Cosmetics – Biological Aspects PDF/PPT

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Cosmetics – Biological

Presented by,
M.Pharm II Semester,

Department of Pharmaceutics,
College of Pharmacy, MMC.


• Structure of Skin

• Biological aspects relating to skin problems

– Dry Skin

– Acne

– Pigmentation

– Prickly heat

– Wrinkles

– Body odour

• Structure of hair

• Hair growth cycle

• References





▪ The organs of the integumentary system include the skin and its accessory structure including hair, nails.

• It is the largest organ by surface area and weight.

• Its area is about 2 square meters (22 square feet) and weighs 4.5–5kg (10–11 lb), about 16% of body


• It is 0.5–4 mm thick, thinnest on the eyelids, thickest on the heels.

• We lose almost a kg of skin epithelium a year.


Structure of Skin

▪ The skin has 3 major layers:

▪ The outer, thinner layer is called the epidermis and consists of epithelial tissue.

▪ The inner, thicker layer is called the dermis and consists of connective tissue.

▪ The subcutaneous (subQ) layer (also called the hypodermis) is located underneath the


▪ It is a loose areolar/adipose C.T. that attaches the skin to the underlying tissues and organs.


Structure of Skin


The Epidermis

❖ The epidermis is composed of keratinized stratified

squamous epithelium

which contain four major types

of cells:

▪ Keratinocytes

▪ Melanocytes

▪ Langerhans cells

▪ Merkel cells


❖ The epidermis is composed of four layers in thin skin, and

five layers in thick skin.

▪ The stratum basale or stratum germinativum is the deepest layer.

Continuous cell division occurs here and produces all the other


▪ The stratum spinosum is a layer of 8–10 keratinocytes

▪ The non-dividing cells of the 3rd layer (stratum

granulosum) are filled with granules of keratin.


❖ The stratum lucidum is the 4th layer but is only present in thick skin (the

skin of the fingertips, palms, and soles).

❖ The stratum corneum is outermost, composed of approximately 20 layers

of flat cell-remnants (dead keratinocytes with no cellular organelles filled

with only keratin protein.)

▪ They are continuously shed and replaced by cells from deeper strata.


❖ Keratinization is the process of replacing viable cells in the

stratum basale with more and more of the waxy keratin protein as

cells move from the deepest layer to the surface layer.

▪ Constant friction can stimulate the process and produce a callus

(an even thicker buildup of keratinocytes in the stratum


▪ Dandruff is an excess of keratinized cells shed from the scalp.


The Epidermis


The Dermis

❖ The dermis is composed of connective tissue containing collagen and

elastic fibers.

❖ It contains two regions:

▪ The papillary region lies just below the epidermis and consists of

areolar connective tissue containing thin Collagen and elastic

fibers, dermal papillae (including capillary loops), corpuscles of touch

and free nerve endings.


The Dermis

▪ The reticular region consists of dense irregular

connective tissue containing collagen and elastic fibers,

adipose cells, hair follicles, nerves, sebaceous (oil) glands,

and sudoriferous (sweat) glands.

• Tears or excessive

stretching in this region

cause stretch marks (also

called striae).


The Dermis
❖ Lines of cleavage are “tension lines” in the skin that indicate

the predominant direction of underlying collagen fibers.

▪ Plastic surgeons make their incisions parallel to the

normal cleavage lines in order to minimize scarring.

❖ Epidermal ridges reflect contours of the underlying dermal

papillae and form the basis for fingerprints (and footprints)

▪ Function to increase firmness of grip by increasing



The Subcutaneous layer

❖ The subcutaneous layer is also called the hypodermis, and it
attaches the skin to underlying tissues and organs.

▪ It contains blood vessels and nerves in transit to the more

superficial layers.

▪ It also contains lamellated (pacinian) corpuscles that detect sub

external pressure applied to the skin. Q


Problems Associated
with Skin



• Dry skin is an awkward condition set apart by scaling, tingling, and breaking.

• Dry skin is a condition described as absence of water in the most shallow layer of the skin.

• Dry skin has a low level of sebum and can be prone to sensitivity.

• It usually feels “tight“ and uncomfortable after washing unless some type of moisturizer or skin cream is

• Chapping and cracking are signs of extremely dry, dehydrated skin.

