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4.7
Rated 4.7 out of 5 stars
8,027 Reviews

full-size leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage

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

Repairs Damage Caused By

  • Bleach + Color
  • Heat
  • Chemical Services
  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.
  • 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.

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.

  • 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.

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.

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Color-safe, non-stripping clarifying shampoo with the K18PEPTIDE™

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.
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.
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*

*k18hair.co.uk/disclaimers
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.
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).
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.
powered by K18PEPTIDE™

Biomimetic peptide clicks into hair’s keratin structure—the source of core strength—for soft, shiny, bouncy results that won’t wash away.

how to use molecular repair mask
1. Shampoo, do not condition. Towel-dry thoroughly.

2. Apply 1-3 pumps 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 styling product + style as usual. Use for 4-6 washes, then as needed.
feel what's possible with K18
See how K18 unlocks our community's expression
4.7
Rated 4.7 out of 5 stars
Based on 8,027 reviews
93%would recommend these products
Reviews Summary
Customers say this hair mask transforms damaged, bleached, and chemically-treated hair, making it softer, stronger, and more manageable. Many report significant improvements in hair texture, with reduced breakage, split ends, and frizz. Users with curly hair find it enhances curl definition and reduces dryness. The lightweight formula doesn't weigh hair down or leave residue. Many reviews mention it works particularly well for bleached hair, helping restore smoothness and shine. Some note the price is high but find it worthwhile since only small amounts are needed per use.
Customers Talked About
8,027 reviews
  • Shannon W.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Color-care, Heat damage
    Hair Type Thick/Coarse, Medium Density
    My Results Stronger Hair, Less Breakage, Smoother Hair, Shinier Hair
    Rated 5 out of 5 stars
    1 hour ago
    Love K18

    I’m at hairstylist in K 18. Tina has been a complete game changer for me. I use it on myself and I am completely loving the results. I’m using the hair oil to leave in restructuring cream and the shampoo and conditioner and have had absolutely wonderful results. my hair is so silky brought the shine back instantly right after I had highlighted my hair, which usually takes a couple weeks for it feel healthy again.

  • Diane D.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Rated 5 out of 5 stars
    Yesterday
    K18 excellent product

    I have been using this product and have found it to be excellent. My hair styles much better with less ‘fly away’ hair and less breakage

  • Jency
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Frizz, Dryness, Fragile/brittle hair
    Hair Type Curly/Coily, Straight/Wavy
    My Results Less Frizz, Bouncy Hair, Visible Difference, Defined Curl/Wave Pattern, Smoother Hair
    Rated 5 out of 5 stars
    Yesterday
    My curls are back

    I had the mini one and forgot bout it. Used it again today after like 2 months… and well this is my hair after it dried fully. Normally its VERY frizzy.

    KU Profile picture for K18Hair UK
    K18Hair UK
    3 minutes ago

    We're so thrilled to hear about your amazing results with the Full-Size Leave-In Molecular Repair Hair Mask, Jency! It sounds like rediscovering this product after 2 months was such a wonderful surprise - there's nothing quite like that feeling when you see your natural curl pattern come back to life and the frizz just melts away.

    We love hearing stories like yours where customers reconnect with products that truly transform their hair. It's incredible how the molecular repair technology can help restore your curls to their beautiful, defined state. Thank you so much for sharing your experience - it really means the world to us to know that our mask is helping you embrace and love your natural texture!

  • Ceara D.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Color-care, Frizz, Split-Ends
    Hair Type Fine/Thin
    My Results Visible Difference, Less Breakage, Defined Curl/Wave Pattern, Stronger Hair
    Rated 5 out of 5 stars
    6 days ago
    Amazing

    This product has completely changed my hair! As I have pcos and thyroid issues I lose a lot of hair. I started using this product 3 years ago. I started with once a week then twice a week now I use it every time I wash my hair! This product had been a life saver for me. My hair feels so soft and the frizz has also cut down. I can tell major difference when I don’t use it! I could rent and rave for hours but just buy a trial size and try it! You will not turn back. I also have eczema on my scalp it is one of the few products I can use that does not cause a flare up!

    KU Profile picture for K18Hair UK
    K18Hair UK
    5 days ago

    Thank you so much for this incredible review, Ceara! We're absolutely thrilled to hear that the Mini Leave-In Molecular Repair Hair Mask has been such a life changer for you over the past 3 years - that kind of loyalty and transformation story means the world to us! It's wonderful that you've found your perfect routine with it and that you're experiencing such amazing results with softer hair and reduced frizz. We're also so grateful that it's gentle enough for your sensitive scalp - we know how important that is! The fact that you can tell a major difference when you don't use it really shows how effective our molecular repair technology is. We're so excited that you're loving the product and thanks for your amazing 5-star review and recommendation! 💛

  • nagaumasowmya v.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Dryness, Fragile/brittle hair
    Hair Type Fine/Thin
    My Results Less Frizz, Less Breakage, Visible Difference, Smoother Hair, Shinier Hair
    Rated 5 out of 5 stars
    1 week ago
    Best product ever

    Instantly gave hydration and smoothness to my hair and its holygrail for my haircare routine

    KU Profile picture for K18Hair UK
    K18Hair UK
    5 days ago

    Thank you so much for this incredible review! We're absolutely thrilled to hear that the Jumbo Leave-In Molecular Repair Hair Mask gave you instant hydration and smoothness - that's exactly what we love to hear! It's amazing that it's become your holy grail for your haircare routine. We're so excited that you're loving the results and thanks for your fantastic 5-star review! ✨

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