Name: K18 Leave-In Molecular Repair Hair Mask
Brand: K18
Rating: 85.0 (15 reviews)

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Dr. Jenny Liu

315k subs · 6k devotees

✓Approved

"I will add in probably you know in that routine like once a week a bond repair treatment like K18 or something like that."

Top Pick: peptide bond repair treatment

All 7 takes from Dr. Jenny Liu

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"I will add in probably you know in that routine like once a week a bond repair treatment like K18 or something like that."

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"The one product that I keep getting from Sephora over and over again is the K18 Leave-In Molecular Repair Hair Mask. I love the fact that it comes in different sizes now, so if you're not willing to take this splurge -- because it's not cheap -- you can try a smaller size or restock on the travel size. But this is literally the peptide bond repair treatment that has turned my hair around. I really love the science. It's got this unique peptide that penetrates your hair, and you can use it different ways. Before, I would use it as a leave-in mask after shampooing -- I don't condition -- then come out of the shower, apply this, wait 4 minutes, and follow it with my styling products. For some people who find that not moisturizing enough, you can use it as an in-shower treatment: leave it on for 4 minutes, rinse it off, and follow with your traditional conditioner and the rest of your routine. I also find that when you use it more regularly in the beginning, you can space out your treatments. Now I only use it maybe a few times a month. But yes, this is the repair product that has completely changed my hair. Highly recommend it if your hair is damaged, over-processed, or over-colored -- this is the one to try."

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"Apply a pump or more depending on the length of your hair to your entire hair and wait for 4 minutes before applying other styling products. This not only helps repair but conditions your hair at the same time. Compared to other hair repair treatments, I personally have had the most noticeable improvement in my hair when I use this consistently. You can use it like once a week or a couple of times a week. It's certainly pricey, but it's a great one to buy during savings events. It's a really rich, dense hair mask that is not overloaded with protein, which I appreciate because some individuals are protein sensitive and a lot of protein can build up and weigh down your hair. This is more rich in plant-derived extracts and oils that are nourishing and conditioning, and you definitely do not feel your hair is weighed down afterwards."

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"K18 is probably one of my favorite hair care lines from Sephora and really has wonderful science behind their formulation. I use it regularly and it's really a line designed to help repair chemically processed damage hair from coloring, heat styling, frizzy hair, and breakage. This set contains their popular K18 Leave-In Molecular Repair Hair Mask along with the miniature hair oil, and basically both products contain their signature K18 peptide that's been shown to really get into the hair to help temporarily strengthen and repair hair, and over time actually has been shown to really make that more permanent change to helping reduce hair breakage. I also love the hair oil because a few drops go a long way and really helps to act as a heat protectant, helps to smooth down hair, reduce frizz, and also has avocado oil that helps to soften and nourish hair at the same time."

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"After washing, I apply that treatment as a treatment and leave-in conditioner in one and I don't feel that I need any additional conditioning afterwards. This K18 treatment is really one of the best things I've done for my hair when it comes to bond repair treatment. It really has turned my hair around from all the coloring and chemical processing and heat styling. You can use it once a week, but in the beginning you can definitely use it more consecutively, like up to four times, to really get that good result. If your hair still needs more conditioning after using it, you can rinse it off after four minutes when that bond repair has fully penetrated into your hair and then condition if you need to, but I personally don't need to do that."

Dermatologist’s tips on How to minimize hair breakage | Dr. Jenny Liu

"K18 leave-in molecular repair hair mask is one of the key products that have transformed my hair. I use this quite a bit in 2023 and throughout 2024 and I do feel like ever since I started using it I have noticed a significant difference in the overall quality and health of my hair. The reason why I love this is because it's worked really well and really it's the convenience of use that's probably really why I've used it so much. This does have really cool science behind it and the people that developed this product come through kind of a library of all the peptides that we know kind of affiliated with hair."

