The symbolism of hair is very strong in all peoples and in all times:
- In India, the shorn hair is offered as a sign of humility towards their God.
- Catholic clerics shaved their heads before entering the order, to symbolize submission to their God.
- Religious Jews put a yarmulke on their head as a sign of humility towards God.
- Beyond its spiritual significance, the forced deprivation of hair was a mark of humiliation for the oppressed and of domination for its instigator.
- During the last world war, women who had consorted with the enemy were shaved.
Hair is perceived as an ostentatious symbol of femininity, so hair loss is a recurring concern for women.
GENERALITIES ABOUT HAIR
There are between 100,000 and 150,000 hairs on the scalp, i.e. 300 hairs per cm2.
- The diameter of a hair varies between 50 and 100 microns.
- The structure of the hair is complex.
The proteins of keratin which form the macrofibrils are linked together by disulfide bridges which are covalent bonds between the cysteine.
These bridges represent the skeleton of the hair fiber and determine its initial shape.
Straightening destroys the disulfide bridges.
THE 3 PHASES OF THE HAIR CYCLE
1.The anagen phase: this is the growth phase.
It lasts about 5 years.
C’est cette phase qui est raccourcie en cas d’alopécie androgénique. (85 %des cheveux sont en phase anagène).
The catagen phase: is the resting phase and lasts about 3 weeks and concerns 3 % of the hair.
The telogen phase: corresponds to the expulsion of the hair. it lasts 6 months and it concerns 12 % of the hair.
The number of pilar cycles would be around 25.
During the last growth cycle, the hair follicle will not be replaced by a new hair and it leaves an empty hole on the scalp.
The growth is 0.5 and 1 cm per month. The hair cycle is subject to variations in age, genetics and diet.
We have 300 hairs per square centimeter and about 150 at age 60.
This is a normal sign of aging, such as wrinkles or sagging jowls.
CYCLES VARY ACCORDING TO DIFFERENT FACTORS
- Dietary factors :
' vitamins such as vitamin B6 (pyridoxine), vitamin B5 (pantothenic acid), vitamin C and vitamin B8.
' The polyunsaturated fatty acids, linoleic and linoleic acids, reduce the harmful action of 5α reductase on the hair cycle.
- Seasonal factors: fall, spring.
Melanin synthesis by melanocytes: they color the skin, eyes and hair.
- The melanocytes present in the hair follicle are able to synthesize melanin in the absence of UV light.
- They have a protective role: melanins absorb part of the sun's rays, blocking free radicals.
A number of medications can be responsible for hair loss
- AAG chronically shortens the duration of the anagen phase of the hair cycle.
The hair cycles will be exhausted prematurely.
GAA has a high prevalence in men.
And involves about 15 % of men at age 20, 30 % at age 30, and 50 % at age 50, as well as 20 % of women at age 40.
- 5α-reductase converts testosterone to DHt.
Genes that would be carried by the X chromosomes.
They induce a sensitivity of the bulb to DHt and increase the hair cycles by decreasing the anagen phase.
- Estrogens slow down the anagen phase. During pregnancy the hair is beautiful, after childbirth the sudden drop in estrogen levels leads to hair loss.
- In hypothyroidism, hair is sparser, dry and brittle.
FROM L'ORÉAL RESEARCH AND INNOVATION. B.BERNARD & M.VERSCHOORE.
CLASSIFICATION OF HAIR ACCORDING TO ITS PHYSICAL CHARACTERISTICS
- African or frizzy: we note an elliptical section and a variable diameter on various places of the hair shaft. Like a flattened ribbon, it will tend to twist on itself and forms the hair of frizzy aspect.
- Asian: the largest diameter is noted.
Its morphology is similar to that of a cylinder. The hair is like a well-connected stem.
- Caucasian: we note a diameter and a section of intermediate size. The hair can be straight as well as curly
CLASSIFICATION BY TYPE
- Type I (steep),
- Type II (large corrugation),
- Type III (corrugated),
- Type IV (curly),
- Type V (very curly),
- Type VI (rolled up),
- Type VII (very coiled),
- Type VIII (zig zag rolled).
A strand of 100 hairs will resist a weight of 10 kilograms.
Between 0 and 2 % of extension is the "linear elongation region.
Between 2 % and 25-30% of extension is the "plastic region".
Beyond 30 % of extension is the "post-plastic region".
When the hair is wet, styling is easier.
The load is half that of a dry hair.
Frizzy hair is more fragile to traction because it is more twisted, it has flattened areas to the point of strangeness at the elbows and inversions in the direction of a twist.
The Asian hair, having a shape close to a cylinder, is very solid, independently of its diameter.
PERMEABILITY AND SWELLING
Anisotropic swelling of the fiber is observed, with an increase of 15 to 20 % in diameter and 0.5 to 2 % in length.
