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Kerastase

Résistance Masque Extentioniste

Mask / Weekly treatment, lean

  • Mask / treatment
  • Sulfate-free
  • Protein-free
  • Not cruelty-free · PETA-listed
Size6.8 fl oz
Price$70seen at one store · 6.8 oz
Price / oz$10.29/ozat 6.8 oz
Where to buy1 store

Scent:

The ingredient list declares fragrance. What it smells of is not stated, and we do not guess.

Manufacturer page: inkeedecoder.com

Personal fit

Is this right for you?

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Priced above most masks and treatments

$10.29/oz at 6.8 oz — more than 92% of the 347 masks and treatments , which mostly run $1.63–5.74/oz.

Price and stores

Great for

Protein-sensitive hairthat stiffens when protein is added
Maximum slipfor hair that tangles the moment it is wet
Porous, damaged hairceramides are in the list
Cuticle-smoothing pHa pH adjuster brings it to the acidic range hair prefers
A wide range of haira middle-of-the-range weight

Maybe skip if

this product carries a scent
Curly-method routinesthese silicones need a detergent to remove
Very dry or damaged hairit contains fast-drying alcohol
Hair that needs proteinthere is none in this list
Very dry hairno humectant appears in the list
Vegan and cruelty-freeour record does not support both claims here

Whether your hair needs moisture, protein, or bond repair right now depends on your damage history and how your hair behaves wet — that is what the consultation works out.

What the formula actually does

Read from the label, not the marketing

Each row says where it comes from: F means we derived it from this product’s own ingredient list, S means it is a claim the brand makes that the formula neither confirms nor contradicts.

Oils and butters None

No oils or butters in the list.

Weight on the hair Medium

Middle of the range — noticeable on fine hair, light on coarse hair.

Protein None

No protein or amino acids in the list.

Water-binding (humectants) None found

No humectants found — nothing here pulls water into the hair.

Slip and detangling High

Conditioning agents sit high in the list — this is a detangling formula.

Needs detergent to remove Yes

Water-insoluble silicones or waxes: a detergent wash is what removes them.

Fragrance Present

Fragrance is listed; it sits below the working ingredients.

from the formula stated by the brand reported by reviewers Scale: 1 dot low · 5 dots high, within this product type.

Ingredients that matter

The ingredients that change a decision

The workhorse ingredients plus anything lower down that changes a decision. These chips name what an ingredient does — they are not safety scores, and no ingredient here is rated good or bad on its own.

IngredientWhat it doesWhy it mattersChip
WaterAqua/Water solvent The base everything else is dissolved in Neutral
Cetearyl Alcohol fatty alcohol Thickens and conditions — not a drying alcohol Softens
Amodimethicone silicone Smooths the cuticle and adds shine Buildup
Behentrimonium Methosulfate conditioning agent Conditions and softens — this is what makes it comb through Detangles
Behentrimonium Chloride conditioning agent Conditions and softens — this is what makes it comb through Detangles
Ethanolamine pH adjuster Fine-tunes the pH pH balancer
Maleic Acid pH adjuster Fine-tunes the pH pH balancer
Phenoxyethanol preservative Keeps the product from spoiling Stabilizes
Isopropyl Alcohol drying alcohol A small amount, for fast drying Drying
Amyl Cinnamal fragrance The scent Fragrance
Hexyl Cinnamal fragrance The scent Fragrance
Linalool fragrance The scent Fragrance
What the list leaves out, and what it carriesThe list carries no sulfates. No protein — a moisture formula, not a repair one. Fragrance is on the label. Water-insoluble silicones — needs a detergent wash to remove.
Full ingredient list (24)

US labelling rules put ingredients above 1% in descending order of amount; below 1% they may be listed in any order. Annotations keep three readings separate: the ingredient's general function, its role in this product type, and what its position can support.

  • 1 Water · Aqua/Water
    General function

    The base of almost every rinse-off and cream hair product. It carries everything else and is normally the first ingredient on the label.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    • solvent
  • 2 Cetearyl Alcohol
    General function

    A waxy fatty alcohol - nothing like drying alcohol. It gives conditioners their body and leaves a soft, smoothing film on the hair.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitDry, coarse, or high-porosity hair

    The waxy solid that gives a conditioner its body. It deposits a soft lubricating layer, which is most of what makes hair feel smooth after rinsing.

    May suitFrizz-prone, damaged, or high-friction hair

    Deposits with the cationic conditioners and helps them lie flat along the strand, which is where the detangling actually comes from.

