Kérastase Genesis Sérum Anti-Chute Fortifiant—sold in the UK as Genesis Anti Hair-Fall Fortifying Serum—is a leave-in scalp serum marketed for weakened hair prone to falling. Kérastase’s directions call for daily use over six weeks, but its published claims do not establish that the serum regrows hair or treats medical hair loss. The photos and four-week results discussed here are from Who What Wear UK deputy beauty editor Grace Lindsay’s personal review, not our own test.
What is Kérastase Genesis strengthening serum?
It is a leave-in scalp product intended for weakened hair that is prone to falling. The product is listed as Genesis Sérum Anti-Chute Fortifiant in the US and France, and Genesis Anti Hair-Fall Fortifying Serum in the UK. Official pages list a 90 ml bottle; the UK page also lists a 30 ml size.
The naming can blur two different concerns: breakage and hair loss. The brand’s quantified breakage claim concerns reduced hair fall due to breakage in a combined product routine. Neither that claim nor the listed product directions establish treatment for follicular or medical causes of hair loss. If you are experiencing persistent, sudden, patchy, or otherwise concerning hair loss, a qualified healthcare professional can assess the cause.
What do the review photos and four-week results show?
Who What Wear UK deputy beauty editor Grace Lindsay published a first-person review with before-and-after photographs after using the serum for four weeks. She reported less shedding and roots that looked fuller, while noting that she had not seen major hair regrowth at that point. Those observations belong to one person’s experience; they are not controlled evidence, and the photographs should not be treated as proof of a typical result.
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- Fortifiant Hair Serum: A daily strengthening serum designed to prevent hair fall due to breakage from brushing. Enriched with ginger and caffeine treatment improves resistance in weak brittle hair
- Benefit: After use, 97% experience less hair fall due to breakage from brushing. Serum fortifies & strengthens to create nourished & healthy hair. Lightweight formula that will not leave residue
- Additional Benefits: Contains Arginine, an ingredient that helps stimulate healthy hair by supporting strong blood flow to the root of hair cells. Can be targeted to areas with less density
- Suggested Use: Use morning or evening for a minimum of 6 weeks. Apply 4 doses on dry or towel-dried scalp section by section. Massage to promote distribution and absorption into hair. Do not rinse.
- Genesis Collection: Use with Bain Nutri-Fortifiant Shampoo, Fondant Renforcateur Conditioner, and Defense Thermique Primer for nourished healthy-looking hair with reduced breakage. Ideal for normal to dry weakened hair.
Lindsay also wrote that she used one to two pipettes per evening. That was her personal routine, not the brand’s stated dose. Kérastase’s directions vary slightly by market, so follow the instructions for the bottle you buy.
What does Kérastase’s evidence support?
Kérastase’s US product page describes a clinical study involving 99 people using the product daily for six weeks and associates that study with a claim to “re-anchor fiber to the root.” This is a brand-reported study and claim; the product page does not establish hair regrowth or treatment of a medical hair-loss condition.
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- Fortifiant Hair Serum: A daily strengthening serum designed to prevent hair fall due to breakage from brushing. Enriched with ginger and caffeine treatment improves resistance in weak brittle hair
- Benefit: After use, 97% experience less hair fall due to breakage from brushing. Serum fortifies & strengthens to create nourished & healthy hair. Lightweight formula that will not leave residue
- Additional Benefits: Contains Arginine, an ingredient that helps stimulate healthy hair by supporting strong blood flow to the root of hair cells. Can be targeted to areas with less density
- Suggested Use: Use morning or evening for a minimum of 6 weeks. Apply 4 doses on dry or towel-dried scalp section by section. Massage to promote distribution and absorption into hair. Do not rinse.
- Genesis Collection: Use with Bain Nutri-Fortifiant Shampoo, Fondant Renforcateur Conditioner, and Defense Thermique Primer for nourished healthy-looking hair with reduced breakage. Ideal for normal to dry weakened hair.
The separate “84% less hair fall due to breakage” figure comes from an instrumental test after one application of Bain Nutri-Fortifiant shampoo, Masque Reconstituant, and serum together. It is a result for a combined routine and breakage, not a serum-only test or a measure of new hair growth.
Kérastase France also describes the serum as number one by sales volume among anti-hair-fall hair products in France from July 2024 through June 2025, citing Circana SCS BeautyTrends. The stated scope is selective perfumeries and department stores, including e-commerce; a sales ranking is not evidence of efficacy.
