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4.7
Rated 4.7 out of 5 stars
8,199 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 8,199 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
8,199 reviews
  • Julia T.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 25 - 34
    Hair Concern Chemical damage, Heat damage, Fragile/brittle hair, Split-Ends, Oily hair/scalp
    Hair Type Fine/Thin
    My Results Visible Difference, Stronger Hair, Less Breakage
    Rated 5 out of 5 stars
    2 hours ago
    Absolutely favorite

    I bought my first bottle at HongKong Sephora back in March. I wasn’t sure how good it’s gonna be since I was recommended by AI. I have thin/fine hair, and I bleach it to blonde every 3 months. I always had a hard time growing my hair long cause it’s so damaged. Nothing I tried worked!!!! Not even the products recommended by my hairstylist.

    KU Profile picture for K18Hair UK
    K18Hair UK
    56 minutes ago

    Thank you so much, Julia! 💛 We're thrilled the Jumbo Leave-In helped where nothing else worked for your bleached hair. Your trust means everything to us! ✨

  • Shannon B.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 35 - 44
    Hair Concern Chemical damage, Heat damage, Frizz, Fragile/brittle hair, Dryness
    Hair Type Fine/Thin
    My Results Less Breakage
    Rated 5 out of 5 stars
    14 hours ago
    It worked

    It seems to have made a difference in breakage

    KU Profile picture for K18Hair UK
    K18Hair UK
    14 hours ago

    Thank you for your wonderful review, Shannon! We're so thrilled to hear that the Jumbo Leave-In Molecular Repair Hair Mask is making a real difference in reducing breakage for you. That's exactly what we love to see - our molecular repair technology working to strengthen and protect your hair from the inside out.

    It's so rewarding to know that K18 is helping improve the health of your hair. Thank you for choosing us and for taking the time to share your experience!

  • Jayne B.
    Verified Buyer
    Reviewing
    Leave-In Molecular Repair Hair Mask Sample
    I recommend this product
    Rated 5 out of 5 stars
    2 days ago
    Excellent

    Really good product my hair has never felt better , I would recommend 100 percent , I am 53 years old and my hair isn’t what it used to be but with K18 treatment and the oil it’s made a world of difference.

    KU Profile picture for K18Hair UK
    K18Hair UK
    Yesterday

    Thank you for your wonderful review, Jayne! 💛 We're absolutely thrilled to hear that K18 has made such a world of difference for your hair. It's so rewarding to know that the Leave-In Molecular Repair Hair Mask Sample, along with our hair oil, has helped your hair feel better than ever!

    We love that you're experiencing these amazing results - that's exactly what we hope for with every K18 product. Thank you for the 100% recommendation and for taking the time to share your experience with us. Your support means the world to us!

  • Melanie G.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Chemical damage, Heat damage, Fragile/brittle hair, Split-Ends
    Hair Type Fine/Thin
    My Results Shinier Hair, Smoother Hair, Soft Touchable Hair, Visible Difference, Stronger Hair
    Rated 5 out of 5 stars
    3 days ago
    Love this stuff!

    I'm trying to grow out my natural hair which I used to bleach, and this stuff has been a total miracle product! Transitioning away from bleach is usually a nightmare of breakage and split ends, but since adding K18 to my routine, I’ve noticed a massive difference. It actually makes my hair feel stronger, healthier, and way more resilient. It’s significantly cut down on the snap-and-breakage I used to get, allowing me to finally retain some length.

    KU Profile picture for K18Hair UK
    K18Hair UK
    3 days ago

    Thank you for sharing your experience, Melanie! We're thrilled to hear K18 has helped strengthen your hair and reduce breakage during your transition from bleaching. Your hair health journey means so much to us!

  • Pearl D.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Chemical damage, Heat damage, Color-care, Frizz, Fragile/brittle hair
    Hair Type Curly/Coily
    My Results Visible Difference, Less Breakage, Stronger Hair, Defined Curl/Wave Pattern, Cleaner, fresher hair
    Rated 5 out of 5 stars
    4 days ago
    Can’t live without

    Helps my blonde hair so much

    KU Profile picture for K18Hair UK
    K18Hair UK
    4 days ago

    Thank you Pearl! We're so happy to hear our Leave-In Molecular Repair Hair Mask has become essential for your blonde hair. Your support means everything to us!

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