Hair loss: understanding before treating.

6 min. read

10/07/2026

Perte de cheveux : comprendre avant de traiter.

Cellular Beauty · Journal

Hair Loss: Understanding Before Acting

Losing hair is often seen as an inevitability. This is rarely the case. In the vast majority of situations, hair loss has an identifiable cause, and a cause that can be acted upon.

The hair cycle: each hair has its own clock

Hair does not grow indefinitely. It goes through a life cycle in three distinct phases, controlled by precise hormonal, nutritional, and cellular signals. Understanding this cycle means understanding the cause of hair loss, and why some approaches take several months to show results.

The anagen phase is the active growth phase: the hair follicle produces the hair fiber at a rate of approximately 1 cm per month. It lasts from 2 to 7 years depending on genetics and nutritional status. At any given time, it concerns 85% of our hair. This is the phase we seek to prolong and strengthen.

The catagen phase is a short transitional phase (2 to 3 weeks) during which the follicle retracts and ceases production. It concerns about 1 to 2% of hair at any given time.

Hair Loss: the hair cycle (anagen, catagen, telogen) and factors disrupting hair growth, BIOLOGYST Journal — Fig. 1: The hair cycle and the main disruptive factors

The telogen phase is the resting phase: the follicle is inactive for 3 to 4 months, then the hair naturally falls out to make way for a new anagen cycle. This normally concerns 13 to 15% of hair. Losing 50 to 100 hairs per day is therefore perfectly physiological: it is the normal consequence of this rotation.

Abnormal hair loss occurs when too many follicles simultaneously switch to the telogen phase, or when the anagen phase gradually shortens. In both cases, the cause is almost always identifiable.

Key figures of the hair cycle

50–100

Hairs lost per day = strictly normal

2–3 months

Delay between triggering shock and visible hair loss

40 µg/L

Critical ferritin threshold for the follicle

90 %

Of the hair fiber is made of keratin

Clinical study

Serum ferritin and hair loss in women: a controlled study

Rushton D.H. · Clinical and Experimental Dermatology · 2002 · Vol. 27(5) · pp. 396–404

This benchmark clinical study established a direct link between serum ferritin levels and hair loss in women. The results show that a ferritin level below 40 µg/L, although considered "within normal limits" by some laboratories, is sufficient to significantly weaken the hair follicle and reduce the duration of the anagen phase.

What this means in practice: iron deficiency is now recognized as the leading cause of hair loss in women of childbearing age. A ferritin test is the first examination to request.

Access the publication →

“Hair loss is almost never inevitable. It is most often a signal: nutritional, hormonal or emotional, that the body sends.”

The real causes: five mechanisms that trigger abnormal hair loss

The vast majority of hair loss is reactive or diffuse: meaning it has an identifiable cause and is potentially reversible once that cause is corrected. Here are the five most frequent mechanisms.

The most common causes of hair loss

Telogen effluvium

The most common cause of massive hair loss. A triggering event (intense stress, fever, childbirth, surgery, severe dieting, stopping contraception) simultaneously precipitates up to 30% of hairs into the telogen phase. Hair loss occurs 2 to 3 months later, a delay that often makes it difficult to establish the link. Effluvium is reversible once the cause is corrected.

Iron deficiency (low ferritin)

Ferritin is the marker for iron storage. Below 40 µg/L, the hair follicle is weakened even if hemoglobin is normal. Iron deficiency affects between 30 and 50% of women of childbearing age and should always be investigated in cases of hair loss. Heavy periods and repeated pregnancies are the primary causes of depletion.

Nutritional deficiencies

Keratin, which makes up 90% of the hair fiber, requires sulfur amino acids (cysteine, methionine), zinc, selenium, B vitamins (biotin, B12, B9) and silicon to be synthesized correctly. Any deficiency in these cofactors slows down keratinization, weakens the hair, and shortens the anagen phase. Restrictive diets and digestive disorders are often to blame.

Hormonal imbalances

Dihydrotestosterone (DHT) is involved in androgenetic alopecia by progressively miniaturizing follicles. But other hormones also play a role: drops in estrogen (menopause, postpartum, stopping the pill), hypothyroidism, polycystic ovary syndrome (PCOS) and chronic stress via cortisol all disrupt the hair cycle.

