Mixed Hair Types & Straight Hair | Curly Hair

Over many thousands of years these three groups of people have intermingled. Their descendants now show every imaginable blend of hair type and color.

Of the three racial groups, the Caucasoids are by far the most varied in the appearance of their hair. It may fall completely straight, it may be crinkly or wavy, or it may form large curls, or pretty well anything in between. Blondes tend to have straight hair, while more brunettes have curly hair. The longer the hair grows, the more obvious its basic character becomes. The first month or two's growth of a new hair may be straight, but then it may start to curl or wave.

Types of Hair Variations

Scientists do not fully understand why the different types of hair growth have Straight Hair, Curly Hair, Wavy Hair, Greasy Hair or Dry Hair. This is probably determined by several factors, which may vary in their importance during life. This is why some curly-headed children have straight hair later in life, and vice versa. These factors include:

• The way the large bundles of keratin are arranged within each hair shaft

• The position of the hair bulb in the hair follicle - in African hair the bulb may lie to the side of the follicle, and so the hair shaft grows out of the follicle at an acute angle

• Irregular growth in the hair bulb - if it varies slightly to one side or the other the hair may grow wavy

• The shape of the hair follicle, whether it is straight or curved

• The number of twists per unit length

All hair, even the apparently perfectly straight hair of Asian people, twists as it grows. The number of twists in a given length of hair determine how curly it is: the more twists there are, the curlier it will be. Some African hair has 12 times as many twists per centimetre as Caucasian hair.
In Asian people the keratin bundles in the hair are all straight. The hair shaft tends to be thick, and almost completely round.

The keratin bundles in the hair of Caucasoid people are a mixture: most are straight, some are wavy. The proportions of the two types vary a lot. The hair shaft is usually oval in shape.

The tightly curled hair of African people twists much more frequently than in the other groups. The hair shafts are markedly oval in shape, with definite edges. The cuticle is sharply kinked at the edges, and is especially easily damaged at these points. This curious shape is the reason for the vulnerability of African hair to all forms of physical and chemical trauma, and its consequent need for extreme care in handling and very thorough conditioning.

Straight hair sometimes becomes quite wavy when damp, and wavy hair may become straight when thoroughly doused with water - in a swimming pool, for instance. This is because in these conditions great numbers of hydrogen bonds have been broken. The effect is very temporary, and the hair recovers on drying

Asian Hair & Caucasoid Hair & African Hair

Asian Hair people are from the Orient, for example from China and Japan. Their hair is very straight, and always black in color.

The Caucasoid group is the most 'varied' of the three racial groups. Modern Caucasoids are very varied, even though they are descended from the same group of ancestors. They range from the fair-skinned people of north-west Europe to the widely varying peoples of the Indian subcontinent.

Caucasoid Hair may be either wavy or straight, and the diameter varies widely too. The color ranges from black to a pale blond that is almost white, including just about every possible shade in between.

African people originated in Africa. African hair is black and tightly curled. It tends to be woolly and dry, and is extremely easily damaged by heat or chemicals.

Different Types of Hair

The range of different types of hair is enormous, ranging from tight wiry curls to ruler-straight. The color and shape of hair vary too. What accounts for these differences?

The type of hair you have is inherited from your parents. We may look back further, and say that it is determined by the part of the world in which your ancestors originated. It all depends on the race, or mixture of races, from which they came.

In the very earliest days of human evolution, three basic racial groups of people seem to have existed on this planet. These spread out across the world and became mixed together. They are especially well mixed in countries where there has been massive immigration, such as the U.S.A. over the last few hundred years.

Scientists have identified three basic types of hair in today's human population, and have related them to these three early races: Asian, Caucasoid and African. The three types of hair not only look quite different, but the differences in their responses to physical and chemical damage can be remarkable.

Hair Texture

Much of the attraction of a beautiful head of hair lies in its texture, or feel. The texture of hair depends on several things.