    DependsFine or easily flattened hair

    Near the top of a conditioner it is doing most of the conditioning, and most of the weighting, at the same time.

    PubChem
    • fatty alcohol
    • emollient
    • thickener
  • 3 Amodimethicone
    General function

    A silicone modified to stick where hair is damaged, so it smooths selectively instead of coating everything. It resists rinsing more than plain dimethicone.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitClimate-sensitive or frizz-prone hair

    A surface film slows how quickly humidity reaches the cortex, which is what limits swelling-driven frizz in damp air.

    May suitFrizz-prone, damaged, or high-friction hair

    Amino-functional silicone carries a positive charge, so it binds where the cuticle is worn rather than coating evenly. Damaged areas get most of it.

    May suitMaximum-hold styling

    Film formers are what hold a style: they dry into a connected film across the strands so the shape resists movement.

    International Journal of Trichology
    • silicone
    • conditioning agent
    • film former
  • 4 Behentrimonium Methosulfate
    General function

    A mild cationic conditioner known for heavy detangling with a light rinse-out feel. Common in curly-hair conditioners.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    May suitDry, coarse, or high-porosity hair

    A C22 conditioning quat, the chain length that deposits most heavily in electrokinetic testing. It is the slip coarse or porous hair usually needs, delivered by chain length rather than by charge alone.

    May suitFrizz-prone, damaged, or high-friction hair

    A cationic conditioning agent: it binds to the damaged, negatively charged parts of the cuticle and lowers combing friction there.

    May suitVery dry or highly damaged hair

    The class that does the detangling in a conditioner. It deposits lubrication where the cuticle is worn.

    International Journal of Cosmetic Science
    • conditioning agent
    • emulsifier
  • 5 Behentrimonium Chloride
    General function

    A positively charged conditioning agent that binds to damaged, negatively charged spots on the hair. It is the main detangling ingredient in most rinse-out conditioners.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    May suitDry, coarse, or high-porosity hair

    Electrokinetic measurement puts the C22 quat ahead of the C16 ones for deposition: the longer chain adds van der Waals stabilisation on top of the charge binding. That extra deposit is what coarse hair usually needs to comb through.

    May suitFrizz-prone, damaged, or high-friction hair

    A cationic conditioning agent: it binds to the damaged, negatively charged parts of the cuticle and lowers combing friction there.

    DependsBuild-up-sensitive routines

    Substantive by design. A routine with no detergent wash gives it nothing to leave with.

    International Journal of Cosmetic Science
    • conditioning agent
    • cleanser
  • Below about this point, order stops being meaningful — these are typically used at 1% or less.
  • 6 Ethanolamine
    General function

    A base used in trace amounts to neutralise acidic polymers so a gel thickens.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    • pH adjuster
  • 7 Maleic Acid
    General function

    An acid used to adjust pH and, in bond-repair systems, as part of the reactive chemistry.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    DependsFrizz-prone, damaged, or high-friction hair

    pH adjusters are how a formula is brought to a chosen acidity, and an acidic formula keeps the cuticle lying flatter than an alkaline one. Which way this one moves the pH depends on the formula, and the finished pH is not on the label.

    • pH adjuster
  • 8 Phenoxyethanol
    General function

    The most common modern preservative; it keeps the product free of bacteria and mould. It sits well below 1% of the formula.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    PubChem
    • preservative
  • 9 Isopropyl Alcohol
    General function

    A fast-evaporating alcohol used as a solvent and to speed drying. Well down the list it is a processing aid; near the top it can leave hair feeling dry.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitFine or easily flattened hair

    Evaporates on contact, which is how a spray sets almost instantly and leaves no weight behind it.

    PubChem
    • drying alcohol
    • solvent
  • 10 Benzoic Acid
    • preservative
  • 11 Trideceth-6
    • emulsifier
    • solubilizer
  • 12 Hydroxypropyl Guar
    General function

    A modified guar gum used to thicken and give a slippery, cushioned feel.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitCurls or waves needing flexible hold

    Gums thicken and set soft, which gives definition that bends rather than a rigid cast.

    May suitMaximum-hold styling

    A styling polymer dries into a film across the strands, which is what makes a shape hold instead of relax.