Frizzy hair naturally has less moisturizing substances than Caucasian hair.
CHARACTERISTICS SPECIFIC TO THE AFRICAN HAIR TYPE
The shape is helical and spiral.
The appearance appears voluminous.
Hair density is lower than that of Caucasian hair.
The lack of lipids decreases the cohesion of the cubic cells and weakens the structure of the hair.
Sebum does not flow properly because of the helical structure and the many tendrils. African hair contains 99 % of melanin.
- It has been shown by Khumalo that there are 16.5 % knots in African hair, versus a near absence of knots in other ethnic groups.
- The formation of these knots, which are very tight, affects the cuticle which frays and leaves the cortex exposed.
The sebum from the sebaceous glands acts as a lubricant for the scales of the hair shaft.
Frizzy, unruly hair is therefore less well protected.
African hair grows more slowly than Caucasian hair.
ALOPECIA INDUCED BY TRANSIENT INHIBITION OF THE HAIR CYCLE
- Due to deficiency origins such as lack of : iron, vitamin C, vitamin D, B vitamins.
- Telogen effluvium represents a sudden loss of hair after a trauma or stress between 1 and 3 months before fever, psychological stress, surgery.
- Chemotherapies are responsible for anagenic effluvium, between 1 and 3 weeks after the injections.
- Hair follicle infections can be induced by fungi (microsporum or trichophyton), ringworm, or staphylococcus aureus or propionibacteriumacnes, cause bacterial folliculitis.
- Compulsive disorders: trichotillomania.
- Diseases: peladas, lupus, lichen, scleroderma, fibrosing frontal alopecia, of some women after menopause.
ALOPECIA BY PERMANENT DESTRUCTION OF THE HAIR FOLLICLE
In this type of alopecia, the hair follicle is irreversibly destroyed and the hair loss observed is permanent.
- Agenetic lopecia: AAG. there are aplasias, hypoplasias or dysplasias of the hair follicles, congenital or acquired.
- Alendogenous surgery due to dermatoses leading to a destruction of the follicles (chronic lupus erythematosus, lichen, certain chronic folliculitis, tumors).
- Alopecia of exogenous origin Induced by traumatic factors such as burns, radiodermatitis, repeated traction, etc.
COSMETIC TRAUMATIC ALOPECIA
- The tractions are important on the hair: buns or braids, hair extensions that are too tight, too frequent brushings.
Women with frizzy hair almost systematically pull their hair. Since frizzy hair is naturally more fragile than other types of hair, these women are highly predisposed to suffer from traction alopecia. The prevalence would be : 17 % of these women from the age of 16 and 31 % from the age of 18.
- The Austrian dermatologist Trebisc in 1907 had noted definitive alopecic areas observed on the temples and at the back of the skull in young women living in the Great West Greenland region.
They used to frequently wear their hair in a ponytail as in Japan and Europe in the early 1930s. This involved populations of women elaborating hairstyles using buns.
Definitive alopecic zones are noted in African women, depending on their styling habits and the use of cosmetic products that are too aggressive for their fragile hair.
It is a non-scarring alopecia at the beginning of its evolution.
Maintaining traction on the hair shaft will lead to a definitive destruction of the hair follicle and induce a secondary permanent scarring alopecia in the frontal and temporal areas.
CHEMICAL ALOPECIA AND THE USE
- As early as 1995, an estimated 80 % of African American women had ever used a relaxer.
- It is estimated that 2/3 of African women use hair straightening to make their hair easier to style and to obtain longer hair.
- These products cause many undesirable effects including chemical alopecia.
Chemical alopecia and traction alopecia are among the top 5 most diagnosed dermatological conditions in African American women.
CHEMICAL ALOPECIA IN THE ACTIVE INFLAMMATORY STAGE
- Folliculitis will be aggravated by the use of comedogenic hair products (oils or ointments applied directly to the scalp) and by the use of allergenic synthetic hair extensions.
Pustules around the roots of hair stems exposed to high tension,
The formation of a perifollicular erythema, with a grayish appearance,
Hyperkeratosis and pruritus that suggest seborrheic dermatitis.
The alopecia is not scarring: it is still reversible.
- A particularity related to these women with African origins is a higher prevalence of martial deficiency, when a diagnosis of hair shaft fragility is made.
There are many causes, sometimes constitutional, such as sickle cell disease, or acquired, such as the ingestion of kaolin.
An iron assessment will then be useful to prescribe iron supplementation if the ferritin is below 40 μg/L .
CAUSTIC CHEMICAL ALOPECIA
- It is part of the non-scarring alopecias caused by a chemical trauma, which has the purpose of straightening.
- Frequent use of caustic cosmetics leads to irreversible scarring alopecia.
- Straightening distorts the structure of curly hair to make it smooth. The product destroys the covalent bonds of the keratin protein which are the disulfide bridges.
