HAIR CARE Original presentation by: Assoc. Prof. Dr.Pleumchitt Rojanapanthu Pharmacy Department, Faculty of Pharmacy Mahidol University, Bangkok, Thailand Edited by: Ellen Berwick

Hair Getting to know hair Types of hair Hair structure Hair growth cycle Hair Color Physical properties of hair Chemical properties of hair

Hair Care Products that affect Chemistry Shampoos Conditioners “2 in 1” shampoos Hair sprays Hair gels Perming solutions Hair dyes General remarks about product development

Getting to Know Hair All land mammals including humans have hairy skins Hair characteristics (like your eyes and skin) are inherited directly from our parents hair color hair type

Hair distribution Human are covered all over in hair except on the palms of hands the sole of the feet the lips Hair is most obvious on the head and face including the nose and ears in some people the armpits / the groin the chest and legs (in men)

How much hair do we have Average : 100,000-150,000 hair follicles Baby’s head : 1,100 follicles/m2 Age 25 : ~ 600/m2 Age 30-50 : ~ 250-300/m2 Each follicle grow about 20 new hairs in lifetime Each new hair grows several year 1 meter Each hair falls out eventually and is replaced by a new hair

Variation in human hair Different people have hair that differs in color, length, diameter, distribution Influence factors : Racial type and Age

Three types of hair: Lanuga hair develops on an unborn baby 3 months after the baby’s conception fine and soft grows all over the body, at the same rate shed about 4 weeks before the baby is due to born

Vellus hairs short hair, only 1 or 2 cm long contains little or no pigment follicle doesn’t have oil glands

Terminal hairs long hairs that grow on the head, body, arms and legs produced by follicles with sebaceous glands people inherited a tendency for baldness where the hair become thinner and shorter until look like vellus hair

d Vellus hairs on a woman’s chin. These are normal when female hormones decline, hairs on the chin can grow as strongly as terminal hairs

Hair Structure Hair follicle a tiny cup-shaped pit buried deep in the fat of the scalp follicle is the point from which the hair grows well supplied with minute blood vessels temperature is not affected by cold or hot water the rate of growth depends on the amount of natural light : growing a little faster in winter when the days are short

Hair follicle Hair bulb Hair shaft Hair bulb - lines in side the hair follicle - is a structure of actively growing cells - produce a long fine cylinder of hair - new cells are continuously produced in the lower part of the bulb

(a) Longitudinal section of a hair within its follicle. (b) Enlarged longitudinal section of a hair.

(c) Enlarged longitudinal view of the expanded hair bulb of the follicle which encloses the matrix, actively dividing epithelial cells that produce the hair.

(d) Cross section of a hair and hair follicle.

(e) Photomicrograph of scalp tissue showing numerous hair follicles (24 X).

Scanning electron micrograph showing a hair shaft emerging from a follicle at the epidermal surface. Notice how the scalelike cells of the cuticle overlap one another (1500 x).

The Hair Shaft can be seen above the scalp consist mainly of dead cells Keratin + binding material + small amount of water terminal hairs are lubricated by natural oil (sebum) produced by sebaceous glands high level of hormones (androgens) high level of sebum

Nature of cuticle scales growing over the youngest part (closet to the scalp) are smooth and unbroken further along the hair have been damaged by cosmetic treatments and by mistreatment : (over-energetic brushing)

Nature of cuticle (con.) little by little, they may break away : “weathering” healthy cuticle is more than just a protective layer intact cuticle cells are smooth, glossy, and reflect light from their surface (black hair reflects less light than blond hair)

The cuticle scale on a normal hair (electronmicrograph)

A perfect hair seen under the electron microscope Another normal hair - but this came from one of our nearest relatives an orangutan!

Hair shape keratin chains link by : disulphide bond and hydrogen bonds disulphide bonds can be changed by chemical methods : perming and relaxing permanent hydrogen bonds can be easily broken apart whenever the hair is wetted and form again as it dries when they break the shape of hair changes wet hair is wound on the roller, the dried hair keeps the roller shape temporary

Hair dimensions European around 70-90 micron Asian around 120 micron People have average hair around 100,000 – 150,000 hairs

Hair growth cycle individual hair form inside a hair bulb deep in hair follicle is tiny but powerful factory each hair grows during many years shampooed, conditioned, cut, blown dry, exposal to the sun and wind, colored, bleached, permed none of these affected the hair growth the hair spontaneously falls out the follicle rests for a little while and starts to produce a new hair

Stage of the hair cycle anagen : the growing phase (~1000 days) catagen : the intermediate phase (~10 days) telogen : the shedding phase (~100 days)

Anagen (the growing phase) last between 3-7 years without interruption roughly 1 cm/month > 1 meter faster rate in winter than summer melanin is made in hair bulb throughout this phase less pigment is made in older people, hair cycle becomes shorter follicles gradually give up producing long, strong hair : hairs become thinner and shorter thinning of the hair degree of baldness

Catagen (the intermediate phase) short resting phase : 2-4 weeks no pigment is made follicles stop producing hair the base of follicle moves upwards towards the surface of the skin

