Free Standard Shipping within the US on $50+ Orders
free returns. buy with confidence
Leave-In Molecular Repair Hair Mask 5mL
4.7
Rated 4.7 out of 5 stars
8,129 Reviews

leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage
OR

Every purchase supports K18 x Plastic Bank efforts to radically simplify waste.

In 2022 we stopped 147 Metric tons of plastic
=
7.3M+ single-use plastic bottles from reaching the ocean

Description

A leave-in treatment mask for all hair types that clinically reverses damage in 4 minutes. The patented peptide technology works to repair damage from bleach, color, chemical services & heat – restoring strength, softness, smoothness, and bounce to hair.

Repairs Damage Caused By

  • Bleach + Color
  • Heat
  • Chemical Services

IN the shower

  1. Shampoo, do not condition.

OUT of the shower

  1. Towel dry thoroughly.
  2. Begin with 1 pump of the K18 Mask and add more as needed depending on the length, thickness, and condition.
  3. Work evenly into hair from ends to roots, one pump at a time.
  4. Let sit for 4 minutes to activate.
  5. Do NOT rinse out.
  6. Style as usual.

creates hair like new

Traveling deeper into the inner layers of hair than traditional repair products, our revolutionary patented K18Peptide™ is just the right size and makeup to fit in and reconnect broken keratin chains, renewing hair with strength, softness, smoothness, and bounce. You can feel and see the difference with the first use.

Start by using K18 after the first 4-6 washes. Then switch to maintenance mode for a boost of renewed strength, softness, smoothness, and bounce when needed.

  • DO use a clarifying shampoo if you’re a heavy product or dry shampoo user to remove buildup and help our peptide penetrate and get where it needs to go.
  • DO wait the full 4 minutes before styling or applying other product
  • DO use every 4-6 shampoos consecutively to see and feel ongoing results
  • DON’T condition your hair before application (trust us, most won’t need it after K18, if you still need, add a leave-in after the 4-minute window is up post-application)
  • DON’T overuse, a little goes a long way.
  • DON’T rinse out. This is a leave-in, so you know, leave it in!

Our K18Peptide™ is clinically proven to reverse damage in just 4 minutes.

  • Heals damage from bleach, color, chemical services, and heat
  • Restores strength, softness, smoothness, and bounce
  • Doesn’t wash away with shampoo, leaving lasting results
  • Vegan, color-safe, cruelty-free

up to 91% original strength*
up to 94% original elasticity*

* Results observed in a clinical study while using mist and mask as part of a bleaching treatment. Results may vary depending on hair type, quality and history.

Water (Aqua) (Eau), Alcohol Denat., Propylene Glycol, Cetearyl Alcohol, Dicaprylyl Ether, Cetyl Esters, Behentrimonium Chloride, Polysorbate 20,sh-Oligopeptide-78 (K18Peptide™), Hydrolyzed Wheat Protein, Hydrolyzed Wheat Starch, Isopropyl Alcohol, Tocopherol, Phenoxyethanol, Potassium Sorbate, Citric Acid, Fragrance (Parfum), Geraniol, Linalool, Hexyl Cinnamal, Benzyl Alcohol.

Description

A leave-in treatment mask for all hair types that clinically reverses damage in 4 minutes. The patented peptide technology works to repair damage from bleach, color, chemical services & heat – restoring strength, softness, smoothness, and bounce to hair.

what you can expect
by damage type

backed by science,
loved by stylists
Our community of stylists and colorists believe K18 is liberating hair—no matter the hair type or generation.
“K18 allows me to go everywhere I want to go with my color work and the end result is my guests get to be bright and shiny and healthy.”

– Christine Thompson, Director of Color at Spoke & Weal
got questions?
Get started here
When hair gets damaged, the polypeptide chains (keratin chains) that make up the inner structure of hair strands become weakened and break. For context, there are billions and billions of polypeptide chains (keratin chains) in a single strand of hair. When these are damaged, hair’s core structure responsible for elasticity and strength becomes compromised and as a result it loses its resiliency and shine—or the look and feel of healthy hair.

