Hair is a complex hair element that is an integral part of our anatomy. With approximately 100,000 to 150,000 hairs on our scalp, each with its own life cycle, it is essential to understand the process of growth and renewal.
The hair life cycle
Whether you have short, long, frizzy, straight or curly hair, the life cycle of hair is on average 3 years for men and 4 to 6 years for women, influenced by factors such as:
- and psychological health.
The hair life cycle can be divided into four distinct phases:
- the anagen phase,
- the catagen phase,
- the telogen phase,
- and the fall phase.
This pattern repeats approximately 25 times during life, so we can estimate that hair is capable of growing for 100 to 125 years.
The hair growth phase, called the anagen phase , is a complex process that can last 4 to 7 years, depending on the individual and their gender.
During the anagen phase, hair develops from the hair bulb, which provides the nutrients and elements necessary for hair growth. The hair also draws its vitality from the arterioles which irrigate the scalp, thus providing important nutrients to the root of the hair bulb.
In addition, the matrix part of the hair also plays a crucial role in providing mineral, water and sebaceous elements from the sweat and sebaceous glands. These elements nourish the cells which cluster around the medullary canal, thus ensuring the health and vitality of the hair.
After the anagen phase, the hair transitions to the catagen phase , which is a transitional period of approximately two to three weeks, during which keratin production stops and dermal papilla 1 retracts.
Then, the hair enters the telogen phase , which is the resting and shedding phase of the hair. This phase lasts on average 3 months and the hair falls out naturally, to be replaced by new hair which is already in the anagen phase. Fortunately, nature is well-made, the hair that falls out is immediately replaced by another in order to preserve the overall aesthetics of the hair. Approximately 15% of hair is in the telogen phase at any one time.
It is important to understand that not all hair is in the growth phase at the same time. Indeed, there is a percentage of hair in the anagen phase, a percentage in the catagen phase and a percentage in the telogen phase at any time. This is why we naturally lose around 40 to 80 hairs per day, which is considered normal.
Finally, the shedding phase is the phase where the old hair falls out on its own to make way for the new growing hair. This phase is important because it is during this time that the germ cells located at the root of the hair bulb will produce a new hair.
However, certain factors such as stress, nutritional deficiencies, hormonal changes and diseases can disrupt the hair life cycle, leading to excessive hair loss or loss of vitality. This is why it is important to take care of our hair and our overall health to ensure the health and vitality of our hair.
As a scalp specialist, we recommend taking care of our hair and overall health to ensure the health and vitality of our hair throughout its life cycle.
And when the fall accelerates...
We will successively see the different cases of alopecia (temporary, total or partial loss of hair and/or hair).
We can distinguish 2 types of hair loss. The first called progressive and the second called reactionary.
- Progressive hair loss is characterized by a progressive and regular loss of hair density over a long period (more than 6 months), often due to a hereditary or hormonal factor.
In men, it often manifests as crown baldness or hair loss at the temples, while in women it is often localized on the crown and midline of the skull, where the hair becomes more thin, sparser and the scalp more visible.
- Reactive hair loss is linked to external events such as stress, dietary deficiencies, hormonal changes, taking medications, infection, autoimmune disease or even surgery. It often manifests in a diffuse and temporary manner and may be followed by hair regrowth once the underlying cause is treated.
It is therefore important to clearly identify the cause of hair loss in order to choose the most suitable treatment.
Indeed, the density of the scalp and the vigor of the hair can be impacted by different factors. Age is an important factor, as hair follicles tend to reduce in size and number over time. Hormonal variations can also play a role in hair loss, particularly in women, with menopause or taking certain contraceptives. Heredity is also an important factor, as baldness can be passed down from generation to generation.
Hair loss can have an impact on morale and self-confidence, which is why more and more people are seeking to take care of this problem at the first signs. Consumers are increasingly demanding about the effectiveness of formulas. They are increasingly attentive to the composition of products used to treat hair loss, demanding an eco-designed and environmentally friendly approach.
The different cases of progressive fall
As we saw in the first part, the life cycle of a hair is made up of three phases: the growth phase (anagen), the transition phase (catagen) and the resting phase (telogen). The life cycle of a hair repeats itself 25 times during its life.
During the growth phase, hair actively grows for several years. Then, the transition phase marks the end of growth and the hair follicle begins to shrink. Finally, during the resting phase, the hair is no longer nourished and falls naturally to make way for new hair in the growth phase.
In the case of androgenic alopecia, the hair growth phase is gradually shortened under the influence of hormonal factors, in particular androgenic hormones. This reduction in the growth phase causes a gradual decrease in hair density, until the hair becomes sparse and fine.
- The causes of androgenetic alopecia
Androgenetic alopecia results from two factors: a genetic predisposition and the action of androgens , the male sex hormones (but nevertheless present in small quantities in women). This hormonal cause also explains why this phenomenon of thinning hair only begins after puberty.
Genes predisposing to androgenetic alopecia have been identified, one of which is carried on the X chromosome (transmitted to men from their mothers). Thus, among men, the probability of suffering from baldness is higher when it is present in the maternal family.
Androgenetic alopecia is linked to the non-neutralization of male hormones by the body and to the genetic predisposition of hair follicles to be sensitive to the action of these hormones. In the presence of a favorable genetic background, the hair follicles on the top of the head are particularly sensitive to the action of androgens, and in particular a substance derived from testosterone (DHT, dihydrotestosterone ). Under the action of this hormone, the hair growth cycle is accelerated and shortened . The hair becomes finer, less dark and falls out more quickly . The 20 to 25 growth cycles that are supposed to last a lifetime are exhausted in a few years. The hair follicles located on the sides of the skull are less sensitive to the action of the hormone and their growth cycle is less disrupted.
