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full-size leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage
Rated 4.6 out of 5
Based on 7114 reviews

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥 

*Disclaimers

Repairs Damage Caused By

  • Bleach + Color Bleach + Color
  • Heat Heat
  • Chemical Services Chemical Services
OR
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more to know

  • K18PEPTIDE™ is a biotech-developed peptide that mimics hair's structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during bleaching, color and chemical services + heat*.

  • pH-optimized (5.0-6.0) to help minimize cuticle swelling + put hair proteins in their most resilient state

  • Cream format enables easy, lightweight application across all hair types, with detangling and softening benefits

  • Vegan, color-safe, cruelty-free

key benefits

Takes damage repair further – reconnects both polypeptide chains (and as a result, also reconnects disulfide bonds) for strength along the length + width of the hair - offering comprehensive, lasting damage repair

Restores hair from even extreme damage - by working at the innermost layer of the hair, core strength and elasticity are renewed for strong, smooth, bouncy hair

Delivers immediate and lasting results – hair is repaired from the first use and lasts past your next wash, for ongoing reparative benefits

Simplified repair - convenient, leave-in formula works in just 4 minutes, with no extra rinse required

Works on all hair types – because K18PEPTIDE™ works on a molecular level (where all hair is the same), this product is effective on all hair types

how to use

  1. Shampoo, do not condition. Towel-dry thoroughly
  2. Apply 1-3 pumps of K18 leave-in molecular repair hair mask based on your length and density, starting at the ends and working up towards the roots
  3. Let sit for 4 minutes. Do not rinse out
  4. Comb, add product + style as usual. Use for 4-6 washes post-salon service, then as needed

dos and don'ts

  • DO clarify before K18 if you’re a heavy product user (demineralize for mineral + metal buildup)
  • DO apply on clean, damp hair
  • DO wait the full 4 minutes before combing or styling
  • DO add whatever styling products you love after the 4 minutes
  • DO use for 4-6 shampoos consecutively for progressive results
  • DON'T use conditioner before applying K18 Mask (you can apply after the 4 min but most find they don’t need it)
  • DON'T overdo it—less is more
  • DON'T rinse it out

ingredients

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.

pairs well with
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Rated 4.7 out of 5
Based on 229 reviews
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PEPTIDE PREP™ detox shampoo

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Description

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥 

*Disclaimers
Image Comparison Drag Handle
see molecular repair in action
The K18 leave-in molecular repair hair mask delivers lasting + progressive results, for healthier hair with each use.

the experts know

Groundbreaking PRO stylists, scientists + beauty experts have unlocked new levels of expression with K18 molecular repair.

got questions?

Get started here.

how does the k18 mask work?

The K18 mask works as a treatment to reverse damage in 4 minutes. It’s powered by our biomimetic K18PEPTIDE™ to seamlessly fit in and reconnect broken polypeptide chains at the molecular level. As a result, disulfide bonds are also reconnected for reinforced strength along the length + width of hair—offering comprehensive, lasting, and progressive repair.

what is the k18peptide™?

K18PEPTIDE™ is a biotech-developed peptide that mimics hair’s structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during damage from bleach + color, chemical services, and heat*
*Disclaimers

why skip conditioner?

Conditioner leaves a film that blocks our peptide from penetrating effectively. Once the 4-minute wait time is up, feel free to use a conditioner, a leave-in, or any type of product.

i noticed there’s alcohol in the formula, isn’t that bad for you?

We like to keep our formulas minimal, only using the exact amount of ingredients needed to get the peptide where it needs to go. Here the alcohol serves as an agent to optimize the hair environment for the K18 mask to work on a deeper level. Our unique blend of 3 alcohols functions to open the hair cuticle so the K18PEPTIDE™ can penetrate the innermost layer of hair, reaching the broken polypeptide chains (keratin chains).

when should i expect to see results?