Dermatologist updated Haircare routine | Dr. Jenny Liu

"K18 leave-in molecular repair hair mask I've been using for the past two years now and it has made the biggest difference for my hair and the structural component of my hair. This is a leave-in conditioner so what you do is you wash your hair shampoo your hair and then you apply this mask from root to the end and then after 4 minutes you can apply or style your hair as usual. You can use this on a daily basis like four times a week until your hair gets to a good point and then use it as needed. At this point I probably use it like once a week. When I was really aggressively trying to repair my hair I was probably using it maybe two to three times a week but I feel like it has definitely made the biggest difference for me. It's nice because it not only works like a leave-in conditioner so helps to instantly soften reduce frizz help to detangle make your hair manageable but over time it does do wonders for your hair if you have like me like brittle dry damaged hair."

Sincerely Miss Ash

194k subs · 3k devotees

✓Approved

"This is a must in my hair care routine. It really helps to strengthen and repair the bonds of your hair. Because I'm blonde, I feel like this is a must for me personally. If my hair appointment is coming up, I will use this about two times before my hair appointment just to strengthen my hair. And then post hair appointment, I will use this six hair washes post hair treatment to really strengthen and repair my hair from getting my hair highlighted. Ever since doing this technique, and I've been doing this now for over a year, I've noticed a big difference with my hair. My hair actually grows, my hair doesn't break, and it really keeps my hair strong and healthy looking. My hair isn't frizzy either. It really has improved my hair. Just be patient with this and use it and be consistent. Within a couple of months, you really should see a difference with your hair. You don't need to use this every day. You may want to use this a couple of times per month. It really just depends on you. I put about a pump, a pump and a half into my palm. This was the collaboration with Future Society, which is a limited edition scent. It smells so good, it smells way better than the original K18 Leave-In Molecular Repair Hair Mask. I really hope that they keep it long term because it's really nice."

All 7 takes from Sincerely Miss Ash

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"I've been using this now for pretty much two years, and this is the one product that has honestly transformed my hair. It has brought the health back, it makes the ends of my hair a lot stronger, and it does a really good job to repair damaged hair as well. I usually use this as maintenance throughout the month. I don't use it every time I wash my hair, but if I have a hair appointment coming up, I will be consistent with it for the first two to three washes before my appointment. And then after I've had my hair highlighted, I will use it for the next six washes post-appointment to really strengthen the ends and just bring the health back to my hair. Ever since I've been doing that, I've noticed a big difference. My hair is just shinier, softer, it looks a lot healthier, and it really is coming from this product. I usually do two pumps, and you want to warm it up in the palms of your hands until your hands are white, then apply it to your hair. I focus mainly on mids to ends and my bangs because those are generally the areas that can be a little drier and a little more frizzy."

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"I apply it to mids to ends and I apply it in my bangs and I leave it in my hair for like 5 to 8 minutes, maybe 10. Then I rinse it out and my hair just feels so silky. It really makes a big difference. The K18 Leave-In Molecular Repair Hair Mask is a non-negotiable. This will truly transform your hair. I have been very consistent with this over the last year, year and a half, and I have truly seen a big difference with my hair. I have been through the ringer with my hair. I've dealt with a lot of breakage and dryness several years ago, and my hair is starting to look and feel so much better. And I really do feel like the K18 brand has really made my hair become the way it looks now. Especially this product right here. After you've done your hair care routine in the shower and you hop out of the shower, towel dry your hair and then put maybe one or two pumps of this in your hair. I will do this maybe once a week, once every other week. But if I just got my hair done and I just got highlights, I will use the K18 mask every hair wash for the next six hair washes to strengthen the ends to bring that shine and health into my hair. And this is where I have noticed a big difference with my hair."

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"This is the K18 Leave-In Molecular Repair Hair Mask. This really does work to repair damaged hair and to repair the bonds of your hair. I like to use this sometimes several hair washes in a row and then I might take a break for a few weeks and then start back up again. This is a great product to use even after your hair appointment just to strengthen your ends, especially if you've noticed that you have a little bit of damage or maybe your hair's feeling a little dry. This is incredible and it really does make your hair super soft and shiny, and eventually with consistency, like this can totally repair the hair and make it look healthy. I will be purchasing another one because I feel like this does the job really well."