After spending a decade in the lab scanning and testing all amino acid sequences across the entire keratin genome that makes up human hair searching for a breakthrough, we discovered one unique sequence (a bioactive peptide) that brings damaged hair back to its original, youthful state. This is our K18Peptide™.

Traveling deeper into the inner layers of hair than traditional repair products, our revolutionary peptide is just the right size and makeup to fit in and reconnect those broken polypeptide chains (keratin chains). And because our peptide is a bit of an overachiever, as a result of this reconnection, any disturbed disulfide bonds are also re-conformed.

Our peptideemploys biomimetics to get the job done. To put it simply: Biomimetics is the practice of learning from and mimicking nature. Mimicking the natural structure of keratin building blocks (amino acid sequences), our K18 bioactive peptide is recognized as natural by the hair. It’s not washed away by water or shampoo like traditional bonding agents either, making K18 a genuine, lasting solution for damaged strands.
Our patented peptide is a unique sequence of amino acids that travels deep into hair’s core structure to fit in and reconnect broken polypeptide chains (keratin chains) responsible for hair strength and elasticity.

An Analogy: When building proteins, the order of the amino acids determines the kind of protein and its properties, much like the way letters are arranged to make meaningful words and sentences. In the same way the order and where each word sits in a sentence leads to its overall meaning, K18 is the magic word that fits right in, integrating itself with the keratin chains as the hair recognizes it as a natural building block.
K18 is most effective on clean, towel-dried hair. Conditioners use silicones and conditioning agents that form heavy coatings on hair , preventing our peptide from reaching the broken polypeptide chains deep inside hair’s inner layer.
We like to keep our formulas minimal, only using the exact amount of ingredients needed to get the peptide where it needs to go. Our unique blend of 3 alcohols function to open up the hair cuticle so the K18Peptide ™ can penetrate the inner most layer of hair, reaching the broken polypeptide chains (keratinchains). Here the alcohol serves as an agent to optimize the hair environment for K18 to work on a deeper level.
You will start to see stronger, softer, healthier hair after just one use.

Renews strength, softness, smoothness, and bounce

K18 strengthens hair’s core structure, restoring damaged curl patterns and leaving strands looking and feeling like new.
K18 reconnects broken keratin chains, restoring hairs elasticity and strength meaning coily hair can be renewed and brought back to its original springy, healthy shape.
K18 restores strength, softness, smoothness, and bounce so even the sleekest hair can feel like new.
4.7
Rated 4.7 out of 5 stars
Based on 8,129 reviews
8,129 reviews
  • Kaitlyn S.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Color-care, Frizz, Dryness, Split-Ends
    Hair Type Fine/Thin
    My Results Visible Difference, Stronger Hair, Soft Touchable Hair
    Rated 5 out of 5 stars
    21 hours ago
    I was so happy to finally splurge on the jumbo size

    It helps when used as directed and saveds me some time as I dont have to deep condition . No complaints although it's hard to tell how "bad" or "good" my hair is. I am coming back from the sample to buy the astro lift tho it seems to really give some umph!

    K Profile picture for K18Hair
    K18Hair
    13 minutes ago

    Thank you for your review!

  • Karen M.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 35 - 44
    Hair Concern Dryness, Split-Ends, Fragile/brittle hair, Chemical damage, Heat damage
    Hair Type Fine/Thin
    My Results Visible Difference, Less Frizz, Less Breakage, Stronger Hair, Smoother Hair
    Rated 5 out of 5 stars
    5 days ago
    Love it

    My hair is extremely thin and fine and has tons of damage and breakage. My ends were like straw. I decided to try this based on Abby's recommendation from YouTube. I used it 4 times in a row and now use it once a week. I do think I'm seeing results as my ends are looking better. It's expensive but a little goes a long way and while it's still a little early, I'd say it's worth it. Before and after pic included.

    K Profile picture for K18Hair
    K18Hair
    3 days ago

    Thank you Karen! Yes less is more!