• It looks dull, especially on the cheeks and around the eyes. There may be tiny expression lines on these spots
and at the corners of the mouth



• The oil glands do not supply enough lubrication to the skin. As a result, the skin becomes dehydrated.

• Dry skin could be due to a genetic condition.

• Poor diet. Nutritional deficiencies, especially deficiencies of vitamin A and the B vitamins, can also contribute
to dry skin.

• Environmental factors such as exposure to sun, wind, cold, chemicals, or cosmetics, or excessive bathing with
harsh soaps.

• Conditions such as dermatitis, eczema, psoriasis.

• Ichthyosis Vulgaris

• Allergic Eczema

• Dehydration

• Hypothyroidism



• Xeroderma or xerodermia “dry skin”, is a condition which can safely be treated with

• Cleansing, Moisturizing

• Medicines

• Change in lifestyle

• Humidify during winter

• Applying cool cloths

• Avoiding heat



• Dry skin needs plenty of thorough but gentle cleansing, regular stimulation with massage and
generous quantities of oil and moisture.

• Washing dry skin with soap and water not only removes grime but also the natural oils protecting
the skin.

• A moisturizer increases the water content of the outer layers of the skin and gives it a soft, moist


• Eat a balanced diet that includes vegetables, fruits, grains, seeds, and nuts.

• Drink at least 2 L of water every day to keep the skin well hydrated. Eat foods such as garlic,
onions, eggs, and asparagus that are high in sulfur, which helps to keep the skin smooth and



• Acne, also known as acne vulgaris

• Its an inflammatory skin condition that occurs when oil and dead skin cells block the pore opening,
causing sebum (oil) to build up inside the pore

• It is characterized by blackheads or whiteheads, pimples, oily skin

and possible scarring.

• It primarily affects areas of the skin with a relatively high number

of oil glands



• Stage 1: Clogged Pores. Cells lining pores shed
and mix with excess sebum produced by sebaceous
glands, forming a plug, which leads to clogged pores.

• Stage 2: Bacteria. Accumulated sebum and dead
cells attract propioni bacterium naturally found in
skin, which feeds on oil and multiplies rapidly inside

• Stage 3: Inflammation. This bacterial overgrowth
triggers the natural inflammatory response causing
swelling and redness. This can ultimately lead to
discoloration and scarring.



• Genes

• Hormonal activity, such as occurs during menstrual cycles and puberty

• Infections against anaerobic bacterial species Propionibacterium acnes

• High-glycemic-load diets

• Stress can aggravate the skin by triggering release of androgens and cortisol. These stress
hormones can stimulate an overproduction of oil. When this excess oil mixes with dead skin cells,
it promotes bacterial growth and can cause acne to develop or worsen.

• Acne is caused by the excess production of sebum from skin.

• Several medications like lithium, hydantoin, isoniazid, glucocorticoids, iodides, bromides, and



➢ Too much washing will only irritate the skin further and worsen their acne. Gently washing the face daily
with mild cleanser or soap, pat dry and use appropriate acne treatment

➢ Antibiotics used for mild to moderate inflammatory acne.

• They have activity against P. acnes, act on the surface of the skin to reduce the stimulus for inflammation
of the lesions, inhibit the growth of bacteria and reduce inflammation. Topical antibiotics used in acne
treatment are erythromycin, clindamycin etc.

➢ Benzoyl Peroxide

• Benzoyl peroxide is a topical disinfectant, originally employed as a peeling agent for treating acne .

• Benzoyl peroxide has proven bactericidal activity against P. acnes by releasing free radical oxygen, which
degrades the bacterial proteins

➢ Azelaic Acid

• Azelaic acid is a natural dicarboxylic acid that inhibits protein synthesis of the P.

acnes species .

• It is an ewfwfwe.DcutliovMeix .caogment because it has bacteriostatic, anti-inflammatory, antioxidant.


➢ Use anti-androgen (e.g. oral contraceptive pills) to regulate androgen, to prevent excess sebum
production. This method is only suitable for women.

➢ Some acne scar will remain permanent, so patients should use appropriate acne treatment as soon as


Help clear dead skin

Help clear blackheads

This allows sebum to move freely again

The spots heal


Skin color is due to a pigment, called melanin. Melanin is produced by melanocytes ( cells present in the

basal layer of the epidermis) and is responsible for the coloration of skin, hair and eyes.

• Melanin is synthesized by melanocytes within melanosomes and transferred to keratinocytes.