The first is the average diameter of the individual hairs. We have seen that these vary widely. The larger the hair diameter, the coarser it will feel.

Secondly, different people's hair naturally feels different: some hard and others soft, some silky and others wiry. The reasons underlying these differences are still a matter for scientists to argue over.Thirdly, the texture is affected by the degree of weathering of the hair.

Finally, hair texture is affected by what has been put on it. Repeated lavish applications of hair spray gives hair a different feel from that of hair that has been freshly washed and conditioned. Conditioners make hair feel soft and smooth. Conditioners that contain silicones even give a slightly different feel from those that don't (most manufacturers do put silicones into conditioners nowadays, however, as they protect the hair cuticle). Contrary to popular belief, this altered feel is not a sign of build-up.

Hair Diameter & Hair Porosity

The elastic properties of both wet and dry hair are related to the diameter of the hair shaft. The thicker the hair, the more it will tend to resist stretching

In a normal, undamaged hair shaft, very little water can get either into or out of the cortex. This is because the cuticle covering the cortex is intact, and is then almost (but not quite) waterproof. Shampoos do not damage the cuticle. When hair is permed or tinted, however, the chemicals have to penetrate the cortex in order to react with the keratin inside it. Increasing the temperature, or applying an alkaline lotion, separates the scales of the cuticle enough to allow the chemicals to pass through. After the processing is finished the scales gradually close up again.

But if hair is processed too many times the cuticle scales may never return to their original tightness and the protection they once offered is lost. The cuticle can also be damaged in the same way by too much blow drying, curling irons that are too hot, and the effects of wind and sun. The hair becomes increasingly porous, and water can then pass in and out of the cortex.

Over-porous hair is dry, and tends to develop split ends. The damaged cuticle is fragile, and the damage worsens as time goes by. The greater the damage, the more the cortex swells with water whenever the hair is washed, but the more water it loses when it dries. The repeated wetting and drying of the cortex gradually weakens the hair.

Hair Moisture

The moisture content of hair is greater when the atmosphere is moist and humid, and less when the air is dry.

The reason why hair 'collapses' in hot, humid atmospheres is summed up by:
heat and humidity -> more moisture
-> less static electricity
-> collapse
In dry conditions:
heat and dryness -> less moisture
-> more static electricity
-> more volume (body)

When hair is wet the cortex swells and the edges of the cuticle scales tend to lift. The hair surface temporarily loses its smoothness.There is therefore more friction when wet hair is rubbed than when it is dry. This is what can lead to matting and tangles developing during over-vigorous shampooing (there is not greater static charge on wet hair than on dry).

These tangles are one of the reasons why many children hate having their hair washed, and the problem is easy to avoid.

Hair Static Electricity

When dry hair is rubbed, as it is whenever it is brushed or combed, static electric charge builds up on the hairs. This is especially noticeable in hot, dry weather. The charges tend to push each other apart, and as a result charged hairs can never lie smoothly against each other. The result is 'fly away' hair, which stands out from the head and looks unmanageable.

Conditioners, and shampoos with high levels of conditioning agents in them, leave the surfaces of the hair smooth. There is therefore less friction when the hairs are rubbed: hence less static electricity builds up on them, and 'fly away' is reduced

Hair Elasticity

This is one of the most important properties of hair. Because of its elasticity, hair can resist forces that could change its shape, its volume or its length. Its elasticity lets it spring back to its original form without damage.

When healthy hair is wetted and stretched, it can increase in length by up to 30% and still return to its original length when it is dried. Stretching it more than this will tend to damage it, however, leading to permanent lengthening and even breaking.

The elasticity of hair depends on the long keratin fibres in the cortex. Chemical treatments of hair such as perming and bleaching can alter the cortex after repeated damage, and change the hair's elasticity. Hair with poor elasticity will stretch only to a limited extent. It will not curl, it will break easily when it is groomed and it cannot be permed satisfactorily.Both natural sunlight and artificial ultraviolet light break down chemicals in the hair and damage its elasticity in the same way that bleaching does, though to a much lesser degree.

