr to simulateovernightapplication(the normalhabitof the Indianconsumer). Thesehair tresseswere then subjectedto both protein lossand WRI tests.

The entire studyinvolvedsamplesof straight,curly, wavy,and permedhair of Indian origin. Because the numberof variableswashigh, i.e., the type of oil, type of hair,

180

JOURNAL OF COSMETIC SCIENCE

360 -

306 320 280240 -

PROTEIN

LOSS

ug/g OF HAIR

IN

200 160 120 8040-

0

• COCONUT

OIL

I

I

SUNFLOWER OIL

PRE-WASH TYPES

l

[]WITHOUT

I

I

COCONUT

I

OIL

OF OILS

I

SUNFLOWER OIL

POST-WASH

[]WITH

Figure 3. Comparison of proteinlossfrom hair treatedwith boiling water.

sequence of oiling, the total numberof oil applications, and the numberof shampoo applications,the studyhad becomequite complexin nature.In orderto simplifythe complexityof the experiment, i.e., to reducecost,time, andenergywithoutcompromising on the quality of results,a statisticaltool wasselected,termedthe Taguchi Designof Experimentation. Thisis a toolusedin research anddevelopment of products in an engineeringindustrywherein,dependingupon the levelsand factors,an appropriatedesign,eitherorthogonal arrayor factorialdesign,is selected. Thishelpsto reduce the numberof experiments withoutaffectingthe result.Usingthis statisticalmodel,it waspossibleto completethe entirestudyin the stipulatedtime framewithout losing vital information,asit cut the numberof experiments to be conductedfrom 14400 to 800 (considering 25 hairtresses pervariable).As the experiment wasquitecomplex,we had to selectthe designof an orthogonalarray,L32, to conductthe experiment.The designof experimentwasaspresentedin Table I. The tresseswere wetted under running tap water (28øC) and washedwith a 20% solutionof sodiumlaureth(3 molesof EO) sulfate(SLES).One milliliter of the solution

wasappliedper tress,and the tresses wereworkedbetweenfingersto producea lather. Followingthis, they wereextensivelyrinsedto removeall the SLESresidues.After this treatmentthe tresses were subjectedto the followinginvestigations. Combingdamage. The protein loss method of Sandhuand Robbins was used in the

followingmanner.Eachof the wet tresses wascombedwith a fine-toothnyloncomb (20-22 teeth/inch)50 times,rathervigorouslyalongthe entirelength of the tresson

EFFECT

OF COCONUT

OIL ON

HAIR

DAMAGE

181

440400 36O 32O 253 280 240

PROTEIN

LOSS

ug/g OF HAIR

IN 200 160 120 80

400

COCONUT OIL

i

SUNFLOWER

COCONUT

OIL

PRE-WASH TYPES

SUNFLOWER

OIL

OF OILS

[]WITHOUT

OIL

POST-WASH

[]WITH

Figure 4. Comparison of proteinlossfrom hair exposed to UV treatment.

bothsides.After everyfive strokes,the combwasdippedin 50 ml of watercontained in a beakerto dislodge the debris.The same50 ml of waterwasusedto collectall the loosely heldproteinelutedfromthecombfora giventress.Theentiretresswasdipped in wateraftereveryfivestrokes to collectthe damaged anddislodged cuticlecells.The watersuspension wastestedfor proteincontentusingthe Lowrymethod.It wascomparedagainststandard bovineserumalbuminprocured fromSigmaChemical Co.This bovineserumalbuminwasdilutedsoasto getreadings withinwhichthemaximumand minimumreadingfor the samplewouldfall. The methodinvolves the formationof a copper-protein complex in alkalinesolution that,in turn,reacts withphosphomolybdicphosphotungstate reagent(Folin-Ciocaltaeu Phenolreagent)to yieldan intensebluecoloredsolution,whichis analyzed spectrophotometrically. It waschecked that the blue colordevelopment occurring in bothstandard andsamplewasof the samecolorwith differentintensity,depending on the amountof proteinbeingelutedfrom the hair fibers,therebyindicatingthatnoneof theoilswasinterferingin the colordevelopment. The methodology is discussed to a greatextentin reference (2). Water fete,rio, i,dex (WRI). The SLES-washed tresseswere soakedin a 0.01% solution

ofpolysorbate 80 for 30 min.Followingthisprocedure, theentiretresswasplacedover a hollowglasscylinderwith a glasslid with perforations to holdthetressproperlyand to separate the hair fromcapillarywaterin the glasscentrifuge tubeof diameter3 cm andheight8 cm.It wascentrifuged at 8000 rpmfor 15 min to removecapillarywater

