Hair, Scalp and Gender

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Keratin coiled-coil. Cortex - 80%. • Major part of fibre mass in human hair. • 1-6μm thick ... Human hair contains only one type of cortical cell .... Straightening /.
Hair, Scalp and Gender GRAHAM TURNER, CBIOL, FRSB UNILEVER RESEARCH & DEVELOPMENT

Declaring and Disclosing Conflict of Interest Name of the speaker: Graham A.Turner Presentation title: I have an affiliation (financial or otherwise) with a pharmaceutical, medical device, or communications organization. If yes, Details : Paid employee of Unilever plc

Hair is the ultimate personal beauty tool of self-expression

Hair fibre composition and structure Cortex - 80% Fibre structure • Major part of fibre mass in human hair • 1-6mm thick and approx. 100mm long • Human hair contains only one type of cortical cell • Cells contain fibrillar (crystalline - 60%) and non-fibrillar (amorphous - 30%) protein • Cortex made up almost entirely of keratin

Cuticle - 20% Keratin coiled-coil Microfibril Macrofibril Cortical cell

Cortex Cuticle 4

Hair shape and ethnicity

Hair fibres grow differently in ethnic groups. However, no gender differences Observed within ethnic groups. 5

Hair diameter and gender • Optimum approach to measure fibre diameter is with a laser scanning micrometer (takes cross section into account). • Most published reports do NOT apply such rigour. Conflicting results. No clear difference with gender. • Indian population. Trend to increased diameter and degree of medullation in males (Gaur et al, 2007)

• Females had higher Hair Area (HA) than males between ages 50-69 (Srettabunjong et al, 2016). Used microscopy to measure hair diameter.

Defined Hair Area (HA) as: minor diameter x major diameter x 𝜋 4

But: Somali (Pacini et al, 1984) and Indian males (Das-Chaudhuri and Chopra, 1984) had thicker hair (racial differences?) 6

Hair physical properties

Bending

Torsion Tension

Men

Women

Significance

Hair Break Force (mN)

664±268

752±223

N.S. (p=0.067)

Young’s Modulus (Nm-2)

0.1962

0.2303

N.S.

Erik et al, 2007

Johri & Jatar, 1982

Cystine/Cysteine content

Men>Women

Significant

Clay et al, 1940

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Males and females have different scalp needs Scalp Needs and Concerns

Less dandruff

15%

Less itchy scalp

10%

Less greasy

8%

Less greasy scalp

5%

Less sensitive scalp Less dry scalp

4% 2%

Less dandruff

24%

Less itchy scalp

16%

Less greasy

12%

Less greasy scalp

9%

Less sensitive scalp Less dry scalp

7% 3%

Globally, men experience more issues with scalp health than women •

Unilever H&A studies: All respondents – Brazil (1002), Turkey (989), Russia (1010), India (3208), China (2006), Indonesia (1224), Japan (1127) 8

Male and female scalps are different 600 500 200 400

Mean sebum

Total protein (μg)

250

300 200

150 100

100

50

0

0 Female

Male

 Men lose more protein than women  Men more prone to dandruff

Female

Male

 Scalp sebum levels were higher in males than in females (1.5 times greasier than females)

Unilever Clinical studies: BKK-BIO-GEN and SW-DDF-08-001 9

Male and female scalps are different 0.2

Ceramide (µg/µg protein)

0.18

Antidandruff benefit (TWHS reduction)

0.16 0.14 0.12 0.1

0.08

0.06 0.04 0.02 0 Men

Women

• Men have lower ceramide levels in SC of scalp (weaker SC barrier; higher TEWL) • Weaker barrier makes men more prone to dandruff • Men have a greater response to antidandruff shampoo (Clear AD Shampoo, 1% zinc pyrithione) *

* Meta-analysis from 4 Unilever studies in Bangkok, 2003-2005

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Hair Growth and Gender • Linear Hair Growth Rate (LHGR) faster for women than men for all but the thickest hair (≥60µm)

- (Van Neste & Rushton, 2016)

• In balding men , LHGR decreases. In females with FPHL, LHGR decreases only for the finer hairs.

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Hair Loss Hamilton-Norwood Scale of Male Pattern Hair Loss

Savin Scale of Female Pattern Hair Loss

• The most obvious difference between men and women is in the area of androgenetic alopecia • Incidence is higher in men and starts at much younger age (some in early 20’s) • FPHL is often accredited to postmenopause (6% of women under age of 50; 38% in women aged >70) Messenger et al (2001)

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Hair treatment habits and damage Causes

- Pollution

Effects

- Dry feel

Tactile

Environment - Sunlight - Hair Drying

Process

- Roughness - Tangling

- Heat Styling - Combing / brushing

- Frizz

Look

- Loss of movement - Weakness / Fragility

- Colouring / bleaching

Chemical - Straightening / waving

Structural - Breakage

Increasing Damage Severity

- Split ends

Hair damage

Cuticle starts to break down

Healthy hair

Split ends appear

Cuticle disappears & Cortex is exposed

Hair breaks 14

Hair Damage Characteristics • Mechanism for fibre degradation is differentiated for physical and chemical processes Physical damage

Chemical damage

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Summary • There are no major gender differences in hair fibre structure or physical properties • Hair styling and treatments result in more damage to the fibre (mainly an issue with women)

• Women have a faster LHGR than men. • Males and females have different scalp needs • Men report more dandruff, itch and “grease” (sebum)

• Men have weaker scalp SC barrier (lower ceramide and “extractable” protein) • Men respond more positively to antidandruff treatment (ZPTO)

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Acknowledgements Unilever R&D Port Sunlight Fiona Baines Jane Matheson Jennifer Yates Joe Muscat

Unilever R&D Shanghai Echo Pi Marina Bian

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