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"Since being really consistent with K18, honestly, this has really improved my hair. And then after the six hair washes, I'll take a break for a while. And then just before I go back to the hair salon again, I will use this one or two times just to strengthen my hair up again. This really is gamechanging whether you have blonde hair or not. This can really improve the bonds and I love it. Every time there's a sale, I always stock up."

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"This is a must-have. This is a product that actually works. That is worth the money. This is a product that will help to repair damaged hair. It helps to strengthen the bonds of your hair and it also helps to add shine and keeping your hair looking as healthy as possible. After I've just had my hair colored I like to use the K18 Leave-In Molecular Repair Hair Mask consistently for the next six hair washes to really strengthen my hair to repair the hair because sometimes when I go blonde my hair can be a little dry and sometimes I can experience breakage as well because I have fine hair. So this is something that I will use for the next six hair washes post appointment. After that I might only use this maybe two or three times per month."

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"I will use this once or twice before I go and get my hair done. And by doing that, I have noticed a really big difference with my hair. I have pretty fine hair, so I need to be careful when coloring it, when heat styling my hair, and this has made a huge difference. So, this is a non-negotiable. This always needs to be in my collection."

Dr Dray

2.66M subs · 34k devotees

✓Approved

"The K18 Leave-In Molecular Repair Hair Mask is one of my favorite bond repair products. It works by having an actual mechanism within the ingredients that helps to temporarily reapproximate damaged bonds in the hair. I put this one through the test, and this product works. It does what it says it's going to do. Not only does it work, it works well."

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"I had heard such wonderful things about K18. So, I decided to try their molecular repair hair mask. And it really just made a huge difference for me at that time. In particular, it contains a peptide that helps to reapproximate damaged bonds from heat styling, color treatments. It works not only across the hair strand, but down the length as well. So, it helps improve smoothness, shine, manageability. The way you use this kind of trips people up. You use it after you shampoo the hair, but you do not want to condition. Then, you get out of the shower, you towel dry the hair, and you just use a few pumps of this product. A little bit goes a long way. You distribute it all over the strands and let it sit on there for 4 minutes. After the 4 minutes, you can put on a leave-in conditioner or whatever styling product you want. The reason you don't want to put conditioner on before though is that it'll keep the active ingredient in the hair mask from really being able to access the strand optimally and for you to get the best results. I used it a lot in order to kind of correct that damage and make my hair a little bit more manageable."

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"This product really works. What it does is it helps to reapproximate bonds in the hair. It works along the length of the hair and along the width of the hair. And what that does is help to mend damaged hair from heat styling, dyes, chemical processing, and it really works. The way to use it is you shampoo your hair like you normally would. Then you do not want to put on conditioner. The reason you don't want to put on conditioner is because if you put conditioner on, then the mask ingredient will not be able to access your strand. So when you get out of the shower, you towel dry the hair so it's just a little damp. And then all you need is like three pumps. You don't want to use too much because it'll actually kind of weigh down your hair. Just three pumps to the entire strands. And then you leave it on for approximately 4 minutes. And then you can do whatever you want to your hair. You can put a leave-on conditioner on if you feel like you need more conditioner. But honestly, this conditions by reapproximating those bonds like that."

Dr. Aleksandra Brown

104k subs · 4k devotees

✓Approved

"For bond repair, I love the K18 Leave-In Molecular Repair Hair Mask. This is not your typical deep conditioner. It's a biomimetic hair treatment that repairs broken hair chains at a molecular level and restores the strength and elasticity. It works in just 4 minutes to help reverse the damage from bleaching, coloring, heat, or any chemical treatments. Unlike traditional bonding treatments, K18 permanently reconnects keratin chains for lasting damage repair. The key ingredient is the K18 peptide, which is a patented peptide that mimics natural hair structure to rebuild keratin proteins."