Follicular oxidative stress

Free radicals accumulate in the scalp with age, pollution, and an oxidizing lifestyle. They damage follicular matrix cells, shorten the anagen phase, and accelerate fiber miniaturization. This is one of the mechanisms described in premature hair aging. Vitamin E and selenium contribute to the protection of cells from oxidative stress; other compounds, such as glutathione, are being studied in this area.

What the hair follicle needs to function

The hair follicle is one of the fastest regenerating cellular structures in the body. It consumes a considerable amount of energy and nutrients to maintain its anagen phase. In case of restriction, whether dietary, digestive, or related to a targeted deficiency, the follicle is one of the first organs sacrificed by the body in favor of vital functions.

Essential nutrients for hair health

Hydrolyzed keratin (Cynatine® HNS)

Keratin is the structural protein of hair. Hydrolyzed keratin provides the amino acids and peptides that make up the hair fiber. Cynatine® HNS is a patented keratin whose specific hydrolysis is described by its designers as promoting its bioavailability. Keratin is not subject to an authorized health claim: the elements below describe a mechanism and published works, not a guaranteed effect.

L-cysteine and L-methionine

These two sulfur amino acids are direct precursors of keratin. Cysteine forms the disulfide bonds that give hair its strength and elasticity. Methionine is involved in cellular protein synthesis and methylation (epigenetic regulation of the hair cycle).

Zinc

Zinc contributes to the maintenance of normal hair and nails. It is a cofactor for over 200 enzymes involved in cell division, protein synthesis, and keratinization. It is often deficient in people with restrictive diets or intestinal malabsorption.

Iron (ferritin)

Iron helps reduce fatigue and contributes to normal cognitive function. It is also involved in cell division. A ferritin level below 40 µg/L is associated, in available studies, with a reduction in the duration of the anagen phase. Lactoferrin (Lactoferrine Active+, N° 09) is a milk protein studied for its role in iron transport; it is not subject to an authorized health claim. Adjusting iron intake should be discussed with a healthcare professional, based on a dosage.

Selenium and vitamin E

Selenium contributes to the maintenance of normal hair and, with vitamin E, to the protection of cells from oxidative stress. It also contributes to normal thyroid function. Separately: a confirmed thyroid disorder requires medical diagnosis and treatment, which no food supplement can replace.

Silicon (bamboo extract)

Silicon is a trace element of the extracellular matrix. Available studies describe its role in the mechanical resistance of the hair fiber and in hair elasticity; it is not subject to an authorized health claim. Bamboo extract is one of the most concentrated natural sources of silicon.

“Hair loss is almost never an inevitability. It is most often a signal: nutritional, hormonal or emotional, that the body sends.”

Hair Nail Regenesis: an integrated approach to keratinization

Hair Nail Regenesis (No. 05) was formulated around two families of ingredients: structural substrates (keratin, sulfur amino acids, silicon) and enzymatic cofactors (zinc, selenium, iron, B vitamins), several of which benefit from authorized health claims, as listed below.

Key active ingredients · Mechanisms of action

Active ingredient	Role
Cynatine® HNS · 500 mg	Patented keratin hydrolysate. Provides amino acids and peptides that make up the hair fiber. Clinical trials conducted on this ingredient report, in participants over 90 days, reduced hair loss, improved tensile strength, and increased shine. These studies describe observational findings; keratin is not the subject of an authorized health claim, and individual results vary.
L-cysteine · 200 mg	Main sulfur amino acid in keratin. Forms disulfide bonds that give hair its cohesion and mechanical strength. Precursor to glutathione synthesis, a compound studied for its role in cellular antioxidant defenses.
Bamboo extract · 150 mg (of which silicon 112 mg)	Concentrated source of silicon. Described as involved in the perifollicular extracellular matrix; available research focuses on fiber resistance, nail strength, and hair elasticity. No authorized health claim to date.
L-methionine · 50 mg	Essential sulfur amino acid, precursor to cysteine. Involved in protein synthesis and cellular methylation, which regulates the expression of genes involved in the hair cycle.
Zinc 10 mg · Selenium 50 µg · Iron 7 mg	Fundamental mineral triad: zinc and selenium contribute to the maintenance of normal hair, selenium contributes to the protection of cells from oxidative stress, iron contributes to the reduction of fatigue and supports cellular proliferation in the matrix. A balanced combination to cover the three deficiencies most frequently implicated in hair loss.
B + A + E vitamin complex	Biotin (B7) contributes to the maintenance of normal hair and acts as a cofactor in keratin synthesis. B12 and B9 contribute to normal cell division and the reduction of fatigue. Vitamin A contributes to the maintenance of normal skin and regulates keratinocyte differentiation. Vitamin E contributes to the protection of cells from oxidative stress.