182

JOURNAL OF COSMETIC SCIENCE

PROTEIN

LOSS

IN

ug/g OF HAIR 200

COCONUT

OIL

MINERAL OIL

SUNFLOWER

OIL

TYPES OF OILS

[] NORMAL WITHOUT

[] NORMAL

[] BLEACHED

[] BLEACHED

WITHOUT

WITH WITH

Figure 5. Comparison of proteinlossfrom normalandbleached hair in a salontrial.

andthenweighed.In thenextstep,thedryweightof thehairwasdetermined bydrying the tress in a vacuum oven at 50øC for 90 min, and then weighing it again. The

percentage waterretentionindex(WRI) is givenby:

WRI -- (Wwe t - Wary) 100/Wary Half-headtests, Eachhalf-headtest involved20 clientseachwith normalandbleached hair.The hairwaspartedin the middleandhalfthe headwastreatedwith the respective oil (3 ml approx.)and massaged thoroughly,while the other half wasleft without treatment.The oil wasleft on the hair for approximately8 hr. Then the hair waswashed with warmwater(28øC,200 ppm hardness) using20% SLES,andrinsedwell to remove

anyresidue.To avoidinherentdifferences in damagefromleft to right side,the application of the treatment was randomized. Panelists with odd numbers were treated on the

left side, while thosewith even numberswere treated on the right side.

After shampooing andrinsing,the hair wascombedwith a fine-toothcomb(separate

EFFECT OF COCONUT

OIL ON HAIR

Table

DAMAGE

183

III

Pair-Wise ComparisonData for Treatment Effectsfor Protein Loss(t-valuesat 95% confidencelevel) Treatment Undamaged--with and without MO (MO aspost-wash) Undamaged--with and without CNO (CNO as post-wash) Undamaged--with and without SFO (SFO aspost-wash) Undamaged--with and without MO (MO aspre-wash) Undamaged--with and without CNO (CNO as pre-wash) Undamaged--with and without SFO (SFO as pre-wash) and without MO Treatmentwith boiling water--with (MO aspost-wash) Treatmentwith boiling water--with and without CNO (CNO as post-wash) and without SFO Treatmentwith boiling water--with (SFO as post-wash) and without MO Treatmentwith boiling water--with (MO as pre-wash) and without CNO Treatment with boiling water--with (CNO as pre-wash) and without SFO Treatmentwith boiling water--with (SFO as pre-wash) Treatmentwith bleachingagent--with and without MO (MO as post-wash) Treatmentwith bleachingagent--with and without CNO (CNO as post-wash) Treatmentwith bleachingagent--with and without SFO (SFO as post-wash) Treatmentwith bleachingagent--with and without MO (MO as pre-wash) Treatment with bleachingagent--with and without CNO (CNO as pre-wash) Treatmentwith bleachingagent--with and without SFO (SFO as pre-wash) Exposureto UV light--with and without MO (MO as post-wash) Exposureto UV light--with and without CNO (CNO as post-wash) Exposureto UV light--with and without SFO (SFO as post-wash) Exposureto UV light--with and without MO (MO as pre-wash) Exposureto UV light--with and without CNO (CNO as pre-wash) Exposureto UV light--with and without SFO (SFO as pre-wash)

Straight

0.452

---

Wavy

--

0.106

1.779

--

-0.431

---

1.814

--

Curly

--

--

Permed

---

0.461 0.103 --

0.515

--

0.507

1.312

--

--

--

1.762

--

1.108

--

--

--

0.484

--

0.354

1.738

--

1.565 0.139

0.092 1.728 0.210

0.583

0.407

2.012

1.588

0.345

0.098 1.780

0.345

0.265

0.087

1.850

0.684

t theoreticalfor 48 degreesof freedomat 95% confidence level = 1.645.