A stylist must always examine the elasticity of a client's hair before deciding on any chemical procedure.

Physical Properties of Hair

Hair can be stretched, bent and curled. It can absorb moisture or lose it. Its behaviour can alter when it is wetted or when it is brushed. We look at the special properties of hair, such as its elasticity, porosity and texture.

Understanding these properties is important for all of us as we cope with our hair under different circumstances. It is especially important for the hair stylist who has to decide on styles and to suggest continuing hair care regimes for clients.

Closer Hair Check

Hair stylists and technicians examine the whole head of hair as part of their everyday practice. Matters to note include racial type, hair length and hair thickness, and if there is evidence of weathering, of previous cosmetic treatments such as perming and tinting and of accumulated hair spray.
A closer examination of the roots under a good light usually indicates the real state of the hair. The first centimetre or two of growth may look very different from the rest. This could indicate a change in the treatment that the hair has received, perhaps to a persistently harsh regime.

Next comes a look at the individual hair shafts with the naked eye. This may not reveal much, unless there is unusually serious damage. In very long hair that has weathered, the end may look a different color from the rest, or perhaps less glossy. This is almost certainly the onset of split ends.

Under the microscope, however, a very different picture may emerge. Hair scientists use both ordinary microscopes and electron microscopes to examine hair in the laboratory. These allow them to understand what happens to hair when it is heated, permed, tinted and so forth. You will find examples of what can be seen under both kinds of microscope throughout this book.

Loose Hair

Many people worry because they often find loose hairs on their clothes, or after shampooing, and they become terrified in case they may lose some or most of their hair.

If you pull the hair lightly with your hand, you may well find that a few hairs do come out. These are almost certainly hairs that are ready to fall anyway - telogen hairs. You can confirm this by looking at the roots in a good light. A telogen follicle root is a little hard, white bead. Brushed-out hairs all have this kind of root.

On the other hand, the root of a hair that is pulled out is fat, soft to the touch and sticky - it will stick to your hand, because it still carries fluid from the follicle. And pulling it out hurts! This is an anagen hair, one which was not ready to be shed.

Hair Check

From time to time doctors, scientists, hair stylists and technicians are all asked, for different reasons, to examine someone's hair. All of them need to know the right methods to use, and to understand the hair growth cycle and the cosmetic treatments and weathering processes that affect the hair's appearance

Hairlines

Forehead hairlines are determined genetically. The hairline that you were born with may well be the one you ultimately have in your adult life. Nearly all women keep their frontal line unchanged from childhood to old age, although some women's hairlines may seem to recede because their hair gets thinner. About half of all men may expect the hairline to recede to some extent, however.

Hair Stream

A hair does not grow straight up out of the skin, but leaves the follicle at a definite and predetermined angle. This angle determines the direction along which the hair will lie, and determines the patterns or streams that the hairs make on the head. Often the streams spiral outwards from a central point (or points) on the crown of the head. Usually these spirals, or 'whorls', run in a clockwise direction.

The classical 'cowlick', seen in around 7% of children, is due to a particular hair stream on the forehead. Unruly hair in children may be the result of scalp hair patterning. Another possible reason is an unusual structure of the hair shaft.

Hair Growth in Puberty

At puberty the immature vellus-like hairs on our bodies can change to terminal hairs. This change results from the dramatic rise in androgen levels at that time. It is especially noticeable in young men. Young women who suffer from the condition of anorexia nervosa, however, stop having periods and produce very little oestrogen: their natural androgens tend to thicken their fine vellus-like hairs in the same way.

The effects of androgens continue long after puberty. Some areas of the skin respond to these hormones more vigorously than others do, and at different times of life. Pubic and armpit hair begins to grow at or soon after puberty. Most men's beards do not grow strongly until the owners reach their thirties. The growth of chest hair reaches a peak even later, and hair in the nose and ears grows most in late middle age.