In women , other hormonal factors can promote androgenetic alopecia: oral contraceptives (“pill”) or hormonal treatments for menopause. In addition, stress and excess blood cholesterol could also be risk factors for alopecia in women.
In summary, the hair growth cycle shortens, the cycles therefore follow each other more quickly, giving way to finer hair. The follicle becomes thinner and exhausted before dying and disappearing. The 25 hair cycles that were supposed to last a lifetime end much earlier than expected, possibly giving way to partial or total baldness.
Furthermore, DHT will also harm the healthy environment of the hair. This leads to an acceleration of the hair cycle, as well as hyperseborrhea which causes thickening of the scalp and prevents the blood vessels from properly irrigating the roots.
These two phenomena combined will cause weakened hair to fall out before reaching its maximum length. They then give way to new regrowth which will also have a shortened lifespan. The hair grows back finer, less dense, and shorter.
If we cannot cure alopecia, we can, however, slow down its progression.
In order to treat early androgenetic alopecia, it is essential to intervene as quickly as possible before the hair's life cycles are irreversibly exhausted. The objective is to extend the lifespan of the hair by preserving and extending the anagen growth phase, while avoiding the acceleration of hair life cycles.
In order to respect the sensitivity of your scalp, and your health in general, it is important to favor treatments based on natural active ingredients such as essential oils and plant extracts. Effective natural products that help preserve our health and our environment.
Indeed, hormonal alopecia is not linked to a genetic origin unlike androgenetic alopecia. It is caused by hormonal variations which can cause excessive hair loss in women. Female hormones such as estrogens, progesterone and androgens are involved in this type of alopecia.
In pregnant or postpartum women, hormonal alopecia is often due to a sudden drop in hormones after childbirth. This hormonal drop can also occur during menopause. In these cases, hair regrowth generally occurs spontaneously after the body has regained its hormonal balance.
However, there are other causes of hormonal alopecia that require medical attention. For example, taking the wrong contraceptive pill can cause hair loss in women. In this case, it is important to consult a doctor to adapt contraception. Hormonal treatments such as hormone replacement therapy can also cause hair loss in some women.
It is therefore important to clearly identify the cause of hormonal alopecia to implement the appropriate treatment and promote hair regrowth.
Alopecia during which the hair root is destroyed and replaced by a fibrous scar. The scalp is smooth and regrowth is not possible.
Scarring alopecia is a form of alopecia in which hair loss is irreversible due to the destruction of hair follicles and their replacement with scar tissue. It can be caused by inflammatory and dysimmune diseases, infections or trauma. The most common forms are lichen planus pilaris, cellulitis dissecans, Quinquaud's folliculitis decalvans and erosive pustulosis of the scalp.
The different cases of reaction drop
According to the medical dictionary of the Academy of Medicine, telogen effluvium is defined by hair loss in the telogen phase (involution period), diffuse and homogeneous, excessive, pathological, acute or chronic.
Under the effect of a triggering cause, a high number of hair follicles enter prematurely and synchronously into the catagen phase then into the telogen phase; excessive hair loss is observed two to three months later, leading to diffuse but reversible alopecia after cessation of effluvium. The causes of acute telogen effluvium are varied: psychological or emotional shock, surgical intervention, high and prolonged fever, acute or chronic anemia, childbirth, taking certain medications, etc.
There are generally three forms of telogen effluvium: sudden, late and chronic. The first form is acute hair loss, that is to say sudden and temporary, which can be due to a stressful situation or to drug treatment such as chemotherapy, for example. The second form appears several months after suffering an emotional shock and also remains reversible. The last form reflects regular and persistent hair loss which can lead to androgenetic alopecia if you have a favorable genetic background.
Telogen effluvium is therefore, most of the time, a temporary problem which ends with hair regrowth within a few months.
Alopecia areata, also known as alopecia areata, is an autoimmune condition that is characterized by localized or generalized hair loss . This disease can affect people of all ages and genders.
Alopecia areata is caused by an autoimmune reaction where the immune system attacks the hair follicles, causing inflammation which can lead to hair loss.
Symptoms of alopecia areata can vary from person to person, but they are generally characterized by patchy hair loss without itching or pain. Hair may grow back spontaneously after a few weeks or months, but it may take longer for some people, and in others the hair may not grow back.
Translational alopecia results in progressive hair loss in the frontal area, temples or, in the most severe cases, over the entire scalp. Inflammation, slight irritation or even a little hair loss are warning signs.
Traction alopecia is caused by styling practices that are traumatic for the hair roots (buns, very tight ponytails, braids, braids that are too heavy, weaving, extensions, straightening). If these practices are not abandoned quickly, the hair follicles are irreparably destroyed and the hairline recedes – up to more than five centimeters.
Trichotillomania in adults
Trichotillomania is a form of alopecia that is defined as compulsively and repeatedly pulling out one's hair . This activity is quite automatic (i.e., without full awareness); others are more aware of the activity. Hair pulling is not triggered by obsessions or concerns about appearance (as in body dysmorphic disorder), but may be preceded by a feeling of tension or anxiety that is relieved by hair pulling, which is often followed by a feeling of satisfaction.
This not only contributes to weakening the hair roots, but also to accelerate the hair growth cycle until early depletion of hair capital in the affected areas.
1.Dermal papilla: Conical extensions of the papillary layer of the dermis which penetrate into the epidermis. (dictionary.academie-medicine). Dermal papillae are small protrusions in the dermis, which extend into the epidermis, carrying oxygen and nutrients to the inner layers of epidermal cells. In addition, the papillae nourish the hair follicles (the French encyclopedia).