' Hydroxide-based relaxers: are very corrosive.
' No-lye relaxers: have less straightening power but the same corrosive effect.
' The relaxers based on thiols, or sulfites or bisulfites: are used to achieve the curly perm. This not very powerful reducer has a weak smoothing power, but it is very soft with the hair and the scalp.
' The first chemical relaxers put on the market at the beginning of the twentieth century were used exclusively by men.
Deemed very corrosive, their very rudimentary formulas contained soda, lard and boiled eggs.
It was in 1960 that African-American women began to use the chemical relaxer.
THE MECHANISM OF ACTION OF HAIR RELAXERS
- Dthiol-based relaxers : disulfide bond breaking by a reducing agent and
mechanical smoothing.- hydroxide-based relaxers : the straightening is done in one step by breaking the disulfide bonds and fixing the resulting deformation. A too long exposure time favors
the development of a chronic inflammation of the hair follicle, which will lead to scarring alopecia.
The relaxers will have effects on the scalp on the one hand and the hair shaft on the other:
Effect on the hair shaft: after a straightening, the African hair undergoes a structural deformation of its keratin protein.
Straightened and broken hair contains 3 times less cystine than non-straightened hair, when the straightener's exposure time is exceeded.
This causes the crumbling or breaking of the hair shaft and the dissolution of the hair.
The concentrations of cystine found in the distal end of the hair of relaxed individuals with or without breakage, are greatly reduced.
Formulas with a very alkaline ph between 13.2-13.3 are responsible for burning of the
CENTRAL CENTRIFUGAL SCARRING ALOPECIA
These traumas are due to chemical aggressions (straightening) and mechanical aggressions (traction).
They cause chronic inflammation of the hair follicle cells with :
- Premature degeneration of the internal epithelial sheath.
- Inflammation leading to the formation of a lymphocytic infiltrate.
- A fibrous tissue aggregates around the hair follicle.
- The inflammation becomes chronic, a granulocytic infiltrate amplifies the inflammatory reaction.
- Stem cells in the bulge area are affected by these inflammatory reactions
repeated, they generate a degeneration of the hair follicle which will not be able to produce
- Loss of the sebaceous gland.
- The only thing that remains is the hair-retaining muscle.
Alopecia begins in the center of the scalp, which presents a circular, hairless, smooth, sometimes shiny area with no apparent inflammatory zone.
The alopecia is chronic and its progression allows an expansion of the alopecic plaque in a centrifugal manner.
- The interrogation specifies the occurrence of the pathology:
' The date of the beginning of hair loss to estimate its age.
' The circumstances of the occurrence of this fall.
' The evolution over time to know if the fall is acute or chronic.
' Styling methods: patients' hair care habits.
Use of effluvium-inducing drugs.
' Presence of general disorders, chronic disease (asthenia, hyposideremia).
' Family history.
The search for localizations other than the scalp (to eliminate autoimmune diseases such as lupus erythematosus).
Examination: clinical exploration of the scalp and hair.
The examination of alopecic areas is done with a magnifying glass or a dermatoscope.
A dermatoscope or magnifying glass may be all that is needed to make a diagnosis of scarring alopecia.
We look for signs of primary scarring alopecia which are:
Irregular spaces between the hairs; this is called "tufting".
Erythema, desquamation, perifollicular hyperkeratosis.
Depigmentation and pain in the inflammatory area.
History of keloids.
The presence of dandruff and pain on the scalp.
A dry or dull appearance is suggestive of hypotrichosis or a deficiency disorder.
Short and fine hair, miniaturization of the hair bulb of bitemporal and or tonsorial topography in androgenetic alopecia.
Hair in the shape of an "exclamation point" and circumscribed alopecia are pathognomonic of alopecia.
A diffuse form in case of telogen effluvium.
Border or marginal alopecia in the case of traction alopecia.
Alopecia of the vertex in women with frizzy hair suggestive of central centrifugal scarring alopecia.
- The trichogramma.
Can help determine the etiology of some hair loss.
For diffuse hair loss.
In children, it is used to diagnose deciduous anagen hair syndrome.
To quantify the extent of the fall and monitor the effectiveness of a treatment.
- The manual pull test
On unwashed hair for 48 hours.
Performed on three distinct areas of the scalp.
Pinch a strand of hair between thumb and forefinger.
It is considered normal when the result allows to collect between 1 and 3 hairs per tested area.
- Androgenetic alopecia: the location of the alopecic areas located on the vertex.
- Traction alopecia.
In the case of centrifugal central scarring alopecia, hair follicles are distinguished on histological sections by biopsy of the alopecic area:
- Total loss of the internal epithelial sheath surrounding the cortex.
- A beginning of inflammation.
- The formation of a thin fibrous tissue surrounding the cortex.
- A perifollicular desquamation.