Scalp Hair

The hair of the scalp is, however, most sensitive to the effects of male hormones (androgens), which are in the blood of people of both sexes (only in different proportions in men and women). Androgens are the most important factor regulating hair growth, and also the thickness of the hair shaft. Female hormones (oestrogens), which both sexes have too, slow down hair growth during the growing period but also make that period longer. Many women notice a difference in their hair growth during pregnancy. At this time women have vast amounts of oestrogen in their blood, far outweighing their male hormones. It is the balance between the male and female hormones which decides the growth of the hair.

Vitamins for hair growth

Some Vitamens may be particularly important for hair growth. For example, some people who lack zinc in their diet produce only fine, sparse hairs and even lose their hair. Vitamin B, also known as panthenol, plays a part in hair growth. It also improves the physical properties (elasticity, strength and gloss) of the hair shaft.

The hair cycle for each individual hair is influenced by the levels of various hormones in the blood. Thyroid hormone speeds up growth in resting hair follicles. Steroids taken by mouth slow it down, though steroids inhaled for the treatment of asthma do not affect hair growth.

Hair Growth | What controls Hair Growth

No one can answer this question with certainty. What we do know is that it takes a lot to stop hair growing!
General health and nutritional factors are increasingly believed to be important for healthy hair growth. We do know that serious anaemia affects hair growth. So too does starvation: people who go on a crash diet may start to lose their hair some six to ten weeks later. Many alcoholics have poor hair growth or even hair loss because their way of life tends to lead to malnutrition.

Hair Length

How long anagen lasts is determined genetically, and varies between the sexes and from one person to another. It is the length of this time that decides how long the hair will grow before it falls out. Anagen lasts between three and seven years in most people.

• As we have seen, a hair grows at a rate of about 1centimetre a month.

• After one year it will be 12 cm long. After five years it will be 60 cm long.

• Waist-length hair is 80-90 cm long, and will have taken about seven years to grow.

• Shoulder-length hair will have taken only about three years. Thus only people with long anagen times can expect to grow their hair down to the waist.

As people grow older the period of anagen shortens. For example, the hair of someone with a five-year anagen can grow to a length of 60 cm before it enters the shedding phase. If their anagen period drops to three years as they age, their hair will then grow only to shoulder length before it falls out or is brushed out. So when a scanty-haired elderly lady boasts that when she was a girl she could sit on her hair, she may very well be telling you the truth!

Telogen (The Shedding Phase)

The telogen phase lasts for three or four months. This is the time at which a new hair begins to grow from the hair follicle. As it grows upwards the old hair will be shed naturally or may be pulled out, which happens easily and painlessly with telogen hairs. These are the hairs that come out when you shampoo or brush your hair.
Shedding is part of the normal process of the replacement of old hair with new. At any one time, around one in ten of the follicles on an individual's head are in the shedding phase.

The new hair emerges from the same opening at the surface of the skin as the old one, and the hair cycle begins again.

Catagen (The Intermediate Phase)

The anagen phase is followed by a short resting phase. This catagen phase lasts for between two and four weeks in the human scalp. No pigment is made during that time, and the follicle stops producing hair. The base of the follicle moves upwards towards the surface of the skin.

Anagen (The Growing Phase)

The anagen phase of a new hair starts at the moment it begins to grow. At that time there is very active growth in the hair bulb. This usually lasts for some years, generally between three and seven, without interruption. Since human hairs grow at a rate of roughly 1 centimetre a month, hairs can grow to a length of a metre or so.
As we have seen, hair may grow more quickly in winter than in summer. Hair growth varies with the season as a result of a change in the difference between hair follicles in the growing and shedding phases.

Pigment (melanin) is made in the hair bulb throughout this phase of the hair cycle. Less pigment is made in the hair of older people. This is why white hairs start to appear, even though the hair itself may still be growing strongly.

