L12: Hair Cosmetics Flashcards
What are the general functions of hair?
- Natural function
- Social function
- Psychological function
What are the main structural components of the hair?
- Hair follicle
- Hair bulb
- Hair shaft
- Sebaceous gland
- Arrector pili muscle
What are the 3 layers of the hair shaft, starting from the outermost layer?
- Cuticle
- Cortex
- Medulla
What are the characteristics of the cuticle of the hair shaft?
- Overlapping scale-like structure made up of translucent, non-pigmented cells
- Composed of hard keratin protein
- Makes up 10 - 15% of the hair
What are the characteristics of the cortex of the hair shaft?
- Made up of densely packed spindle-shaped cells aligned along the long axis of the hair on the inner face of the cuticle
- Contains melanin granules that determine the hair colour
- Makes up 85 - 90% of the hair
What is the characteristic of the medulla of the hair shaft?
- Composed of honeycomb-like cells
Which layer of the hair shaft is not found in vellus hair and infant hair?
Medulla
Which layer of the hair shaft is responsible for brighter hair?
Medulla
Which layer of the hair shaft is responsible for the smoothness and softness of the hair?
Cortex
Which layer of the hair shaft confers protection and strength to the hair?
Cuticle
Why do we need to use conditioners for our hair?
To moderate static charges between hairs, as well as between hair and other materials for better manageability
How are charges formed on the hair?
- Rubbing
- Shampooing
What cause the hair to entangle easily?
Repulsive forces caused by electrical static charges formed on the hair
What may cause the strength of hair to decrease?
- Wet hair
- Deficiency in proteins
Are the number of hair follicles fixed at birth?
Yes
At which stage in life causes hair roots to thicken?
Puberty
What is responsible for the thickening of hair roots during puberty?
Androgens
What is the difference between terminal hair and vellus hair?
Terminal hair is thicker and darker, while vellus hair is less visible, finer and lighter in color.
Before puberty, terminal hair is limited to which body parts?
- Scalp
- Eyebrows
- Eyelashes
What are the 3 phases of the hair cycle?
- Anagen (Hair growth)
- Catagen (Growth stops)
- Telogen (Hair loss)
What are the two main hair growth patterns?
- Whorl
2. Cowlick
What are the three types of hair?
- Straight
- Wavy
- Curly
How can the cross-sectional shape of the hair be assessed via?
Hair diameter index (= minor axis/major axis)
Which is more fragile, curly hair or straight hair? Why?
Curly hair. It has the lowest hair diameter index and stretches less under mechanical stress = more likely to break
Which part of the hair determines the hair type?
Shape of the hair bulb
What causes gray hair in aged individuals?
Slowed or stopped production of melanin
Can hair graying be reversed by supplements etc.?
No.
What causes baldness?
Shrinkage of hair follicle, thus producing finer hair and the cycle eventually stops
Which medication can help with baldness and how?
Minoxidil, by widening blood vessels to nourish the hair follicles
Other than medication, what are some other ways to treat baldness?
- Hair transplant
- Testosterone replacement
- Microneedling
- Stem cell therapy
What chemical bonds can be found in the hair and what are their respective characteristics?
- S-S disulphide bonds: promote curls
- CO-NH peptidic bonds: Strongest
- Ionic bonds: Can be broken down by acidic or basic solutions
- Hydrogen bonds: Affected when hair is soaked in water; converts from alpha- to beta-keratin
What are the 3 main causes of hair damage?
- Chemical
- Environmental
- Physical
What are some characteristics of damaged hair?
- Dry and brittle
- Colour changes to reddish (due to breakdown of eumelanin)
- Has split and broken ends
Which type of ingredients does a shampoo contain that does not contribute to the cleansing ability of shampoos?
- Foaming agent
- Thickeners/Opacifiers
Why does the second application of shampoo cause more foam?
Sebum impairs the lathering ability of foaming agents during the first application
Why are shampoos that only cleans not favourable?
It is because clean hair is dull in appearance, coarse to touch and is subjected to static electricity
What is the main characteristic needed in surfactant molecules?
Amphiphilicity
Name some deep cleansing surfactant.
- Lauryl sulfates
- Laureth sulfates
Name a mild surfactant.
Betaines (amphoteric)
Name some surfactants used in an everyday shampoo for entangled hair.
- Amnioesters (cationic)
- Polyoxyethylene (nonionic)
What are the 3 main types of conditioning agents?
- Quarternaries (eg. stearalkonium chloride)
- Film forming (eg. polyvinylpyrrolidone)
- Hydrolyzed silk protein
What are the 3 main types of conditioners?
- Instant conditioners
- Deep conditioners
- Leave-on conditioners
Other than conditioning agents, what are some other ingredients that is important to have in a conditioner?
- Moisturizing agents/Humectants
- pH adjusters (as conditioners are usually acidic)
What is an example of a pH adjuster?
Citric acid
What is an example of a foaming agent?
Cocodiethanolamide
Which type of ingredient provide the pearlescent effect in shampoos? Give 2 examples.
Thickeners/Opacifiers.
- Glycol distearate
- PEG-150 distearate
What are the 4 main types of hair styling cosmetics and what are their respective functions?
- Hair spray: keeps the hair styled
- Hair gel: Can style both wet and dry hair
- Hair mousse: Can be used to cover gray hair temporarily
- Hair serum: to repair damaged hair
Why does non-electric hair styling devices require wet hair?
Moisture allows the transformation of keratin from alpha to beta through disruption of hydrogen and ionic bonds.
During drying, new bonds are formed, thus blocking the hair from returning to natural alpha keratin
Note: wetting the hair returns the hair to the natural alpha configuration
Rank the following according the amount of disulfide linkages being altered, starting from the lowest %.
- Permanent waving
- Hair straightening
- Moderate bleaching
- Severe bleaching
- Permanent waving / Moderate bleaching (~20%)
- Hair straightening (~35%)
- Severe bleaching (~40%)
Which hair treatments uses an alkaline pH?
- Permanent waving (pH 8 - 9.5)
- Hair straightening (pH 13)
- Semi-permanent hair coloring
- Permanent hair coloring
What is process of permanent waving?
- Washing hair to remove sebum
- Breakage of existing S-S bonds using a reducing agent (ammonium thioglycolate at pH 8 to 9.5; sodium thioglycolate if ammonia-free)
- New S-S bonds made using an oxidizing agent (hydrogen peroxide)
What is the process of hair straightening?
- No shampooing (need protection from the sebum)
- Apply petrolatum to scalp and hairline
- Apply relaxer cream (sodium hydroxide) with pH 13 and comb straight
- Rinse within 20 min and apply neutralizer and conditioner
What are the 4 types of hair coloring methods?
- Gradual/metallic/progressive
- Temporary
- Semi-permanent
- Permanent
