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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