combfor eachside).After eachof the ten combingstrokes,both the hair and the comb weredippedin 200 ml of distilledwater to recoverbrokencuticledebris.A total of 100 strokes(50 on eachside)wereapplied.The suspension with cuticledebriswasusedfor protein estimation.Analytical controlswere run in the form of determinationof the

184

JOURNAL OF COSMETICSCIENCE Table

IV

Analysisof VarianceData for Treatment Effectsfor ProteinLoss

Hair type

Sourceof variance

Degreesof Sumof Mean F-Valueat 95% freedom squares square confidence level

Undamaged Oil typeMO (straight,curly)

Between treatments

2

22.2

11.1

Experimental error

2

4.2

2.1

Undamaged Oil type MO (wavy,permed)

2

12.4

6.2

Experimentalerror

2

7.2

3.6

Between treatments Undamaged Oil type CNO (straight,wavy) Experimentalerror

2

92.8

46.4

2

2.0

1.0

Between

treatments

5.3

1.7 46.4

Undamaged Oil type SFO (curly, permed)

Between treatments

2

80.0

40.0

Experimentalerror

2

10.0

5.0

Boiled

Between treatments

Experimental error

2 2

32.4 4.6

16.2 2.3

7.1

Oil type MO (straight,curly)

8.0

Boiled

Between treatments

Experimentalerror

2 2

16.9 6.5

8.5 3.3

2.6

Oil typeMO (wavy,permed)

5.6

Boiled

Between

2

20.4

10.2

Oil type SFO (straight,wavy)

Experimental error

2

3.6

1.8

Boiled

Between

Experimental error

2 2

34.8 1.4

17.4 0.7

24.8

Oil type CNO (curly, permed)

treatments

treatments

Bleached

Between

Experimental error

2 2

4.2 4.2

2.1 2.1

1.0

Oil typeMO (straight,curly) Bleached

Between treatments

2

12.5

6.8

1.2

Oil type MO (wavy,permed)

Experimentalerror

2

11.5

5.8

Bleached

Between

Experimentalerror

2 2

38.0 7.8

19.0 3.9

5.0

Oil type SFO (wavy,straight) Bleached

Between

19.5

treatments

treatments

treatments

Oil type CNO (curly,permed) Experimental error

2

43.0

21.5

2

2.2

1.1

2

UV-Treated

Between

Experimental error

2

15.4 7.6

7.7 3.8

2.0

Oil type MO (wavy,permed) UV-Treated

Between

2

22.2

11.1

6.5

Oil typeMO (curly,straight)

Experimentalerror

2

2.3

1.7

UV-Treated

Between

2

10.4

5.2

Oil type SFO (wavy,straight)

Experimental error

2

2.1

1.1

UV-Treated

Between

2

44.6

22.3

2

1.2

treatments

treatments

treatments

treatments

Oil type CNO (curly,permed) Experimental error

4.7

37.2

0.6

F theoreticalfor (2.2) degrees of freedomat 95% confidence level = 19.0.

residue ofoilonthescalp oftheclientafterrinsing, andonlyafterensuring zeroresidue, the rinsingswere collectedin the mannermentionedabove.

Theoutcome of theseexperiments wasanalyzed statistically (takingintoaccount the meanandthestandard deviation ofthenumber of replicates forthesignificance of the treatment effects withinthe confidence limits).SeeTableII for analysis of variance (ANOVA)

data.