Pigmentation disorders are disturbances of human skin color, either loss or reduction, which may be

related to

➢ loss of melanocytes or the

➢ inability of melanocytes to produce melanin or

➢ transport melanosomes correctly.

•Pigmentation is the coloring of an individual’s skin. The color of skin appears normal when a person is


• A person’s skin may change color and grow darker (hyperpigmentation) or lighter (hypopigmentation)

because of illness and/ injury.


• Hyperpigmentation

It is a darkening of area of skin or nails caused by increased melanin. Exposure to sunlight is
a major cause of hyperpigmentation.

• Hypopigmentation

It is the loss of skin colour which is caused by melanin depletion.

• Vitiligo

It is an auto immune disease in which there is a appearance of an smooth white patches on
the skin occur all over the body.

• Albinism

It is a rare inherited disorder which is caused by absence of an enzyme that produces
melanin. Pigmentation is completely lost as a result in eyes, skin and hair.

• Depigmentation-lightening of skin or loss of pigments.


• Sun damage

• Certain medications

• Skin injuries related to acne vulgaris

• Excess production of melanin

• Hormonal changes due to pregnancy

• Presence of endocrine disease like Addison’s disease

• Inflammation

• Excess exposure to sunlight.



• HQ affects not only the formation melanisation and degradation of melanosomes but it also
affects the membranous structures of melanocytes and eventually causes necrosis of whole

• HQ concentration 2-5% applied once daily.

2.Azelaic acid

• Azelaic acid is a naturally occurring non phenolic, saturated, 9 carbon dicarboxylic acid that
competitively inhibit tyrosinase.

• Azelaic acid was initially developed for the treatment of acne but it has effect on tyrosinase, it
has also been used to treat melasma, lentigo maligna and other disorders of


• It is a beta –D-glucopyranoside derivative of HQ naturally occurring plant product. Used in
the hyperpigmentary products.


4.Glycolic acid

Glycolic acid is an α hydroxy acid that is usually combined with other agents at a

concentration of 5-10% for its skin lightening property.


• The biologically active form of niacin(vit-B3) can reduce pigmentation by reversibly the

transfer of melanosomes from the melanocytes to the keratinocytes.

6.Liquorice extract

• Liquorice is the root of glycerrhiza glabra from which a some what sweet flavour can be

extracted the main component of the hydrophobic attraction of liquorice extract is

glabridin which has an effect on skin.



• Preparation of base

Water in oil(w/o) cream was prepared by the addition of aqueous phase to the oily
phase with continuous agitation.

To prepare base: oily phase that consisted of paraffin oil, bees wax, coconut oil and
surfactants (cetomacrogol 1000 and cetostearyl alcohol) is heated upto 75°c.

Aqueous phase consisting of glycerine and water heated to the same temperature.

• Preparation of formulation

The formulation was also prepared by same method the only difference is the
addition of glycorrhiza glabra extract that is added in a aqueous phase consisting of
glycerine and water.

Each formulation consists of preservative as a propyl paraben 0.02%w/w and
methyl paraben 0.1%w/w. The formulation were neutralized by triethanolamine to
pH=5.5 at 25°c.



• Bleaching agents

• Chemical peels

• Intense pulsed light

• Microdermabasion

• Physician formulas

• Laser resurfacing

• Home remedies/ natural treatments



• Wrinkles are the lines and creases that form in your skin.

• A wrinkles also known as rhytide, is a fold, ridge or a crease in the skin.

• Skin wrinkles typically appear as a result of ageing process such as glycation,
habitual sleeping positions, loss of body mass, or as a result of prolonged
immersion in a water.

• It is specially noticeable around your eyes, mouth and neck some wrinkles can
become deep crevices or a furrows


• Age

As you get older, your skin naturally becomes less elastic and more fragile. Decrease
production of natural oil dries your skin and make it appear more wrinkled.

Fat in the deeper layers of your skin diminishes. These causes loose, saggy skin and more
pronounced lines and crevices.

• Exposure to UV light

UV radiation which speeds the natural ageing process, is the primary cause of early

Exposure to UV light breaks down your skins connective tissue collagen and elastic fibres,
which lie in the deeper layer of skin (dermis) and results in skin loses strength and flexibility

Skin begins to sag and wrinkle prematurely.