    • gum
    • thickener
    • polymer
  • 13 Amyl Cinnamal
    General function

    A jasmine-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 14 Hexyl Cinnamal
    General function

    A jasmine-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 15 Benzyl Alcohol
    • preservative
    • solvent
  • 16 Cetrimonium Chloride
    General function

    A quick-acting conditioning agent that reduces static and combing force. It also helps keep the formula stable.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitFine or easily flattened hair

    The C16 quat binds mostly by charge rather than by chain, so it deposits measurably less than the C22 ones. Less deposit is less conditioning and also less weight, which is usually the trade fine hair wants.

    May suitFrizz-prone, damaged, or high-friction hair

    A cationic conditioning agent: it binds to the damaged, negatively charged parts of the cuticle and lowers combing friction there.

    DependsBuild-up-sensitive routines

    Substantive by design. A routine with no detergent wash gives it nothing to leave with.

    International Journal of Cosmetic Science
    • conditioning agent
    • cleanser
  • 17 Linalool
    General function

    A floral fragrance component listed separately as a recognised contact allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 18 Hydroxycitronellal
    General function

    A soft floral fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 19 Citronellol
    General function

    A rose-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 20 Limonene
    General function

    A citrus-smelling fragrance component that EU rules require to be named separately because some people react to it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 21 Benzyl Cinnamate
    General function

    A balsamic fragrance component listed as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    • fragrance
    • named fragrance allergen
  • 22 Creatine
    General function

    An amino-acid derivative used in strengthening-positioned products; it is small enough to enter the strand.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitFrizz-prone, damaged, or high-friction hair

    Deposits a lubricating layer that makes combing easier, which is most of what stops mechanical damage adding to frizz.

    May suitVery dry or highly damaged hair

    Amino acids are the smallest protein fraction and bind water as well, so they add far less stiffness than a hydrolysed protein does.

    DependsProtein-sensitive hair

    The lightest option in the protein family, but still protein — worth watching if protein reliably stiffens your hair.

    • amino acid
    • conditioning agent
  • 23 2-Oleamido-1,3-Octadecanediol
    General function

    A ceramide-like lipid used to reinforce the outer surface of damaged hair.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitFrizz-prone, damaged, or high-friction hair

    Restoring surface lipids lowers friction between strands, which is where much of the roughness in damaged hair comes from.

    May suitProtein-sensitive hair

    A lipid, not a protein, despite sitting alongside proteins in most repair claims. It does not carry the stiffening effect.

    May suitVery dry or highly damaged hair

    Ceramides are the lipid class bleaching and heat deplete. Replacing them works on the surface layer rather than adding protein stiffness.

    • ceramide
    • emollient
  • 24 Fragrance · Parfum/Fragrance
    General function

    An undisclosed blend of scent ingredients. Regulations let it stay unlisted, so a fragrance-free product is the only way to be certain what is not in it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    Declared fragrance. On a fragrance-sensitive routine this is the line that decides it, wherever it sits on the label.

    • fragrance
    • declared fragrance

What the whole list adds up to

  • 8 fragrances
  • 7 named fragrance allergens
  • 3 solvents
  • 3 conditioning agents
  • 3 preservatives
  • 2 emollients
  • 2 thickeners
  • 2 conditioning agents
  • 2 emulsifiers
  • 2 cleansers
  • 2 pH adjusters
  • 1 fatty alcohol
  • 1 silicone
  • 1 film former

Ingredient list captured 2026-09-17. Formulas change — check the package in your hand when an ingredient matters to you.

Price · 6.8 oz

Seen at $70 1 store · checked Sep 17
Show the price ladder
Where we’ve seen it1 listing · 1 store

Sorted by price per ounce. Dated observations from our research, not live prices. Direct store pages, no affiliate links. We don’t sell this product.

How we work this out
  1. 6.8 oz is the size stores list most often; every comparison on this page is made at it. Other sizes are shown in the Sizes row and the store list.
  2. Seen at $70 is the price we have observed for the 6.8 oz. We need three stores before we call a price commonly seen.
  3. About $24 is what masks and treatments typically cost at this size. Too few of the products that do the same job carry a price for us to draw a good-value line.

Formula

Formula score
5 of 10

Above the range for masks and treatments per ounce, on a formula that covers the middle of the format and has no close, cheaper equivalent in our library.

