I Tried This Celeb-Hyped, Molecular Repair Hair Treatment for 2 Months on My Damaged Stands—The Results Are Jaw-Dropping

Photo: Getty Images/ Cavan Images
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As a mid-30-something who’s been coloring her hair blonde since middle school, you better believe my strands have seen their fair share of damage. Spending three hours in a salon chair every 2-3 months as my stylist sandwiches my hair in between tin foils to essentially fry it under a heat lamp has resulted in more split ends than I know what to do with. Luckily, my job as a beauty journalist has afforded me the chance to try just about every hair product under the sun, most of which don’t stand a chance against repairing my dry and brittle locks—and that includes the celeb-loved K18 haircare brand.

I had tried pretty much every hair product under the sun before someone recommended K18, the brand that’s beloved by celebrities by the likes of Hailey Bieber, Rihanna and Selena Gomez. I’m not one to fall for a product just because a Hollywood A-lister swears by it, but what caught my attention is the its promise to actually repair damage caused by chemical processing, hair highlighting, sun exposure, heat styling, you name it.

What is K-18, and what makes it special?

Unlike most haircare products that work from the outside in to hydrate strands and make them look healthier, K18's line of products, including its now-famed K18 Leave-In Molecular Repair Hair Mask ($75), is patented for clinically improving hair on a molecular level, repairing polypeptide chains that have been broken over time. It essentially mimics the natural biochemical processes involved in hair’s natural growth structure and development, explains Cassondra Kaeding, Celebrity Stylist and K18 Ambassador.

Just before I signed off “yes” to begin my K18 treatment, which is essentially a step-by-step process involving their products, I was quite disappointed to learn I had to give up one hair care product I held dear to my heart: conditioner. If you’re a dry-haired girl like me, you live for conditioner. In fact, the only way I can brush my hair is by using an alarming amount of conditioner. But, as it turns out, skipping conditioner when using K-18 is vital to allowing it to work properly. In fact, most conditioners out there contain certain ingredients like silicone that coat the hair and prevent the K18 from actually being able to penetrate and repair the broken bonds.

My honest review of K-18

That information was convincing and compelling enough for me to give it a shot. I started out with a few of their basic products, including their K18 Peptide Prep pH Maintenance Shampoo ($32) which was useful for someone like me who tends to use a ton of products in their hair. This product works deep within the cortex of the hair to heal the hair from the inside out, explains Kaeding. “If there is buildup on the surface of the hair, the peptide will not be able to penetrate and the product will just sit on the surface of the hair,” she says. She recommends a clarifying shampoo like the K18 Peptide Prep Detox Clarifying Shampoo ($34) to anyone who frequently uses dry shampoos, heavy oils or silicones so that the K-18 treatment can work to its optimal abilities.

In the shower, I’d apply the clarifying shampoo and then towel dry my hair—no conditioner—and then apply the K18 Mask directly after the shower. I left the mask on for four minutes, as instructed, to ensure that it was fully absorbed. I could not believe that I actually had no trouble brushing through my hair after that four minutes was up. No conditioner, yet here I was brushing through my usually-tangly strands without trouble.

I used the product for a total of two months and switched between the Peptide Prep Detox Clarifying Shampoo and the Peptide Prep Shampoo, which are both color-safe and pH-optimized, and designed for daily use. The latter is also formulated with amino acids, which help strengthen the hair shaft.


I was so impressed with the K-18 hair care line and noticed improved results almost immediately. My hair was more brushable, it had more shine, it looked healthier and it moved more freely. I noticed after about three uses, my hair started completely changing—like the entire biology of my hair shifted to the point where I felt like I had reversed several year’s worth of damage.

Photo: Jenn Sinrich

I will say that, in order for the K18 mask to work, you really have to be diligent about using it. I went on a short vacation to Florida and forgot to pack the molecular repair mask and noticed my hair felt more coarse and less healthy. Once I returned home and started using it again, I again saw the improved health.

My hair by the end of June:

k 18 final
Photo: Jenn Sinrich

Luckily, a little bit goes a long way—which is good, because the line is not cheap. The mini version, which is just .5 ounces costs $29 and the bigger one is $75 for just 1.7 ounces. At first, this seemed like a total rip-off, but I will say that you really don’t need much. In fact, you don’t want to overdo it and use more product than you need. “Since K18 works deep within the cortex of the hair, whatever is not absorbed into this area will just sit on the surface of the hair,” explains Kaeding. “This could cause the hair to feel a little weighed down.” She recommends using just 1-2 pumps for short hair and 2-3 for longer hair.

Overall, I would recommend K18 to anyone with super damaged hair—I definitely don’t think this treatment is necessary for anyone with basic dry hair who is in need of a little pick-me-up. There are plenty of conditioners and masks out there that can do the job of hydrating dry hair. If, however, you’re looking for a product to actually repair the broken molecules that are causing this breakage and dryness, turn to K18.

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