• Smoking

Smoking can accelerate the normal ageing process of our skin, contributing to wrinkles. This
may be due to changes in the blood supply to your skin


• Repeated facial expression

The facial movements and expressions such as squinting or smiling leads to fine lines and

• Poor hydration

It also one of the causes of wrinkles


• Protect your skin from the sun

• Use products with built in sunscreen

• Use moisturizers

• Don’t smoke

• Eat a healthy diet


• Fillers

The fillers is an biological or syntactical mean to inject in hypoderm or in dermal tissue, to
enhance a limited area of the body (usually face) for aesthetic purpose

• Peelings

Peeling is a medical treatment consisting in a micro-abrasion of epidermis or the superficial and
medium derma, by means of chemical or physical agents.

The peels used in these treatments are pyruvic acid ,salicylic acid, retinoic acid, trichloro acetic
acid at 10-20%

• Botulinum toxin

Botulinum toxin injection for treatment of facial wrinkles is one of the most common entry
procedure for clinicians seeking to incorporate aesthetic treatments into their practice.

It is a potent neurotoxin that inhibits release of acetylcholine at the neuromuscular junction.

• Lasers

They are indicated for treatments of aesthetic lesions, for resurfacing, for non-ablative
rejuventing and for hair removal. The used lasers are the CO2 laser.


• Other treatments-dermabrasion, surgery, ultrasound therapy

• Topical retinoids: derived from vit A, retinoids- such as tretinoin (renova, retin A) and
tazarotene(avage, tazorac) –that you apply to your skin may reduce fine wrinkles,
splotches and skin roughness.

• Nonprescription wrinkle creams

The effectiveness of antiwrinkle creams depends in part on the active ingredients. retinol,
antioxidants and some peptides may result in slight to modest improvements in wrinkles.


• It is also known as miliaria and heat rash.

• A heat rash occurs when sweat ducts become clogged and the sweat can’t get to the surface
of the skin. It becomes trapped beneath the skin surface causing a mild inflammation of

• The common symptoms of heat rash are red bumps on the skin, and an itchy or prickly
feeling to the skin.

Types of heat rashes






1. Body odor is the perceived unpleasant smell our bodies can give off when bacteria that live on

the skin break down sweat into acids.

2. Body odor usually becomes evident if measures are not taken when a human reaches puberty.

People who are obese, those who regularly eat spicy foods, as well as individuals with certain

medical conditions, such as diabetes, are more susceptible to having body odor.

3. People who sweat too much, such as those with hyperhidrosis, may also be susceptible to body

odor. However, often the salt level of their sweat is too high for the bacteria to break down. It

depends on where the excess sweating is occurring and which type of sweat glands are involved.

4.Sweat itself is virtually odorless to humans. It is the rapid multiplication of bacteria in the

presence of sweat and their breaking down of sweat into acids that eventually causes the

unpleasant smell.



1. Body odor is caused by bacteria breaking down sweat and is largely linked to the

apocrine glands. Most body odor comes from these.

2. These glands are found in the breasts, genital area, eyelids, armpits, and ear. In the ear,

they help form earwax. Apocrine glands in the skin and the eyelids are sweat glands.

3. Most of the apocrine glands in the skin are located in the groin, arm pits. In the skin,

they usually have an odor.

4. The apocrine glands are mainly responsible for body odor because the sweat they

produce is high in protein, which bacteria can break down easily.


Wash daily with warm water: Have a shower or bath at least once a day. since warm water

helps kill off bacteria that are present on the skin. If the weather is exceptionally hot, consider

bathing more often than once a day.

Clothing: Natural fibers allow your skin to breathe, resulting in better evaporation of sweat.

Natural-made fibers include wool, silk or cotton.

Avoid spicy foods: Curry, garlic, and other spicy foods have the potential to make some

people’s sweat more pungent. Some experts believe a diet high in red meat may also raise the risk

of developing more rapid body odor.

Aluminum chloride: This substance is usually the main active ingredient in antiperspirants. If

your body does not respond to the home remedies mentioned above, talk to a pharmacist or your

doctor about a suitable product containing aluminum chloride. Follow the instructions given to

you carefully.


Antiperspirant : these are personal hygiene products designed to control sweating and body

odour safely and effectively. They are readily available on the market as sprays (aerosol) ,sticks,

creams and roll-ons.