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- A luxurious overnight nourishing leave-in serum formulated with niacinamide that nourishes, hydrates, detangles, and enhances shine in 8 hours.
- Benefits: Boosts shine, strength, and hydration. Moisturizes from deep within the hair fiber leaving hair smooth and shinyBoosts shine, strength, and hydration. Moisturizes from deep within the hair fiber leaving hair smooth and shiny
- Additional Benefits: Overnight, in just 8 hours, this serum protects from pillow friction to strengthen hair and leaves hair with a radiant shine and smooth satin touch.
- Suggested Usage: Apply 2-4 pumps, depending on hair thickness. Distribute evenly on dry or damp hair, massage gently
How do you use the serum?
The official directions call for application once daily to a dry or towel-dried scalp, in sections, without rinsing, during a six-week period. Use the dose specified for your market:
- US directions: Apply four pipette doses.
- UK directions: Apply three to four doses.
Apply to the scalp rather than treating the serum as a rinse-out shampoo or mask. If it gets into your eyes, rinse thoroughly. Check the current package or local product page because the dose wording differs by market.
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- Night Serum: Nourishing leave-in serum hydrates, adds deep nutrition, moisturizes, and detangles to leave hair soft and shiny by morning. Protects from pillow friction, reduces frizz and hydrates hair in just eight hours as you sleep.
- Benefits: Formulated with Plant-Based Proteins to nourish hair with essential nutrients while retaining moisture and Niacinamide to lock in hydration for long-lasting hair strength.
- Additional Benefits: Intensely nourishes and detangles hair, protecting from pillow friction. Strengthens, hydrates, and enhances shine. Absorbs overnight without transferring onto pillow
- Suggested Use: Before sleep, apply one to two pumps, then massage into lengths and ends of dry or damp hair. Leave in overnight. No need to rinse in the morning. Repeat three nights a week.
- Nutritive Collection: Ideal for all hair types prone to dryness. For best results use conditioner and/or mask, and heat protectant during the day and 8H magic night serum as a part of your nighttime routine.
Do ingredients differ by market?
Yes. The official US ingredient list includes caffeine, arginine, niacinamide, ginger root extract, diaminopyrimidine oxide (Aminexil), and piroctone olamine, among other ingredients. The French listing includes creatine and does not list caffeine. Ingredient lists can change, so use the list on the bottle sold in your market when checking for a particular ingredient or sensitivity.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which size and market should you compare?
At the time the official pages were accessed, the listed sizes and prices were as follows. Prices can change and currencies should not be compared without accounting for exchange rates.
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- Defense Thermique Blow Dry Primer: A fortifying heat protectant spray for hair that is prone to falling due to breakage from brushing. Helps prevent split ends and leaves hair shiny & silky
- Benefits: Strengthens and protects for heat styling. Enriched with ginger root and edelweiss native cells for 24H protection against frizz even in high conditioners of humidity.
- Additional Benefits: After use, 99% less hair fall due to breakage from brushing and 88% experience smoother and conditioned hair. Leaves hair easy to detangle and calms down frizz
- Suggested Use: Apply a small amount of treatment to lengths. Style as normal. Do not rinse. Can also be used on dry hair, to tame frizz and smooth ends. In case of contact with eyes, rinse immediately
- Genesis Collection: Use along with Genesis Bain Hydra-Fortifiant Shampoo & Fondant Renforcateur Conditioner for hair that is healthy-looking through boosted nourishment & protection and less hair fall due to breakage
| Market | Listed size and price | Approximate price per ml | Source |
|---|---|---|---|
| UK | 30 ml: £23.50 | About £0.78/ml | Kérastase UK |
| UK | 90 ml: £52.00 | About £0.58/ml | Kérastase UK |
| France | 90 ml: €56.90 | About €0.63/ml | Kérastase France |
The UK 90 ml listing costs less per milliliter than its 30 ml listing based on those displayed prices. Before buying, confirm that the seller is authorized, the bottle’s formula and size match your needs, and the return policy works for you. A smaller bottle lowers the initial spend but provides less product; the pages do not establish how long either size will last for an individual user.
Is Kérastase Genesis serum worth considering?
It may suit someone looking for a leave-in scalp product to use as directed for weakened, breakage-prone hair, provided they understand the limits of the evidence and the price for their market. The brand-reported six-week claim and combined-routine breakage result should not be mistaken for proof of regrowth. Lindsay’s four-week photos offer a personal reference point, not a forecast of what another user will see.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