EFFECT

OF COCONUT

OIL ON

Table

HAIR

DAMAGE

185

V

Analysisof VarianceData for Treatment Effectsfor Water RetentionIndex

Hair type

Source variance

Degreesof freedom

Sum of Mean F-Value at 95% squares square confidencelevel

2

29.2

14.6

2

4.7

2.4

2

19.1

9.6

2

7.8

3.9

2

93.6

46.8

2

2.9

1.5

2 2

83.0 13.1

41.5 6.6

6.3

Experimentalerror

Boiled

Between

2

35.5

17.8

7.4

Oil type MO (straight,curly)

Experimentalerror

2

5.3

2.7

Boiled

Between

2

19.1

9.6

Oil type MO (wavy, permed)

Experimentalerror

2

7.8

3.9

Boiled

Between

Experimentalerror

2 2

20.4 4.2

10.2 2.1

4.8

Oil type SFO (straight,wavy) Boiled

Between

2

33.7

16.9

21.1

Oil type CNO (curly permed)

Experimentalerror

2

1.7

0.8

Bleached

Between

Experimentalerror

2 2

4.2 4.5

2.1 2.3

0.9

Oil type MO (straight,curly)

2 2

15.3 12.3

7.6 6.2

12.4

4.2

Between

treatments

Undamaged Oil type MO (straight, curly)

Experimentalerror

Undamaged Oil type MO (wavy, permed)

Experimentalerror

Between treatments Undamaged Oil type CNO (straight,wavy) Experimentalerror

Undamaged Oil type SFO (curly, perreed)

Between

Between

treatments

treatments

treatments

treatments

treatments

treatments

treatments

Bleached

Between

Oil type MO (wavy perreed)

Experimentalerror

treatments

Bleached

Between

2

40.0

20.0

Oil type SFO (wavy, straight)

Experimentalerror

2

9.5

4.8

Bleached

Between

treatments

6.2

2.4 31.2

2.4

2

40.0

20.0

Oil type CNO (curly, permed) Experimentalerror

2

1.8

0.9

UV-Treated

Between

2

17.4

8.7

Oil type MO (wavy, permed)

Experimentalerror

2

8.2

4.1

UV-Treated

Between

2

23.4

11.7

Oil type MO (curly, straight)

Experimentalerror

2

2.8

1.4

UV-Treated

Between

Experimentalerror

2 2

12.4 2.8

6.2 1.4

4.4

Oil type SFO (wavy, straight) UV-Treated

Between

Experimentalerror

2 2

41.6 1.6

20.8 0.8

26.0

Oil type CNO (curly, permed)

treatments

treatments

treatments

treatments

treatments

22.2

2.1

8.3

F theoreticalfor (2.2) degreesof freedomat 95% confidencelevel = 19.0. RESULTS PROTEIN

AND

DISCUSSION

LOSS

The process of cuticlechippingthat resultsfrom abrasionof hair againstobjectssuchas groomingdevicesor evenotherhair is a major factorin hair damage.The proteinsthat constitutethe cuticle cells are lost during wet combing.It is well known that wet

186

JOURNAL OF COSMETIC SCIENCE

15.3

5.•13.8

•'t14.1

14.9 145

12

% WATER RETENTION

INDEX

• :::: ß .•_,?..'..•,•

•'-•.. •:.

i

i

OIL

OIL

PRE-WASH TYPES

ltllWITHOUT

,}•{•'

. SUNFLOWER

COCONUT

. I

COCONUT OIL

OF OILS

I

SUNFLOWER Oil

POST-WASH

[3WITH

Figure 6. Comparison of waterretentionindexfor undamaged hair.

combingis accompanied by the breakingof the surfacecuticlecell because of its brittleness.Histologically,the major componentof the cuticle cell consistsof the exocuticleandthe endocuticle. The exocuticle,beinghighlycross-linked is not swollen by water.The endocuticle and the cell membranecomplex,on the otherhand,areless cross-linked andaremorevulnerableto swellingdamage.This leadsto the lifting of the

surface cuticlevia bending.Suchcuticlecellscanbe brokenin the process of combing or teasing.The proteinlossobserved in thesemeasurements resultsmostlyfrom the cuticularregion.Because of theshorttimeinvolvedin thecombingandbriefimmersion of the combedtressin water,it is unlikelythat proteinsfrom the bulk of the fiber are involved

in this measurement.