Most see results after 2-3 uses. The more damaged the hair, the more dramatic the results so it may vary depending on your hair type and level of damage.
reviews
average rating 4.6 out of 5
Based on 7114 reviews
  • 5 Stars
    5808 Reviews
  • 4 Stars
    669 Reviews
  • 3 Stars
    293 Reviews
  • 2 Stars
    138 Reviews
  • 1 Star
    206 Reviews
92% of reviewers would recommend this product to a friend
Customer photos and videos
7114 Reviews
Reviewed by Kelly S.
Verified Buyer
I recommend this product
Age
45 - 54
Hair Concern
  • Chemical damage
  • Split-Ends
  • Fragile/brittle hair
Hair Type
  • Fine/Thin
My Results
  • Less Breakage
  • Visible Difference
  • Less Frizz
Rated 5 out of 5
Review posted

I can’t live without it now!

This stuff is amazing. I have super fine hair and get split ends very easily K18 and has changed my hair.. my ends are strong so my hair grows longer. I love it. I use it 3 times per week.

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Reviewed by Ioana C.
Verified Buyer
I recommend this product
Age
25 - 34
Hair Concern
  • Frizz
  • Fragile/brittle hair
  • Dryness
  • Split-Ends
Hair Type
  • Thick/Coarse
My Results
  • Less Frizz
  • Visible Difference
  • Smoother Hair
  • Soft Touchable Hair
  • Shinier Hair
Rated 5 out of 5
Review posted

Best leave in hair repair mask I've ever tried!

I have coarse, color treated hair and this mask works like a charm to soften, repair, and tame any frizz or damaged hair. 10/10 would recommend.

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K18Hair

Yay for soft and tamed hair! Thank you for your review Ioana!

Reviewed by Christine S.
Verified Reviewer
I recommend this product
Age
45 - 54
Hair Concern
  • Chemical damage
  • Heat damage
  • Fragile/brittle hair
  • Dryness
  • Split-Ends
Hair Type
  • Thick/Coarse
  • Straight/Wavy
My Results
  • Visible Difference
  • Stronger Hair
  • Less Breakage
  • Soft Touchable Hair
  • Bouncy Hair
Rated 5 out of 5
Review posted

Amazing

I didn’t know what to expect when trying this out but I am amazed. I take very good care of my hair… hair oiling, massage, good products. I’ve got some damage still from a bad highlight session (split ends and brittle/weak ends)

I’ve used this once and WOW! My split ends look better, my hair is already stronger and feels soft (no more crackle when I run my fingers thru it). This is like crack for your hair. I am super impressed and will definitely continue to use as directed.

Tip: my hair is course, thick and wavy. I paired this with my fav leave in conditioner and oil for my ends after the 4 min for extra protection and conditioning

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K18Hair

Love the tip! Thank you for your review Christine!

Reviewed by Jill
Verified Reviewer
I recommend this product
Age
35 - 44
Hair Concern
  • Heat damage
  • Frizz
  • Fragile/brittle hair
  • Split-Ends
  • Dryness
Hair Type
  • Fine/Thin
My Results
  • Visible Difference
  • Stronger Hair
  • Smoother Hair
  • Soft Touchable Hair
  • Less Frizz
Rated 5 out of 5
Review posted

Game changer

My hair was severely damaged from over processing and almost daily use of heat tools. At almost 40, I never thought I could have amazing feeling and looking hair again from years of “abuse” on my hair. I went to get my hair done at my salon and my stylist recommended using it and I said “why not!” This is the first product I have used that ACTUALLY works. I’ve used it 3-4 times now since the first use and my hair went from feeling like stiff hay to soft, strong and full! I absolutely love it. It’s a tad pricy but worth every penny.

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K18Hair

Yay for soft and strong hair! Thank you for your review Jill!

Reviewed by Savannah B.
Verified Buyer
I recommend this product
Age
35 - 44
Hair Concern
  • Chemical damage
  • Heat damage
  • Color-care
  • Frizz
  • Fragile/brittle hair
Hair Type
  • Fine/Thin
My Results
  • Less Frizz
  • Stronger Hair
  • Less Breakage
  • Smoother Hair
  • Soft Touchable Hair
Rated 5 out of 5
Review posted

Amazing

This product is so amazing! It has helped my hair so much already! I definitely recommend this! I have a before picture where my hair is really thin and breaking off! Then I have an after picture that’s showing regrowth and it’s looking and feels so much better!

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K18Hair

Wow your hair looks amazing! Thank you for your review Savannah!

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