Deodorant : these are used to eliminate bad odour which is generally caused by sweating .They

are applied locally on the surface of the body

Botulinum toxin: This is a toxin produced by Clostridium botulinum; it is the most poisonous

biological substance known. However, very small and controlled doses are today being used in

various fields of medicine. A relatively new treatment is available for individuals who sweat

excessively under the arms.

The individual is given approximately 12 injections of botulinum toxin in the armpits – a procedure

that should not last more than 45 minutes. The toxin blocks the signals from the brain to the sweat

glands, resulting in less sweating in the targeted area. One treatment can last from two to eight






• Hair follicles are formed early in development of the fetus, with eyebrow, upper lip, and chin follicles

present at week 9 and the full complement of follicles present by week 22.

• At this time, the total body number of 5 million follicles is present, with 1 million on the head, of which

100,000 are on the scalp

• No additional follicles are formed during life.

• As body size increases, the number of hair follicles per unit area decreases.

• The average density of hair follicles in the new born is 1135 per cm2, drops to 795 per cm2 at the end of the

first year, and decreases to 615 per cm2 by the end of the third decade.

• Continued decrease in hair follicle density occur on the scalp with balding.


Structure of Hair Follicle

• The hair grows from follicles which resemble stocking-like invaginations of the epithelium enclosing an

area of dermis known as the dermal papillae .

• The area of active cell division, the living area of the hair, is formed around the dermal papillae and is

known as the bulb, where cell division occurs every 23 to 72 hr.

• This epidermal layer forms the outer root sheath (ORS), which is the outermost of a number of concentric

cell layers forming the complex structure of the human hair follicle.

• The next layer is the inner root sheath (IRS), which actually consists of three layers, that is, the Henle, the

Huxley, and the IRS cuticle layers, the latter being in direct contact with the cuticle cells of the growing

hair fibre.




• The hair is a made up of water insoluble protein known as Keratin, which as

a protein consists of many amino acids as its primary units.

• The physical shape of hair has mainly three parts,






• The cuticles are the protective layers and make the outer surface of hair.

• There are 6 to 10 layers of cuticles glued together with cell membrane complex

• There are only two cuticle layers on the crimped side of the coily hair

• The architecture of cuticle layers is shown in following figure .


The architecture of Hair Cuticles

• The diameter of hair fiber is
around 80 microns (µm).

• Fine hair has a diameter range of
50 to 60 microns

• Medium hair has a diameter of 61
to 80 microns.

• Coarse thick hair has a diameter
of 81 to 100 microns.


• Each cuticle layer is about 60µ long and 0.5µ thick.

• The length of overlap area of one cuticle layer over the other cuticle layer is about 5µ.

• The excessively curly hair has varying numbers of cuticle layers along the hair shaft. Only one to two

cuticle layers are found on spots where hair is thin/flat along the minor axis and 6 to 10 layers along

major axis where hair is thick.

• The cuticles are rich in amino acid (cystine) and fatty acids.

• The outer most part of the cuticle of hair is composed of fatty acid called 18-MEA (18-

methyleicosanoic Acid) also known as F-Layer. All of the 18-MEA is present in the upper most

surface of the cuticle.


Structure of Cuticle
The structure of the cuticle itself is quite complex and
is further subdivided in four parts, such as

• Epicuticle

• A – layer

• Exocuticle

• Endocuticle



• The epicuticle is a very thin membrane that covers the cuticle as an outermost layer.

• It is about 5 to 7(nm) thick.

• It is very hydrophobic in nature.

• The F-Layer (18 – MEA) is not very resistant to alkalies, oxidizing agents, and proteolytic agents and on

prolonged exposure, significant chemical changes take place in the epicuticle layer

• This renders hair fibers more porous while increasing the inter fiber friction.

A Layer

• The ‘A’ layer exists below the epicuticle layer.

• The ‘A’ layer and exocuticle layer form about two-thirds of the scale structure of a cuticle.


• They are very rich in cystine contents and contains about 35 % of cystine.

• The ‘A’ layer resists the attack from physical forces such as repetitive combing and brushing during

grooming and blow drying; and chemical forces such as alkalies, reducing agents, oxidizing agents, and

proteolytic enzymes.


• The sub layer below the ‘A’ layer is called exocuticles

• It has about 15 % of cystine contents.

• The exocuticles do not have fibrillar structure.

