What Is K18, and What Makes It Different From Other Hair Treatments?

TikTok has been buzzing over the #K18HairFlip, a hashtag created by hair-care brand K18, which has accumulated 10.6 billion views on the platform as of this publication. Influencers like Mikayla Nogueira (11.3 million followers) and Brad Mondo (8.7 million followers) have partnered up with the brand, and there is a treasure trove of videos reviewing its insanely popular Leave-In Molecular Repair Hair Mask. It's been compared to Olaplex, featured in stunning before and afters, and been given the 60-second review treatment. Yeah, people love it — but at $75, it's significantly more expensive than its competition.

So, what separates K18 from traditional bond-building products? Is it a mask or a leave-in conditioner? Which hair types can use it, and how do you use it? With the help of some cosmetic chemists and several hairstylists, here's everything you need to know about K18 before you reach for it.

• Suveen Sahib, cofounder of K18 and Aquis. He is based in San Francisco.
• Krupa Koestline, a cosmetic biochemist who has worked with brands that strive to create naturally derived products. She is based in Orlando, Florida.
• Javon Ford, a cosmetic chemist who makes his own skin-care products. On Tiktok, he shares his thoughts on popular beauty products to his 152,000-strong following. He is based in Los Angeles.
• Natalie Ruzgis, a hairstylist at the Thrive Hair Collective in Chicago.
• Daniel Kim, a hairstylist who works in Los Angeles, as well as Austin and Dallas, Texas.
• Jon Reyman, a bicoastal hairstylist and cofounder of Spoke & Weal Salon, which has locations in Boston, Chicago, New York City, Nashville, Palo Alto, Los Angeles, and San Francisco.

What Is K18?

Think of your hair as a ladder that is made up of bonds. Disulfide bonds are the horizontal rungs of the ladder. There are also polypeptide chains that are the sides of the ladder, connecting the rungs vertically. When our hair undergoes any type of damage, those horizontal disulfide bonds can be broken — hence why bond builders have become more popular before, during, and after chemical treatments, explains K18 cofounder and CEO Suveen Sahib of the research he and his team did to create the product. Most bond builders make the outer structure of the hair — the hair cuticle — look smooth, glossy, and less damaged. As for the vertical polypeptide chains, though, they cannot be patched or "glued" together, which is where K18 comes in.

K18 works at a deeper level to molecularly change and repair the polypeptide chains that have been broken, as well as reconnecting the disulfide bonds. "K18 replicates the entire structure of these polypeptide chains," says Sahib. "When they break, [K18] goes in there and reconnects them as if they weren't damaged, bringing the chains back to the state that they were before they got chemically damaged. It mimics the structure."

This is why the brand refers to itself as "biomimetic hair care" – biomimetic meaning "mimicking biochemical processes," as it works to restore the hair's original structure. We sent Orlando-based cosmetic chemist Krupa Koestline a list of K18's ingredients, and she notes the "usual suspects" when it comes to ingredients found in hair care, such as quaternary ammonium salts, fatty acid alcohols, amino acids, and polymers. "I also see alcohol listed as a second ingredient on all of these, which can be drying to hair if it is not formulated properly," she points out.

Javon Ford, a cosmetic chemist based in Los Angeles, mentions that the inclusion of ingredients like dicaprylyl ether (which is emollient) and fatty alcohols balance the hair so it isn't drying or stripping to any hair type. Ford was also interested to see dicaprylyl ether included on the ingredient list. "It's this superlight, silky emollient, and silicone alternative that's easily absorbed into the hair shaft without leaving a greasy feel. It definitely plays a role in how the product feels and performs," he explains. "Ethers aren't used enough in hair care." He says that ethers are lighter and generally have a lower molecular weight, which allows them to be absorbed by the hair cuticle versus sitting on top of it.

Both Ford and Koestline could not confirm how deep K18 actually penetrates based on the ingredient list alone, but Koestline states that both this and Olaplex's repair disulfide bonds; Ford mentions K18's bond builder is based on peptides while Olapex's is based on a modified version of maleic acid. "Maleic acid is an organic acid (like alpha and beta hydroxy acids) that's been demonstrated to strengthen hair bonds and prevent future damage," says Ford. "I mention it because Olaplex's patents not only protect its maleic acid-derived bond builder (bis-aminopropyl diglycol dimaleate) but also prevent any copycat bond builders from using maleic acid."

Ford further explains that K18's bond builder is based on short chains of amino acids (peptides) that are already present in the hair, so it's a different mechanism. "No studies have been done comparing the two, so the best approach is to try both out and see if your hair likes it and whether or not you notice a difference versus using a nice hair mask," he notes.

The Right Way to Use It

One common gripe from professionals and consumers (and also this writer) is that hair-care treatments tend to take up a lot of time and require a fresh shampoo to start. Then, you apply your treatment and wait 10 to 20 minutes for it to take effect before rinsing the product out. Or, if it's something you use after the shower, your entire head has to be saturated with product for it to take effect. Add on some extra time if you've got to detangle first.

K18's hair mask is similar to a leave-in conditioner in how it's used. You shampoo your hair, forgo traditional conditioner, then use a pump (or more, depending on hair length and density) of K18 on towel-dried hair, prior to styling. The only crucial instruction is to evenly distribute the product and allow it to work four minutes on the hair before styling. There's no do-si-do with hair washing.

"(The client's) hair is noticeably softer and has shine for days," says Chicago-based hairstylist Natalie Ruzgis. "The best part is giving clients homework — nine out of 10 times they come back with healthier, better looking and feeling hair than before. They also want to purchase more. The proof is when clients want to use it in their regular routines."

The professional option — which includes a mist and the leave-in mask — may not be as intuitive as other standalone treatments, though. "It's not confusing, but you do need to memorize when to use what product and how much you leave the product in before rinsing," says Austin-based hairstylist Daniel Kim. "It is a less-straightforward treatment system than others." Kim also says he would recommend this product, as his clients' hair does feel softer and more conditioned after use, but he wasn't positive if the patented ingredients in K18 were truly repairing the hair.

Who Should Use K18?

K18 claims to be for every type of hair that has been damaged due to chemical treatments, including curly and coily hair. "What we found is if [the client has] curly or coily hair that has been catastrophically damaged with heat or chemical services, it'll start to revert back (to the curl)," explains Jon Reyman, bicoastal hairstylist, K18 ambassador, and co-owner of Spoke & Weal Salons. 

However, there are a few things to note about the formula. "It does have a good amount of ethanol, which curly hair types tend to avoid," says Ford, but as we mentioned earlier, it's balanced out with emollient ingredients, keeping the consistency lightweight but moisturizing. For curly or coily hair, Ford suggests using an additional leave-in conditioner after K18 to make sure the hair is properly moisturized.

Also, there is hydrolyzed wheat protein in the formula, which has a low percentage of gluten. "This may not pose an issue, but it's something anyone with [a wheat or gluten] sensitivity should know so they can decide whether they want to try it out themselves," says Ford.

When you consider everything, it doesn't appear that K18 is really a competitor to Olaplex  — it's more like something that offers another level of hair restoration. "Olaplex does some pretty remarkable things," says Reyman. "And they paved the way for this conversation. However, they're limited. I think of Olaplex as a BlackBerry. K18 is the new iPhone. It just does more — better, faster, easier."

More explainers for you to check out:

• Gray Hair Guide: Everything You Need to Know About Going Gray
• How to Give Yourself a Cryotherapy Facial at Home
• How to Shave Your Head Into a Cool Buzz Cut at Home

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