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"The K18 leave-in molecular repair hair mask is my first recommendation in the hair care category. It can be pricey and comes in a tiny package, but it lasts a very long time. This is not your typical deep conditioner. It's a biomimetic hair treatment that repairs broken keratin chains at a molecular level, therefore restoring strength and elasticity. It works in just 4 minutes to reverse that damage for any bleaching, coloring, heat, or any chemical treatments you may have done. Unlike traditional bonding treatments, it permanently reconnects those keratin chains for longer lasting damage repair. The key ingredient is the keratin peptide, which is a patented peptide that mimics natural hair structure to rebuild those keratin proteins."

No BS Beauty

89k subs · 2k devotees

✓Approved

"The K18 molecular hair mask, you just use a little bit. In the shower, wash your hair, don't apply conditioner, and then when you get out of the shower, I'll just apply a dime-size amount, rub my hands together, and then just apply it to the very ends of my hair, and it does a nice job. This is more for color-treated hair, permed hair, damaged hair. If you don't color treat your hair or perm it or do anything like that, there's I think this might for some people end up making your hair worse off. I've heard certain proteins and peptides if you use them on hair that's not damaged it can make it worse."

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"Their leave-in conditioner mask is nice. One thing I want to mention, I haven't repurchased this more than a couple times because I use such a small amount of this. The bottle is 1.7 oz, so I literally use almost a pea size, which I can't get away with doing almost pea size with almost anything, but with this one it works well. It's the K18 hair mask, it's really nice. It's expensive, but literally I've been working on this bottle for probably a year now. So it would be repurchased if I used a ton of it at a time, which I don't. It's very nice and I like to use a good clarifying shampoo before this because I feel like it soaks in more and works better. So it's just a leave-in product, so you rinse with shampoo, don't apply conditioner, and then apply this."

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"The K18 hair mask is always very expensive in Canada, it's over a hundred dollars for this mask. I got this for my hair stylist for I think 50 bucks which I thought was a lot. I mean it does last a long time because you use such a small amount, but 101 dollars for a hair mask, I mean it's a good thing it's a good product, but there's no way I could ever justify a hundred one dollars for a hair mask. I mean the ingredients in here aren't like anything. I mean sure they had to do research and development things like that, but something just in there in my gut thing makes me think there's something else going on there."

Kelly Driscoll

90k subs · 5k devotees

✓Approved

"I've been using this for a few years and just over the last year, year and a half, I've been using this almost exclusively. After washing my hair and conditioning my hair, I will use this as a leave-on treatment. I use one pump for all of this hair, work it on my ends and then through the mids. You just leave it in. It is a reparative strengthening bonding hair product and it does work very very nicely. One way to use this is to actually replace your conditioner product with this."

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"K18 kind of entered the scene a few years ago and I named it as a monthly favorite in 2022 in the spring, I was really enjoying it then. It's a similar concept to Olex. I think it really helps to strengthen my hair and helps to keep it in really good shape. I think it helps to resist some split ends and damage on my hair as well in between trims. It's really expensive, it's retailing $75. That is not what it retailed back in 2022, it was still pretty pricey, I think it was pushing maybe $60, which is still I think too much. They raised the price recently. I don't really understand why this is so freaking expensive. It is nice but it's tricky to use, unlike Olex where I can just put it in my hair."

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"I used the K18 Leave-In Molecular Repair Hair Mask right after washing my hair and before blow drying it. I slept on this hair, washed it last night dried it and slept on it, and there's still some nice volume at the roots. I like how this lasts."

Skin Obsessed Mary

33k subs · 3k devotees

✓Approved

"Another bond repair treatment I use regularly is K18. I actually discovered this before a prey and it really started my journey back to soft hair. Now, this is a bit trickier to use. It likes towel dried hair, which then has to be rinsed off. So, for me, it's only once or twice a month, but I keep buying it and I was super excited when they launched this big guy so I don't have to repurchase the smaller ones as frequently."