In some older people the hair cycle becomes shorter, the follicles gradually give up producing long, strong hair, and the hairs become thinner and shorter. The result may be a general thinning of the hair, or even a degree of baldness

Stages of the Hair Cycle

Between starting to grow and falling out years later, each hair passes through three distinct stages. These are so important that they have been given special names:

• Anagen (the growing phase)

• Catagen (the intermediate phase)

• Telogen (the shedding phase)

We shall look at these three stages in turn.

The Hair Growth Cycle

Each individual hair is formed inside a hair bulb deep in a hair follicle. The follicle is a tiny but powerful factory, which throughout many people's lifetime hardly ever stops working. From a baby's birth for many decades, as much as a century in some people, the follicle continues to produce hairs. Each hair grows for many years: during this time it will be shampooed, conditioned, cut, blown dry, exposed to sun and wind, colored or bleached or permed. None of these treatments affects the growth of the hair in the hair bulb, even though some may seriously damage the hair shaft. Finally the hair spontaneously falls out. The follicle rests for a little while, and then starts to produce yet another new hair. This is the hair cycle.

You need to know about the hair cycle in order to understand many of the problems people have with their hair. These can range from the sudden appearance of hairless patches to complete baldness in men, and sometimes in women too.

Hair Dimensions

Hair Dimensions vary from person to person.People describe their hair as being thick or thin, coarse or fine. What they are usually talking about is the amount of coverage their hair gives to the head. This coverage depends on two things: how many hairs there are, and the thickness (diameter) of each hair shaft.

People vary a lot in how many hairs they have, and also in how closely together they grow. The 'average' person has around 100,000 hairs, but people with very dense hair may have as many as 150,000.

The Hair Shaft Diameter varies too. Hair Shaft Diameter is usually around 57-90 µm in Europeans. This is much less than in Asians, in whom it can be 120 µm. (These are general figures, representing a wide range of values.)
Hair that is both dense and thick looks completely different from that of someone who has fewer and finer hairs

How Hair Gets its Shape

The shape of a hair depends on several factors, including the shape of the hair follicle and its opening; these vary from one person to another and also between races. As keratin is hardening it is compressed into the shape of the hair follicle. The hair is then held in shape by the pattern of the chemical bonds within it. Of these, the disulphide bonds are the strongest. They can only be changed by chemical methods such as perming or relaxing.

But within each hair the keratin chains are also linked by bonds of a different kind, called hydrogen bonds. There are far more hydrogen bonds than disulphide linkages. The hydrogen bonds are much weaker than the disulphide linkages and more easily broken, and they give hair its flexibility. Hydrogen bonds are broken apart whenever the hair is wetted, and form again as it dries. When they break the shape of the hair changes. If the wet hair is then wound on to rollers it will form a new shape, and if it is dried on the rollers it will keep this shape.

This is the basis of the setting process. The change in shape is only temporary. It is lost when the hair is dampened, because the new hydrogen bonds are broken again.

Hair Chemistry

Hair is Surprisingly Strong: A single hair can support a load of about 100 grams without breaking. You could even spin rope out of hair!

The keratin protein of the cortex is responsible for this unusual strength. The long keratin molecules in the cortex are compressed to form a regular structure, which is not only strong but also flexible.

Proteins are made up of long chains of amino acids. Each chain takes up a helical or coiled form, rather like a long spring, or the cable of a telephone handset.

Most protein chains are made up of various mixtures of the same 20 or so amino acids. Keratin is unique in that its chains contain high concentrations of a particular amino acid called cystine. The proteins in the matrix of the hair contain the highest levels of cystine.

Every cystine unit contains two cysteine amino acids in different chains which have come to lie near to each other and are linked together by two sulphur atoms, forming a very strong chemical bond known as a disulphide linkage. Many disulphide bonds form down the length of the keratin chains, joining them together like the rungs of a ladder.
The disulphide bond is one of the strongest bonds known anywhere in nature. This cross-linking by disulphide linkages between the keratin chains accounts for much of the strength of hair.