• The ‘A’ layer is actually a part of the exocuticles that are divided into ‘A’ layer and ‘B’ layer, and this ‘B’ layer

is usually termed as exocuticles .



• It lies next to the exocuticle layer and contains low cystine contents of about 3 %.

• It is the weakest component of the cuticle structure, mechanically.

• Due to the very low presence of cystine contents in endocuticle layer, it has a very soft and deformable

structure and swells considerably more in water than exocuticle layers.

• The pronounced projection of cuticles during wet state is because the endocuticle layer swells upon wetting

with water.

• The entanglement of the hair fibers is greater in the wet state and it is due to the extraordinary swelling of


• The endocuticle layer can easily deteriorate from the proteolytic agents and other reactive chemicals such

as alkaliewsw.


• It is inferred that the role of the cuticles is to oppose the penetration of the reactive

and non-reactive chemicals into the cortex of the hair.

Cell Membrane Complex (CMC) of the Cuticles

Each cuticle layer is glued to the next cuticle layer with the help of the material called

intercellular cement or cell membrane complex (CMC) and its intercellular spaces.


• Types of CMC: There are three types of cell membrane complexes.

– The first type of CMC is between just cuticles.

– The second type of CMC is between inner most cuticle layer and the

cortical cells.

– The third CMC is between the cortical cells themselves.

– All of these three CMCs are somewhat different in their compositions.

• The essential role of the CMC between the cuticles is the cohesion of the

one cuticle layer to the other.

• The outer Beta layers are 5nm thick and are comprised of lipids. The

central Delta layer is 15nm thick.



• The central core of the hair is called cortex.

• It is covered by the cuticle and it occupies 75 to 80% of the hair volume .

• It is mechanically the most important part of the hair and largely responsible for the elasticity and tensile

strength of hair.


Cortical Cells
• The cortex is primarily made up of cortical cells.

• They are proteinaceous cells of elongated shape of regular and
irregular cross-sections.

• The diameter of these cells is between 2 to 5 µm.

• The length of the cortical cell is around 100µm.

• These cells are spindle shaped, various sizes, and aligned
along the main axis of the fibers.

• There are two types of cortical cells: para cortical cells and
ortho cortical cells.

• The para cortical cells possess a uniform spindle shape while
ortho cortical cells are non-uniform in shape.


• Each cortical cell is separated from the

neighbouring cortical cell and they are glued

together by the cortical-cortical cell membrane

complex, which is approximately 25nm thick.

• The inner most cuticle layer and the outermost

cortical cells are glued together with the cuticle-

cortex CMC.

• The cortical cells are glued together with cortical-

cortical CMC into a solid mass, as shown in Figure.


• Macro fibrils: The cortical cells consist of macro fibrils that

are separated by a thin membrane in the cortical cell. These

membranes also contain the pigment of the hair known as

melanin, which is variably dispersed in the membrane.

• The macro fibrils are embedded in the cortical cells as units

and are separated by inter-macro fibrilar material or matrix

in the cortical cells.

• The macro fibrils are rod like structures, with a length of few

µm and a diameter of 0.1 to 0.4 µm.

• These keratinized macro fibril units are oriented

longitudinally within the cells, thereby, providing a very

strong fibewrw-mw.DautlorMiixx. ccomomposite, as shown in Figure.


• Microfibrils/Intermediate Filaments (IF):

The macro fibril contains many microfibrils also

know as intermediate filaments.

• Macro fibril consists of long uniform filaments

known as Intermediate Fibrils (IF) that are

oriented parallel to the axis of the hair fiber.

• Each IF is about 8 nm or 0.008 µm in diameter

and is about 11 nm apart from another IF.

• The IFs contain very organized helical material

protein chains twisted together like a rope.


• The Matrix: The microfibrils/Intermediate

filaments are embedded in the matrix of macro

fibrils and cortical cells.

• Its major role is to hold together microfibrils

(Intermediate Filaments) in a stationary stable state

with some freedom of movement also known as the

elasticity of hair fibers.

• The degree of loss in tensile strength of hair fibers

during chemical treatments, corresponds to the

extent of damage to the matrix.

• If the microfibrils and the protein matrix are

denatured partially or fully, the hair fiber looses its

mechanical properties (tensile strength and

elasticity) relatively.


• Protofibrils: One microfibril/Intermediate

filament consists of 8 protofibrils and each

protofibril consists of four protofilaments. The

structure of a protofibril is shown in Figure.


