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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 7456 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
  • Heat
  • 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

K18 molecular repair hair oil

Rated 4.7 out of 5
Based on 427 reviews
Weightless oil that strengthens, repairs damage + reduces frizz View Molecular Repair Hair Oil product

PEPTIDE PREP™ detox shampoo

Rated 4.8 out of 5
Based on 262 reviews
Color-safe, non-stripping clarifying shampoo with the K18PEPTIDE™ View PEPTIDE PREP™ detox shampoo 8.5oz product

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

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.
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healthier hair with every use
Reverse damage in 4 minutes with our breakthrough K18 molecular repair technology.

the K18 difference

Feel what’s possible with fewer steps, less waste + less time.
efficacy
patented K18PEPTIDE™ powers deeper + lasting repair.
simplicity
fewer steps for a streamlined routine.
speed
results in one 4-minute use.

how molecular repair compares

how K18 works

Traveling into the innermost layers of hair, our K18PEPTIDE™ renews strength along the width AND length of hair for lasting strength where it matters.

feel what's possible with K18

See how K18 unlocks our community's expression
reviews
average rating 4.6 out of 5
Based on 7456 reviews
  • 5 Stars
    6101 Reviews
  • 4 Stars
    681 Reviews
  • 3 Stars
    305 Reviews
  • 2 Stars
    146 Reviews
  • 1 Star
    223 Reviews
92% of reviewers would recommend this product to a friend
Customer photos and videos
7456 Reviews
Reviewed by frances d.
Verified Buyer
I recommend this product
Age
55 - 64
Hair Concern
  • Frizz
  • Chemical damage
  • Color-care
  • Dryness
  • Fragile/brittle hair
Hair Type
  • Thick/Coarse
  • Grey Hair
  • Curly/Coily
My Results
  • Less Frizz
  • Smoother Hair
  • Soft Touchable Hair
  • Shinier Hair
  • Less Breakage
Rated 5 out of 5
Review posted

Incredible!

This product, it's very hard to describe. It is absolutely amazing!

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K18Hair

We appreciate your review Frances!

Reviewed by Blanca A.
Verified Buyer
I don't recommend this product
Age
45 - 54
Hair Concern
  • Frizz
Hair Type
  • Curly/Coily
Rated 1 out of 5
Review posted

Bad product

The worst product I've ever bought is not worth buying, too expensive for the size

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K18Hair

We are sorry that you are not loving your K18. Reach out to us to troubleshoot to Hello@K18Hair.com.

Reviewed by Nancy S.
Verified Buyer
I recommend this product
Age
65+
Hair Concern
  • Color-care
  • Dryness
Hair Type
  • Medium Density
  • Curly/Coily
My Results
  • Visible Difference
  • Smoother Hair
  • Shinier Hair
Rated 4 out of 5
Review posted

Hair Repair

Left my hair shiny and healthy.

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K18Hair

Thank you Nancy for your review!

Reviewed by Melanie D.
Verified Buyer
I recommend this product
Age
55 - 64
Hair Concern
  • Fragile/brittle hair
  • Frizz
  • Heat damage
  • Chemical damage
  • Split-Ends
Hair Type
  • Fine/Thin
My Results
  • Less Frizz
  • Visible Difference
  • Less Breakage
  • Smoother Hair
  • Shinier Hair
Rated 5 out of 5
Review posted

One use

I’m always skeptical about people saying how wonderful a product is after one use. My hair breaks easily and gets frizzy ends. I used this one day and let my hair air dry. I could tell right away it was smoother. The next day I straightened my hair and there was not any breakage to be seen and no frizz. I am now on day 5 hair and it looks as good as day one. I will not use another mask again but this.

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K18Hair

Thank you Melanie for your review!

Reviewed by Lisa R.
I recommend this product
Age
45 - 54
Hair Concern
  • Heat damage
  • Dryness
  • Split-Ends
  • Chemical damage
  • Fragile/brittle hair
Hair Type
  • Medium Density
My Results
  • Less Frizz
  • Visible Difference
  • Stronger Hair
  • Less Breakage
  • Soft Touchable Hair
Rated 5 out of 5
Review posted

Worth every penny!

It is incredible! I had my hair completely damaged from over processing and hot tools. The pictures attached are after four washes. I wash my hair twice a week and was trying not to do anymore damage with the blow drying. I also didn’t want to cut my hair and have bangs . A hairstylist friend recommended this stuff and I bought it. People complain about the size of the bottle but it’s worth it. You don’t need to use but one to two pea size pumps on bangs. Also I would warm up in my fingers before applying. I heard that in a review and feel like it made a difference. When you are first using it depending on the amount of damage it felt thick but hydrating. At the fourth wash it felt hydrated and manageable. Be patient but it works. They say six wash is when you really see results. I can’t wait!!!

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K18Hair

Better with time. Thank you Lisa for your review!

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