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"I love this and I specifically use this right after I get my hair colored. I will use this for three or four showers and it's a bond repair program. I prefer this to Olex. I stopped using Olex and I use this instead. I think it's fabulous. What I tend to do is I shampoo my hair, you do not condition it first, you shampoo and then you put this mask in and you leave it in for four minutes. I put my hair up and then I do shaving and all the other stuff on my everything shower days and then you rinse it out."

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"Another fantastic Bond repair product is the K18 Leave-In Molecular Repair Hair Mask. I've been using this even longer than the appre and I actually find that using them together it's the perfect pairing they repair Bonds in different ways. One is pre-shower and then the K18 I use during the shower and I love them both."

Gothamista

685k subs · 45k devotees

✓Approved

"I believe that for damaged hair, or hair like mine that's dry, brittle, and frizzy, leave-in treatments make a lot of difference, especially when you're using styling tools that apply a lot of heat. A very obvious favorite is K18 Leave-In Molecular Repair Hair Mask. Even though this is creamy, it has a really lightweight texture, at least for my hair. Right after washing my hair, I apply it to my wet strands, and my hair just dries a lot nicer, a lot less frizzy or frazzled. This is advanced hair repair technology that I think works really well in combination with bond technology; it also works from inside out but goes even deeper into the hair to help with repair. I even bought the mega-sized salon-only version from my hair salon. It wasn't cheap, but worth it."

Dr. Shereene Idriss

1.71M subs · 51k devotees

✓Approved

"I've been using their K18 Leave-In Molecular Repair Hair Mask because as my hair started to get a little bit fuller and thicker I wanted to limit the weight of heavy conditioners on my hair that adds weight to my hair but my hair needs a conditioner. I use this after I shower and it is formulated with SH oligopeptide 78 to help stimulate hair follicle activity and promote healthier scalps. I put it on my hair literally from here down after the shower a tiny drop goes a very long way and it's been working pretty well for me."

Dr. Sam Ellis

849k subs · 143k devotees

✓Approved

"The K18 Bond repair treatment is kind of my holy grail for many many years. I'm a huge fan of that product."

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"K18 is really kind of my go-to. It is a peptide treatment that is meant to penetrate into the hair shaft to help repair damaged bonds. Within your hair shafts you have thousands, millions of keratin protein and those keratin proteins can get damaged and they can become unstructured in a way where it makes the hair look dry and frizzy and prone to breakage. The whole point of the K18 peptide is really to get in there and repair those keratin chains as well as repair disulfide bonds, which is another type of bond in the hair that gives it integrity. If someone has dry hair, damaged hair from heat styling or color treating or sun exposure, then using something like K18 in your regimen I think could be amazing."

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"The K18 Bond repair treatment is kind of my holy grail for many many years. I'm a huge fan of that product."

Mixed Makeup

1.47M subs · 11k devotees

✓Approved

"People like Michelle Miller from K18 I don't know if you've seen that on Tik Tok I seen it"

Hyram

4.36M subs · 31k devotees

✓Approved

"That is a really good price for kerville I mean that's like what 70% markdown crazy I'm kind of Blown Away that they can have prices this low"

Dr. Vanita Rattan

1.22M subs · 10k devotees

✕Skip

"The second ingredient is denatured alcohol, so it's drying the hair. They have got conditioning agents, it has got hydrolyzed wheat which does help to repair protein, but you have to look at preventing first. You don't want to make the situation worse and then try and cover it up with other good ingredients. This formula just doesn't make any sense to me. I think what they were trying to do is almost give that quick dry feeling to the hair to make you feel like the ingredients have penetrated into the shaft, but it's a mistake."

Nipun Kapur

399k subs · 10k devotees

✓Approved

"K18 minimalist you can also do Hair Botox"

HotandFlashy

1.23M subs · 69k devotees

✕Skip

"I did look at the ingredients before I used it and I wasn't thrilled with the ingredients but I liked how my hair came out at first when I first styled it but the way it frizzed up I was like absolutely not. Then I was like well no wonder with these ingredients like this has very high SD alcohol so that is going to dry out my hair and sure enough it did."

Leave-In Molecular Repair Hair Mask.

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