The datafor proteinlossmeasurement for undamaged anddifferentlydamaged hair are shownin Figures1-4. The barson theleft referto testswhereoil wasusedasa pre-wash conditioner,whereasthoseon the right arefor the testsinvolvingpost-washtreatments

whereoil wasappliedafterdryingthe hair.The datain Figures1-4 clearlyshowthat theperformance of coconut oil in reducingproteinlosswasbetterthanthat of mineral andsunfloweroils.Coconutoil performedbetterasa pre-washratherthan a post-wash conditioner. This showsthe importance of lubricationvs reductionin the swellingof the cuticlecellsthat leadsto their breakingin wet combing.The differencebetween

EFFECT

60-(

OF COCONUT

i•

ß 45

52 3

OIL ON

•[• 52 4

.?•

.

•

ß

'•

SUNFLOWER OIL

PRE-WASH TYPES

J

'50.9"",

•

COCONUT OIL

187

52 3

' 0.4 'i'

{

INDEX

DAMAGE

•

.{

RETENTION 30

HAIR

COCONUT OIL

SUNFLOWER OIL

OF OILS POST-WASH

BWITHOUT

E3WITHJ

Figure 7. Comparisonof water retentionindex for bleachedhair.

coconutoil andmineraloil is probablydueto the differencein their ability to penetrate the hair (4). The smallereffectof sunfloweroil may be due to the presence of unsaturationin the molecule.No informationregardingthe penetrabilityof sunfloweroil in the hair is available.The sameeffectwasseenin the half-headtest in a salontrial, asseen in Figure 5.

The effectof variousoilsin preventingcuticledamagein laboratorytestswasestablished statisticallyby a parametrictest,t-test. The outcomeof the analysisis shownin Table III. The t-valuesclearlyindicatethat damagedaswell asundamagedhair benefitsfrom applicationof coconutoil asa pre-washconditioner,whereasin the caseof sunfloweroil and mineral oil, there was no effect.The effectsof coconutoil were alsopositivein a salontest.In both normalandbleachedhair, treatmenteffectsin reducingproteinloss weresignificant,whereasthe samefindingswereabsentin the caseof mineral oil and sunfloweroil. The valuesof t for coconutoil are statisticallysignificant,whereasfor mineral oil and sunfloweroil, they are not.

SeeTablesIV andV for ANOVA data for treatmenteffectsfor proteinlossand water retention

index.

188

JOURNAL OF COSMETIC SCIENCE

24.2

% WATER

RETENTION INDEX

10-

COCONUT

SUNFLOWER

OIL

OIL

PRE-WASH TYPES

•WITHOUT

COCONUT

SUNFLOWER

OIL

OF OILS

OIL

POST-WASH

EIWITH

Figure 8. Comparisonof water retentionindexfor hair treatedwith boiling water. WATER

RETENTION

INDEX

The waterretentionindexfor undamaged hair is shownin Figure6. Fromthe datait can beseenthatcoconutoil reduces theWRI of undamaged hairby 44%, whereas in the case of mineraloil and sunfloweroil, thereis hardlyany reductionin WRI, asseenin Figure 6. The ability of coconutoil to penetratehair (4) supportsthis observation. The data for the bleached,heat-damaged, and UV-damagedhair are shownin Figures 7-9, respectively. For thesedamagedsamples,the WRI is muchhigherthan that for the undamagedhair. This is mostlydue to the chemicaldegradationof proteins,generating hydrophilicgroups.Both the cleavageand oxidationof disulfidebonds,followedby their oxidationto cysteicacid, as well as hydrolysisof the peptide linkage, occur, althoughthe contributionof the latter is probablyminor. All samplesshowa reduction in the WRI asa resultof the applicationof coconutoil, whereasthe samefindingswere not observedto a significantlevel in the caseof mineraloil and sunfloweroil. Assuming that mostof the wateris absorbed by the fiber, the WRI reflectsthe swellingpropensity

EFFECT OF COCONUT

i59.8 ß

OIL ON HAIR

DAMAGE

61.2

189

61.2

•,..•8.7

5

57.5

60

x::":• % WATER

RETENTION

40

INDEX

20-

SUNFLOWER OIL

COCONUT OIL

PRE-WASH TYPES

COCONUT

SUNFLOWER

OIL

OF OILS

EIWITHOUT

OIL

POST-WASH

EIWITH

Figure 9. Comparisonof water retentionindex for UV-treated hair.

of hair. Sincerepeatedswellingand contractiondamagesthe cuticle,reductionin the WRI can be considered as beneficialin reducinghair damage.

