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Kérastase Genesis Serum Fortifiant is a leave-in scalp serum intended for weakened hair and breakage-related hair fall. Kérastase’s directions are to apply up to four pipette doses section by section to a dry or towel-dried scalp, once daily, and not rinse. It is a cosmetic hair-care product, not a medical hair-loss treatment: Kérastase USA explicitly says, “Genesis is not a hair loss product.”
What is Kérastase Genesis Serum Fortifiant?
Genesis Serum Fortifiant is the scalp serum in Kérastase’s Genesis range. The international product page calls it “Genesis Sérum Anti-Chute Fortifiant”; the US page lists 90 ml and 30 ml sizes. It is distinct from Genesis Homme Sérum Anti-Chute Fortifiant, which belongs to the separate Homme line.
Kérastase positions the Genesis range for weakened hair and hair fall related to breakage. The serum is applied to the scalp, unlike conditioners and masks designed primarily for the lengths. That distinction matters if your concern is snapping or breakage along the hair shaft rather than hair coming out for another reason.
How do you use the serum?
- Apply once daily during a six-week period, following the current directions on the package for your market.
- Part the hair into sections and apply up to four pipette doses directly to the scalp. Kérastase’s international directions specify four doses section by section.
- Use on dry or towel-dried hair. The US directions also mention use between washes.
- Do not rinse; style as usual after application.
The brand’s directions differ slightly in wording across its international and US pages. If your package gives different instructions, follow the directions for the product sold in your region.
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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.
Does Genesis Serum help with hair fall?
Kérastase describes the serum as helping reduce hair fall associated with weakened hair and breakage. Its international product page reports a clinical test involving 99 people who applied the product daily for six weeks. That is a brand-reported test statement; the page information available here does not establish the study’s controls, independence, or how broadly its result applies.
The US page reports “97% less hair fall due to breakage from brushing,” but that figure is for a three-product system: Bain Hydra-Fortifiant shampoo, Fondant Renforçateur conditioner, and Sérum Fortifiant, compared with a non-conditioning shampoo. It is not a result for the serum on its own.
Rank #2
- 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.
These claims concern cosmetic care and breakage-related hair fall. They do not establish that the serum regrows hair or treats hair loss caused by a medical condition. If you are experiencing persistent, sudden, or unexplained shedding, seek advice from a qualified healthcare professional rather than relying on a cosmetic serum.
What is in the formula?
The international product page lists ingredients including water, alcohol denat., diaminopyrimidine oxide (Aminexil), piroctone olamine, caffeine, arginine, niacinamide, and ginger root extract. The US page describes the serum as silicone-free. These are product-page descriptions, not evidence that any listed ingredient independently regrows hair. Formulas and ingredient lists can vary by market, so check the packaging for the bottle you buy.
Rank #3
- CONCENTRATED HAIR TREATMENT: A lightweight leave-in serum designed to promote thicker, fuller, and denser-looking hair by supporting the scalp.
- PEPTIDE TECHNOLOGIES: Formulated with REDENSYL, Procapil, CAPIXYL, BAICAPIL, AnaGain, and High-Solubility Caffeine to visibly enhance hair vitality and promote a denser appearance.
- PLANT-BASED EXTRACTS: Contains natural ingredients such as Larix Europaea Wood Extract, Pisum Sativum Extract, and Camellia Sinensis Leaf Extract to nourish the scalp.
- DAILY USE: Apply a few drops to clean, dry scalp once daily, preferably at bedtime, for optimal results.
- FREE FROM: Cruelty-free, gluten-free, vegan, alcohol-free, and silicone-free.
How does it compare with other Genesis products?
| Product or option | Intended use described by Kérastase | What to consider |
|---|---|---|
| Serum Fortifiant | Daily scalp serum for weakened hair and breakage-related hair fall | Choose this format if you want a leave-in scalp step. |
| Bain Hydra-Fortifiant shampoo | For normal weakened hair and thin-to-medium hair | A wash product for hair and scalp; it is not a substitute for a leave-in serum. |
| Bain Nutri-Fortifiant shampoo | For dry weakened hair and medium-to-thick hair | Kérastase positions it for a different hair texture and dryness profile than Hydra-Fortifiant. |
| Fondant Renforçateur conditioner | Conditioner in the Genesis range | A lengths-care step, rather than the range’s daily scalp serum. |
| Genesis mask and heat protectant | Additional hair-lengths care and heat protection options in the range | They add routine steps; the brand’s recommendations do not mean every user needs the complete range. |
For a simpler routine, compare the concern you are addressing, where the product is meant to be applied, your hair’s dryness and thickness, and how many steps you are willing to maintain. Kérastase’s recommendation to use the full Genesis range is a brand recommendation, not proof that every product is necessary.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is it worth the cost?
The official US page lists two sizes, 90 ml and 30 ml, but no price is established here. Check the current price and package directions where you shop; prices, stock, and marketplace listings can change. To assess the ongoing cost, compare the bottle price with the amount you would use each day over the brand’s six-week application period, and decide whether that scalp step fits your budget and routine. Do not treat the range’s system-level 97% figure as evidence that buying the serum alone will produce the same result.
Quick Recap
Rank #4
- 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
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.