How the score is counted
  • Nothing in our library does the same job for less
  • Costs more per ounce than 92% of the 347 masks and treatments we’ve priced
  • No rich emollients in the formula
  • Prestige tier, sold at Salons
  • Rich emollientsThe depth a treatment step is built around.3 pts
  • Conditioning agents up frontWhat makes wet hair comb through.2 pts
  • Protein or amino acidsThe strengthening side of a treatment.2 pts
  • A humectantBinds water into the hair.1 pt
  • A stated dwell timeThe brand says how long to leave it on.1 pt
  • Fragrance kept out of the top eightScent as a finishing touch, not a major share.1 pt

The formula score is completeness for the job: the share of the systems this product type is normally built around that we can find in this list, weighted. It is not efficacy, not quality, and it never compares across product types.

Similar products

Suits every hair pattern

Final decision

Should you buy it?

Only if you need exactly this
Best user

Hair that stiffens on protein — for a protein-free formula and real detangling slip

Biggest tradeoff

Less suited to anyone sensitive to fragrance, curly-method routines, or very dry or high-damage hair

Best alternative if not

Nothing in our library matches it closely at a lower price.

We do not sell products or take placement fees. This page states what the formula and the prices show; the consultation is what matches it to a person.

Claims check

What the brand says, against what the formula shows

Claims are quoted from the brand. We only mark one supported, partly supported, or conflicting when the ingredient list actually speaks to it; everything else stays "stated by the brand", which is not a criticism — most claims simply cannot be read off a label.

1
SupportedBacked by ingredients
2
Partly supportedSome supporting logic
1
Stated by brandNo clear evidence
0
Potential conflictFormula works against claim
strengthens brittle and damaged hair

Protein or ceramides are present, but low enough that this reads as support, not treatment.

  • Behentrimonium Methosulfate
  • Behentrimonium Chloride
  • Cetrimonium Chloride
Partly supported

Supports the surface, not a treatment.

boosts shine

The formula carries a recognised shine system — silicone, oil, or light ester.

  • Amodimethicone
Supported

Reflects light for visible shine.

helps banish split ends

Protein or ceramides are present, but low enough that this reads as support, not treatment.

  • Behentrimonium Methosulfate
  • Behentrimonium Chloride
  • Cetrimonium Chloride
Partly supported

Supports the surface, not a treatment.

for long/damaged lengths

This is a marketing claim; an ingredient list cannot speak to it.

Stated by brand

Can’t be confirmed from label.

How to read this

We look at the first 10–15 ingredients and what they do in a formula — not marketing. If the list doesn't speak to a claim, we don't assume.

Reviewers

What people report

Recurring themes our researchers wrote in their own words from sourced reviews. We do not store or scrape star ratings.

Several reviewers say results were inconsistent for their hair type, with a few finding it too light or thin to make a real difference.

A recurring criticism is an overpowering, long-lasting fragrance that some reviewers describe as headache-inducing.

Many say it leaves hair silky, smooth and shiny without weighing it down when used sparingly, as directed.

Reviewers with long, damaged or over-processed hair consistently report reduced breakage and easier detangling within weeks of regular use.

A number of long-time users note the formula, color or scent changed from earlier purchases and did not perform as well as the version they remembered.

More from Kerastase

How this page was made

  • Everything above is generated from our researched product record — identity, the ingredient list as printed, the brand's own claims, dated price observations, and review themes written in our researchers' own words. No part of this page is written per product.
  • The value band is a fixed label over two stored numbers: this product’s cost per ounce as a percentile of every product of this type we have priced, each at the size it is most often sold in, and how many products we score as doing the same job cost at least a quarter less per ounce.
  • Both scores out of ten are defined on this page. The formula score is completeness for the job, computed from a fixed per-format checklist shown beneath the gauge; the price score is cost per ounce against every product of this type we have priced.
  • The "Is this right for you?" panel reads only your own consultation answers, and it applies exactly the filters our recommendation engine applies. It is computed when you load the page and is never stored on it.
  • 4 sources consulted for this product (1 manufacturer or regulatory, 1 retailer, 2 editorial), last checked 2026-09-17.
  • Ingredient references are linked for 12 of 18 product-aware annotations on this page. Fit notes are conditional formulation guidance, not a conclusion about the finished product or about you.
  • We have not tested this product in a lab and we do not physically test your hair. Formula readings come from the ingredient list; behaviour claims are labelled as the brand's.
  • Ingredient order tells you relative amount only above roughly 1%. Prices are observations on the dates shown and change without notice.
  • Ingredient names link to our ingredient library, where each entry shows what it does, which product types use it, and where it usually sits on a label across everything we have researched.
  • This is cosmetic information, not medical advice, and nothing here diagnoses or treats a health condition.
  • Formula readings: derivation v22. Record last updated 2026-09-17.