Structure of Hair Shaft

Your smooth, glossy hairs have a more complicated structure than you might think. Each one can be compared to a tree: all its moisture lies in its centre, behind a tough outer layer of protective bark. If the 'bark' of the hair is well looked after the whole hair remains in good condition. If the 'bark' is stripped off to expose the centre the hair may break.

The centre part of the hair, called the cortex, makes up most of the hair shaft. It is the cortex that gives hair its special qualities such as elasticity and curl. The cortex is packed with strands of keratin, lying along the length of the hair. These keratin fibres are made of the low-sulphur keratins, and are compressed into bundles of larger fibres. These are held together by a mass of sulphur-rich keratins, the matrix. The fibre-matrix combination is extremely strong and resists stretching and other strains such as twisting, much as does the glass fibre-resin mixture from which many boats are built.

The cortex also contains granules of the hair pigment melanin, produced when the hair was growing in its follicle. The granules are of two types: smooth, dark granules which tend to be regularly positioned within the cortex, and lighter granules that are more irregular in shape and which are scattered randomly through the cortex. A hair may contain just one type of granule or a mixture.

In some of the terminal hairs, especially grey (unpigmented) ones, the cortex has a central hollow core, the medulla. There are medullae in the hairs of many animals, and they play a part in the regulation of body temperature. It may be that the presence of this air space in some human hairs is an evolutionary 'throw-back' to a time when our ancestors needed extra heat insulation.
The outer layer of the hair (the 'bark') is called the cuticle. It is made up of between six and ten overlapping layers of long cells. Each of these cells or scales is about 0.3 micrometres thick and around 100 micrometres long, and about 10 micrometres across. (1 micrometre, written 1 µm, is one-millionth part of a metre = one-thousandth part of a millimetre.) The scales lie along the surface of the hair like tiles on a roof, with their free edges directed towards the tip. They cover the hair surface all the way along its length.

If you could look at a hair under a powerful microscope you would see that the scales growing over the youngest part of the hair (the part that grows closest to the scalp) are smooth and unbroken. Further along the hair, you would be able to see that they may have been damaged by cosmetic treatments and by mis­treatment such as over-energetic brushing. Little by little they may break away, a process called weathering.

A healthy cuticle is more than just a protective layer. Much of the shine that makes healthy hair so attractive is due to the cuticle. Intact cuticle cells are smooth and glossy, and reflect light from their surfaces. This, together with the pigment within the cortex, gives hair its characteristic appearance.

Black hair reflects less light than blond hair does. Black hair appears glossier, however, Because the bright bands of reflected light contrast more sharply with the darkness of the rest of the hair.

The Hair Shaft

This is the part of the hair that can be seen above the scalp. It consists mainly of dead cells that have turned into keratins and binding material, together with small amounts of water.

Terminal hairs on the head are lubricated by a natural oil (sebum) produced by the sebaceous glands of the follicles. How much natural oil your glands produce is mostly determined by your genetic inheritance. But in addition boys' and girls' glands tend to produce more oil when levels of their hormones (androgens) are high. In many teenagers, a massive surge in hormone levels leads to raised grease production. This results in a tendency to greasy hair, which many young people know all too well. The good news is that most of them outgrow it

Mid-Follicle Region

In this part of the follicle the actively growing cells die and harden into what we call a hair. As the cells below continue to divide and push upwards, the hair grows upwards too, out of the skin. It now consists of a mixture of different forms of the special hair protein, keratin.

Some of these keratins contain a high level of sulphur, some much less. The sulphur plays an important part in the way the hair behaves, especially when it is given cosmetic treatments. You will find more about this later in the book.