  • Fee B.
    Verified Reviewer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Split-Ends, Dryness, Frizz, Color-care, Chemical damage
    Hair Type Medium Density, Straight/Wavy
    My Results Less Frizz, Visible Difference, Smoother Hair, Soft Touchable Hair, Shinier Hair
    Rated 5 out of 5 stars
    1 week ago
    AAMAZING!!!! AAMMAAZZIINNGGG!!!!!!!!! AAMMAZZINNGGGG!!!!!!

    I was honestly very scared to use, especially not rinsing and conditioning. Because usually other products have you wait 10 minutes and rinse and condition. All my other products I WILL BE THROWING AWAY!!!!!! THIS PRODUCT IS A MUST HAVE. Last night was my first time using it.. i have DEFINITELY NOTICED A BIG CHANGE in my bleached hair with one use!!! I first used the Damage K18 shampoo, then 2 pumps of this GOD SENT PRODUCT LEAVE IN MOLECULAR REPAIR HAIR MASK, then used the k18 hair oil and blow dryed. And i have never ever noticed such A DRAMATIC CHANGE IN MY HAIR!!!!! I have been missing out all this time. Especially because it took me 5 years to go completely bleach blonde and I could've been using this product all along. I KNOW ITS PRICEY (FOR ME A SINGLE MOM IT IS VERY EXPENSIVE) BUT IT IS WELL WORTH IT, I NEED A LIFETIME SUPPLY. Thank you K18 for such an amazing bomb product. Definitely a 20 star product. Can't wait to see my hair results after 6 times of using it!!!!!!!!!!!!!

    K Profile picture for K18Hair
    K18Hair
    1 week ago

    We appreciate your 20-star review! Thank you Fee!

  • Amanda W.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Heat damage, Color-care, Fragile/brittle hair, Split-Ends
    Hair Type Medium Density, Fine/Thin
    My Results Less Frizz, Visible Difference, Stronger Hair
    Rated 5 out of 5 stars
    3 weeks ago
    Wonderful product!

    Great product, does what it says and more! I love using this intermittently after hair color.

    K Profile picture for K18Hair
    K18Hair
    2 weeks ago

    Thank you Amanda!

  • Brooke Z.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Heat damage, Chemical damage, Frizz, Split-Ends
    Hair Type Medium Density
    My Results Less Breakage
    Rated 5 out of 5 stars
    3 weeks ago
    Love the leave in conditioner!

    Product is great!

    K Profile picture for K18Hair
    K18Hair
    3 weeks ago

    Thank you for your review!

recommended products
Pro Distribution Partners

Paramount Beauty Supply
USA
Salon Services Pro
USA
Salon Service Group
USA
Salonwax Pro
USA
Premier Beauty Supply
USA
Launching Soon
Ozdare - Australia
AU
 
Launching Soon
American Crew Ltd. - New Zealand
NZ
 
Launching Soon
PlayGround - Hong Kong
HK
 
Launching Soon
Session Map - Sweden
SE
 
Launching Soon
Cyprus
CY
 
Launching Soon
Belgium
BE
 
Coming Early 2021
Canada
CA
 
Coming Early 2021
Czech Republic
CZ
 
Coming Early 2021
Finland
FI
 
Coming Early 2021
France
FR
 
Coming Early 2021
Germany
DE
 
Coming Early 2021
Ireland
IR
 
Coming Early 2021
Italy
IT
 
Coming Early 2021
Netherlands
NL
 
Coming Early 2021
Norway
NO
 
Coming Early 2021
Singapore
SG
 
Coming Early 2021
Taiwan
TW
 
Coming Early 2021
UK
UK
 
Coming Early 2021
thank you for visiting!

You are now being redirected to an official partner website for this region where you can shop K18 Hair.

Changed your mind? Go back.

00:00
subscribe + save 15%
healthy hair on your schedule
Pick your K18 + how often you want to replen.
We’ll send you a heads up before every delivery.
You’re in charge. Change the way you pay, skip a shipment, or cancel anytime.
Blackfire Tracking