Telogen (the shedding phase) last for 3-4 months new hair begin to grow from the hair follicle as it grow s upwards the old hair will be shed naturally or easily be pulled out at anytime around one in ten of the follicles at individual’s head is in the shedding phase shedding is part of normal process of the replacement of old hair with new hair new hair emerges from the same opening as the old one

The hair follicle cycle

A method of measuring the rate of hair growth: both cut hairs and newly emerging hairs can be seen

Electronmicrograph showing new hairs emerging from the hair follicles of the scalp

What controls hair growth ? general health and nutritional factors starvation or crash diet loosing hair in 6-10 weeks alcoholic people have poor hair some minerals may particularly important for hair growth

Hair growth (con.) lack of Zn : produces only fine, sparse hairs even lost their hairs Vit B : known as panthenol, plays a part in hair growth, improves physical properties (elasticity, strength and gloss) of the hair shaft

Hormones : thyroid hormone speeds up growth in resting hair follicles steroids taken by mouth slow down the growth

Hormones (con.) Androgen : the most important factor regulating hair growth, thickness of hair shaft : changes vellus - like hair terminal hair oestrogen : slow down hair growth during growth period, make the period longer

 This boy has a zinc deficiency, and his hair is very thin and sparse; after treatment his hair is growing more strongly

Hair Color Pigmentation Melanin : - produced by melanocytes at growing phase (anagen) - spread out throughout the cortex, the more near outer edge - does not protect the harmful effect from sunlight - is found in 2 forms Eumelanin : dark pigmented which predominates in black and brunette hair/oval shape Phaeomelain : lighter pigment, found in red and blond hair/smaller, partly oval and partly rod- shape

Melanin granules in the cortex of a hair

Factors affecting hair structure : the arrangement of keratin bundles the way the large bundles of keratin are arranged within each hair shaft the position of hair bulb : African hair bulb may lie to the side of the follicle, so the hair shaft grows out of the follicle at an acute angle

Factors affecting hair structure (con.) irregular growth in the hair bulb : if it varies slightly to one side or the other, hair may grow wavy the shape of the follicle : whether it is straight or curved the number of twists per unit length : African hair has 12 times as many twist per cm. as Caucasian hair

Physical properties of hair Strength Elasticity Static electricity Moisture content Porosity Texture

Hair strength a single hair can support a load of about 100 gm keratin protein of the cortex responsible for the hair strength keratin is a protein chains contain high concentration of an amino acid called “cystine” matrix contains high level of cystine

Hair strength (con.) each cystine unit contains 2 cysteine amino acids in different chain the chains are linked by two sulphur atoms, forming a very strong chemical bond “disulphide linkage” many disulphide bonds form down the length of the keratin chains

Chemical bonds within the hair maintain its shape

Elasticity one of the most important properties can resist forces that could change its shape, volume and length lest spring back to its original form without damage wet hair can increase the length up to 30% and return to original length when it is dried

Elasticity (con.) elasticity of hair depends on the long keratin fibers in the cortex chemical treatment can alter the cortex and change the hair elasticity

Elasticity (con.) poor elasticity : - stretch only to a limited extent - will break easily - cannot be permed satisfactorily natural sunlight and artificial UV light damage chemicals of hair and its elasticity

Static electricity rubbing drug hair / brushing / combing builds up static electric charge the charges tend to push each other apart charged hair never lie smooth against each other “ fly away ” hair stands out from the head

Moisture content : less moisture more static electricity more volume Heat and humidity more moisture less static electricity collapse Heat and dryness less moisture more static electricity more volume

Moisture content (con.) - wet hair swell cortex / lift cuticle scales - hair surface temporally loses its smoothness - wet hair more friction matting and tangles (over vigorous shampoo)

Porosity Normal hair cuticle covering cortex is intact : almost water proof (very little water can go in and out) shampoos do not damage the cuticle treating the hair (permed or tinted)

Porosity (con.) temperature / applying an alkaline lotion separate the scale allowing chemicals to go inside after processing scales close up

Porosity (con.) processing many times / too much blow drying/ too high temperative / effect of sun and wind the scales lose the tightness the porous damage cuticle is fragile develop split end

Porosity (con.) the damage is worse as the time goes by the greater the damage, the more the cortex swells with water the more water loses when it dries repeated wetting and drying of the cortex, gradually weakens the hair

Texture the larger the hair diameter the coarser it will feel different people’s hair naturally feel different soft / hard / silky / wiry effected by degree of weathering of hair

Texture (con.) Texture is affected by what has been put on it : - spray : makes different feeling - conditioner : feel soft and smooth - conditioner with silicone : protect the hair cuticle - damage to cuticle : alter the hair texture

Chemistry of Hair Keratinization process in the follicle keratin + water soluble substances : pentose, phenols, uric acid, glycogen, glutamic acid, valine, leucine

Chemistry of Hair (con.) Keratin is composed of amino acid 18 out of 25 normal amino acids are found in keratin

Chemistry of Hair (con.) Organization of hair protein sets up by bonding in 3 ways : I Formation of H-bonds between parallel peptide chains

Chemistry of Hair (con.) II Formation of salt linkage between acidic and basic side chain

Chemistry of Hair (con.) III Formation of disulphide linkages amino acid contains two amino and two carlygl groups link together by a disulphide bond

Structure for a- keratin