Dosage and course duration

3 capsules per day, preferably in the morning or spread throughout the day with meals. A course of treatment should last at least 2 to 3 months: a timeline dictated by the hair cycle itself. A hair entering the anagen phase grows about 1 cm per month and is only visible after 6 to 12 weeks of growth, regardless of the approach taken. Patience is key.

Discover Hair Nail Regenesis

Precautions. Vegetable-based capsule. Contains vitamin A: not recommended for pregnant women. Contains iron: if ferritin levels are low or if you experience heavy periods, consult a healthcare professional before combining multiple iron sources.

Depending on the individual: other formulas in the catalog

Depending on the context: confirmed iron deficiency, postpartum effluvium, chronic stress, other BIOLOGYST formulas target different mechanisms. The choice is ideally made with a healthcare professional, based on an assessment.

Complementary associations based on profile

Low ferritin (< 40 µg/L)

Lactoferrin Active+ provides lactoferrin, a milk protein studied for its role in iron transport and absorption; it is not the subject of an authorized health claim. Note: Hair Nail Regenesis already provides 7 mg of iron, which is 50% of the NRV. Any combination of iron sources should be decided with a healthcare professional, based on a dosage.

Post-stress or postpartum effluvium

Combine Magnesium Active+ and Serenity Flow to support nervous balance: magnesium contributes to reducing fatigue and normal nervous system function. Unmanaged stress maintains effluvium even when deficiencies are corrected.

Hair loss linked to excessive oxidative stress

Antioxidant Defense combines vitamin C, which contributes to protecting cells from oxidative stress, with quercetin and Setria® glutathione, two compounds studied in this area, with no authorized health claim to date. A profile to consider in cases of smoking, urban pollution, or intense physical activity.

Vitamin D deficiency (dosage < 30 ng/mL)

D3 Active+ (No. 11) provides vitamin D, which contributes to the maintenance of normal bones and muscle function and the normal functioning of the immune system. On the hair side, available research describes VDR receptors in the follicle and observes an association between vitamin D deficiency and increased hair loss: a mechanism under study, not an established effect. A dosage and medical advice remain the starting point.

"Healthy hair is built over several months. Supporting hair loss means supporting the follicle, not forcing it."

Frequently Asked Questions

How many hairs do we normally lose per day?

Losing 50 to 100 hairs per day is strictly physiological. At any given time, 13 to 15% of hairs are in the telogen (resting) phase and naturally fall out to make way for a new growth cycle.

Why does hair loss occur 2 to 3 months after a shock?

Because a trigger event (intense stress, fever, childbirth, surgery, severe diet) causes up to 30% of hairs to simultaneously enter the telogen phase. This phase lasts 3 to 4 months, so hair loss only becomes visible 2 to 3 months later, which makes the connection difficult to establish.

What ferritin level is associated with hair loss?

Below 40 µg/L, the hair follicle is weakened even when hemoglobin is normal (Rushton, 2002). Iron deficiency affects 30 to 50% of women of childbearing age: a ferritin level test is the first examination to request for diffuse hair loss.

How long does it take to see results?

Allow at least 2 to 3 months, regardless of the approach chosen. Hair in the anagen phase grows approximately 1 cm per month and only becomes visible after 6 to 12 weeks of growth: this duration is dictated by the hair cycle itself. In case of persistent hair loss, consulting a healthcare professional remains the first step.

What nutrients are involved in keratin synthesis?

Keratin makes up 90% of the hair fiber. Its synthesis involves sulfur amino acids (cysteine, methionine), zinc, selenium, silicon, and B vitamins (biotin, B9, B12). Further analyses of active ingredients are available in the active ingredients blog and in the BIOLOGYST Journal.

BIOLOGYST. Food supplement not a substitute for a varied and balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose. Keep out of reach of young children. This article is for informational purposes only and does not replace medical advice: in case of persistent hair loss, consult a healthcare professional.