• Protofilaments: The four protofilaments are

present in each protofibril and they are the – helical

formations to form a dimmer.

• Then two dimmers aggregate to form a tetramer. The

tetramer is also known as protofilament.

• The diameter of a protofilament is 2.8 nm or 0.0028

mm. The structure of a protofilament is shown in



• Dimers: The protofilament (tetramer) is

comprised of two dimers and the

structure of a dimer is shown in Figure

• A dimer has two protein chains twisted

together in a special helical pattern.

• There are 16 dimers in a

microfibril/intermediate filament (IF).


• The combination of these elements produces a composite structure of hair fiber,
as shown in Figure


• It is the empty intermittent space that exists in the middle of the fiber and is called medulla.

• The function of the medulla is not well known and very little research is conducted on the chemistry and

other properties of medulla.

• It is believed to contribute in higher volume/ body to the hair.

• The medulla may provide thermo-regulatory properties to hair with regard to the airspaces within the


• The hair fiber that is fine in texture seems to have very little medulla or no medulla and tends to have very

little body.

• The hair fiber that is coarse in texture seems to have higher degree of medulla and consequently has lots of


• Thereforew,w wth.Deul mof the medulla determines the degree of the body (volume) of the hair fiber


• All hair follicles undergo cyclic growth activity.

• An active phase, anagen, in which a hair is produced alternates with a resting period, telogen, in which

the fully formed club hair remains anchored in the follicle by its expanded base and the dermal papilla

lies free of the epidermal matrix, which is reduced to a small, quiescent secondary germ.

• Between anagen and telogen is a relatively short transition phase, known as catagen, in which the

newly formed club hair moves toward the skin surface.

• The follicle becomes active again at the end of telogen by a downgrowth of the secondary germ to

reinvest the dermal papilla, so that the matrix becomes reconstituted and a new hair starts to form.

• In this effect the follicle re-enacts its embryonic development.

• Ultimately the old club hair is shed. All hairs thus reach a terminal length which is determined mainly

by the duration of anagen and partly by the rate of growth.



• The growth rate of human hair has been determined by direct measurement of marked hairs in situ, by

shaving or clipping at selected intervals, and by pulse labelling 35S cystine and autoradiography.

• The average growth per 24 hours has been stated to range from about 0.21 mm on the female thigh to

0.38 mm on the male chin.

• Though scalp hair appears to grow faster in women than in men, before puberty the rate is greater in boys

than in girls.

• In both sexes the growth rate is highest between the ages of 50 and 69 years.

• The growth rate remains constant in any follicle

• Daily variations in temperature have no effect on hair growth, and it is generally agreed that shaving does

not alter the rate of hair growth.



• There is sample experimental and clinical evidence that hormones influence hair growth,

although in a poorly understood and complicated way.

• The follicular cycle is disturbed by the high level of oestrogen during late

pregnancy, apparently leading to postpartum alopecia.

• The successive growth of pubic and axillary hair in both sexes at puberty and the growth of

the male beard are brought about by rising levels of androgens.

• Paradoxically, androgens are also prerequisites for the development of male pattern



• Certain vitamins, particularly some of the B complex, are necessary for normal hair growth

and keratinization of the epidermis.

• It has been shown that vitamin A inhibits the differentiation of the stratified squamous

epithelium. Thus hyperkeratotic papular dermatosis is a symptom of vitamin A deficiency, and

an excess of vitamin A cause hair loss.

• Protein deficiency causes kwashiorkor and has serious consequences for hair growth. The hair

becomes sparse, thin, and brittle, and loses its pigment.

• The changes in the hair reflect considerable alterations in the follicular cycle, resulting in a

considerably reduced proportion of the follicles in anagen (26% for children with kwashiorkor

vs. 66% for healthy children).

• Furthermore, even the anagen follicles are severely atrophied with loss of inner root sheaths

and outer root sheaths.


1. Harry’s Cosmeticology. 8th edition.

References 2. Poucher’sperfumecosmeticsandSoaps,10th edition.

3. Cosmetics – Formulation, Manufacture and quality
control, PP.Sharma,4th edition

4. Handbook of cosmetic science and Technology
A.O.Barel, M.Paye and H.I. Maibach. 3 rd edition

5. Internet source



• Wikepedia