Hair Bulb

The hair bulb lies inside the hair follicle. It is a structure of actively growing cells, which eventually produce the long fine cylinder of a hair.New cells are continuously produced in the lower part of the bulb. As they grow and develop they steadily push the previously formed cells upwards. When the cells reach the upper part of the bulb they begin to change, and they arrange themselves into six cylindrical layers, one inside the other. The inner three layers of cells become the actual hair. The outer three layers become the lining of the hair follicle - the inner root sheath.

Special cells in the hair bulb produce the pigment that colors the hair. The pigment is called melanin, and these cells are known as melanocytes. As the developing hair moves upwards in the follicle the melanin is carried upwards in the inner part of the hair

Hair Follicle

A hair follicle is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is the point from which the hair grows. It is well supplied with minute blood vessels, and the blood passing through them nourishes the growing region. The temperature around the follicle is normal body temperature, and is not affected by cold or hot weather.

The hair of an animal like a cat or a horse grows at different rates depending on the amount of natural light, which varies according to the time of year: it grows more quickly in winter when the days are short.Human hair probably behaves in the same way,growing a little faster in winter than in summer.The hair follicle can be divided into two regions.

Middle Aged Hair and Old Age Hair

Many older people find that their hair continues to grow strongly, and that they have as much hair at 80 as they had at 50. Other people find that their hair gets thinner as they age, and that by the time they are in their 80s only a few wisps remain. Again, this is determined genetically, not by anything they have done to their hair.

Puberty Hair

Before puberty, the scalp carries a mixture of short vellus-like hairs and longer terminal hairs, together with various 'in-between' hairs. After puberty, in both sexes, most of the scalp hairs are terminal hairs. These hairs are thicker in diameter than the childhood hairs, especially in dark-haired people.

At puberty, terminal hairs begin to appear in the armpits, groins and legs, and also (in males) on the chin, chest and forearms. How much body hair you develop is genetically determined (that is, it is inherited from your parents).

Baby Hair

A newly born full-term baby has two types of hair. Terminal hairs grow on the scalp and eyebrows, but nowhere else. All the rest of the hair is vellus hair.

As the baby grows, the hair on the head grows too. There are two periods during which hair grows rapidly on the scalp. In both, the hair growth begins at the forehead and then extends to the back of the neck. When the baby is two or three mdnths old, the first hairs may be shed naturally over an area on the back of the head. This is often mistakenly thought to be due to head rubbing; hairs broken by rubbing may, however, be found on other parts of the head as well.

During the first year of the baby's life, all the hairs on the head grow at the same rate. At that time the head carries an even covering of hair. Then the individual hairs begin to grow independently, at different rates and in different cycles (you will read about hair growth cycles later in this chapter). Growth patterns called 'mosaics' develop.
Many children's hair shows features which are lost in adulthood. These include:

• Unruly hair which sticks straight up

• Atural curls

• Hair without pigment, which darkens as the child grow

Hair Variations

Human hair varies enormously. Different people have hair that differs in color, in length, in diameter, and in its distribution on the body. As we shall see later, some of these factors are influenced by the person's racial type, and some by his or her age.

Managing Hair

The appearance of the hair is the one feature of the body over which humans, unlike other primates, can have direct control. You can change the length, shape, color and style of your hair (including, for men, facial hair) according to the age you wish to appear, and the economic and social status you want to claim.
The style, length and condition of hair all play a part in how we perceive the people we meet.

How much Hair do we have / Hairs on a Human Head

• On average, each person's head carries about 100,000 hair follicles. Some people have as many as 150,000.

• On a baby's head, there are about 1,100 follicles per square centimetre.

• By the age of 25, this number has fallen to about 600, but the number depends on the physical type of the individual.

• Between the ages of 30 and 50, the number drops further, to 250-300. There is only a slight further fall with age.

• Each follicle grows about 20 new hairs in a lifetime. Each new hair grows for several years, and can reach over a metre in length.

• Each hair falls out eventually, and is replaced by a new one.