The datain Figures6-9 showthat the sequence of application(whetherpre- or postwash) is important. Post-washapplicationis lesseffectivein reducingthe WRI as comparedto pre-washapplication.The differenceseemsto be in the locationof the oil residues andtheir ability to counteract surfactantdamage.In post-wash applicationthe

oil film is on the surface, with nopenetration into the fiber.In pre-wash application, it ispossible that the molecules of the oil penetrateinto the cuticleandprobablyeveninto the cortex.This may alsobe the casewith undamagedhair, althoughthe effectis small. The reductionin the WRI mustbe dueto the introductionof the hydrophobic triglyc~ eride into the keratin

structure.

SeeTableVI for pair-wisecomparison of treatmenteffectsfor waterretentionindexdata. MECHANISM

OF PROTECTION

BY COCONUT

OIL AND

NOT

BY MINERAL

OIL AND

SUNFLOWER

OIL

The histologyof a cuticlecellandthe mechanism of damagein wet combingisproposed by Swift (5,6) Because of cross-linking, the exocuticleis brittle anddoesnot swell.The

190

JOURNAL OF COSMETIC SCIENCE Table

VI

Pair-Wise ComparisonData for Treatment Effectsfor Water RetentionIndex (t-valuesat 95% confidencelevel)

Treatment

Straight

Wavy

Undamaged--with and without MO (MO as post-wash) Undamaged--with and without CNO (CNO as post-wash) Undamaged--with and without SFO (SFO as post-wash) Undamaged--with and without MO (MO as pre-wash) Undamaged--with and without CNO (CNO as pre-wash) Undamaged--with and without SFO (SFO as pre-wash) Treatmentwith boiling water--with and without MO (MO as post-wash) Treatmentwith boiling water--with and without CNO (CNO as post-wash) Treatmentwith boiling water--with and without SFO (SFO as post-wash)

0.41

--

Curly

Permed

O.O9

1.87

--

--

--

O.36

--

O.O9

O.34

--

1.98

O.34

__

0.43

1.21

1.89 1.02

Treatmentwith boilingwater--with and without MO (MO as pre-wash) Treatmentwith boiling water--with and without CNO (CNO as pre-wash) Treatmentwith boilingwater--with and without SFO (SFO as pre-wash) Treatmentwith bleachingagent--with and without MO (MO as post-wash) Treatmentwith bleachingagent--with and without

0.24

0.13 1.85

1.43 0.06

0.12

1.87

CNO (CNO as post-wash)

Treatmentwith bleachingagent--with and without SFO (SFO aspost-wash) Treatmentwith bleachingagent--with and without MO (MO aspre-wash) Treatmentw•th bleachingagent--with and without

0.12

0.46

O.47

2.12

CNO (CNO as pre-wash)

Treatmentwith bleachingagent--with and without SFO (SFO as pre-wash) Exposureto UV light--with post-wash) Exposureto UV light--with post-wash) Exposureto UV light--with post-wash) Exposureto UV light--with pre-wash) Exposureto UV light--with pre-wash) Exposureto UV light--with pre-wash)

1.45

and without MO (MO as 0.21

0.098

and without CNO (CNO as 1.85

and without SFO (SFO as 0.32

and without MO (MO as 0.19

0.09

and without CNO (CNO as 1.97

and without SFO (SFO as O.43

t theoreticalfor 48 degreesof f}eedomat 95% confidence level = 1.645.

endocuticleand the cell membranecomplexhavelesscross-linkingand thereforeswell significantly.This effectproducesthe tendencyfor the surfacecuticle cells to curve upwardand breakwhen pressureis appliedwith a comb.

Recentstudiesof Ruetschand Weigmann(7) confirmthat the endocuticleandthe cell

EFFECT OF COCONUT

OIL ON HAIR

DAMAGE

191

membranecomplex(CMC) are the foci of weaknessand that the cuticle cell often lifts and fractureswhen the fiber is extended.Chemicalmethodsimpair the adhesionby weakeningthe cell membranecomplexbetweenthe cuticlecells.The degreeof swelling of the cuticlelayersis increased by disulfidecleavageand oxidation.This enhances the combingdamageandproteinloss,especiallyin wet combing,asobservedin this study. Coconutoil is mostly a triglycerideof lauric acid and is hydrophobic.Application of coconutoil asa pre-washconditionercoatsthe hair andinhibitsthe penetrationof water into the hair. A smallpart of it is alsoabsorbedinto the hair during the washwhen the fiber is swollen.Introductionof this hydrophobiccomponentreducesthe swelling propensityof the cuticle,which limits the upwardcurvingof the surfacecuticle.This reducesthe chippingawayof the cuticlecells,which reduces proteinloss,asobservedin this work.

Becauseof the low molecularweight of coconutoil, it penetratesthe cortex,whereas mineraloil, beinga hydrocarbon, doesnot penetratethe hair at all. This hasbeenshown in the earlierstudy (4). It is possiblethat sunfloweroil doesnot penetratethe fiber becauseit hasa bulkier structureas a resultof doublebondsin the fatty acid chain. Coconutoil triglyceridehas a linear structure,which is why it solidifiesat room temperature,whereassunflowertriglyceridehasan irregularball-like structurebecause the fatty acid chainsfold on themselves due to oneor two doublebonds.This is why sunfloweroil is a liquid at room temperature.It is likely that it doesnot penetratethe fiber aswell asthe coconutoil. This may be the reasonwhy the WRI is low for coconut oil as comparedto mineral and sunfloweroils. CONCLUSIONS

This studyhasfirmly established the superiorityof the protectiveeffectof coconutoil on hair damagein grooming processes when it is used as a pre-washconditioneras comparedto mineral oil and other vegetableoils suchas sunfloweroil. It not only has a protectiveeffecton undamagedhair but alsoon chemicallytreatedhair, UV-treated hair, and hair treatedwith boiling water (i.e., hair in water at 100øC for 2 hr). The ability of coconutoil to penetrateinto hair cuticleandcortexseemsto be responsible for this effect.Coatedon the fiber surface,it can preventor reducethe amountof water penetratinginto the fiber and reducethe swelling.This, in turn, reducesthe lifting of the surfacecuticleand preventsit from being chippedaway during wet combing.A

reductionin the WRI is additionalevidenceof its efficacyin decreasing waterabsorption. The datapresentedin thiswork clearlyshowthe superiorityof coconutoil asa hair damageprotectant,in the groomingof untreatedor damagedhair. ACKNOWLEDGMENTS

The authorsthank the management of MaricoIndustriesLtd. for providingan opportunity to work on this project, and Dr Yash Kamath, Director of Research,T.R.I., Princeton,New Jersey,for his valuableguidancein writing this paper. REFERENCES

(1) M.L. Garcia and J. Diaz, Combabilitymeasurements on human hair, J. Soc.Cosmet. Chem.,27, 379-398 (1976).

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JOURNAL OF COSMETIC SCIENCE

(2) S.S. Sandhuand C. Robbins,A simpleand sensitivetechnique,basedon protein lossmeasurement,

to assess surfacedamageto humanhair,J. Soc.Cosmet. Chem.,44, 163-175 (1993). (3) A. Rele, Effectof coconutoil on preventionof hair damage.Part I,J. Cosmet. Sci.,50, 327-339 (1999). (4) S. B. Ruetsch,Y. K. Kamath, A. S. Rele, and R. B. Mohile. Secondary ion massspectrometricinvestigationof penetrationof coconutandmineraloilsinto humanhair fibers:Relevance to hair damage,

J. Cosmet. Sd., 52, 169-184 (2001). (5) J. A. Swift and A. C. Brown,The criticaldeterminationof fine changes in the surfacearchitecture of humanhair due to cosmetic treatments, J. Soc.Cosmet. Chon.,23, 695-702 (1972). (6) J. A. Swift, Int. J. Cosmet. Sci,,13, 143 (1991). (7) S. B. Ruetschand H. D. Weigmann,J, Soc.Cosmet. Chem.,47, 13-26 (1996).