Benzyl alcohol is an aromatic alcohol used at 0.5% in the formulas and acts as a preservative. It does not contain ethanol and therefore is used in products that are marketed as alcohol-free. I’m pretty skeptical when it comes to viral products—it’s practically my job to wade through what actually works and what’s B.S., but trust me when I say K18 is very much worth the hype. Though the hair mask has recently been gaining steam on TikTok, it’s actually been making noise in the beauty community since it launched in 2020; it’s been endorsed by some of the best colorists and stylists in the biz—which is why it’s crazy that it’s taken me so long to try it.

I always worry that my hair will feel greasy after using moisturizing products/treatments, but this dries naturally and doesn’t leave any residue. I would say that maybe my hair is too damaged for this to repair, as I did notice it felt softer, but there definitely are still a lot of split ends in there.

Insights on the mechanical behavior of keratin fibrils

By reconnecting these polypeptide chains, the mask strengthens along the length and width of the hair, offering a full 360 approach. Isopropyl alcohol is at a very low level (about 0.5%) in the K18 Mask formula. It is part of an ingredient blend, but it is not directly added to the formulas. It acts as a solvent by making the conditioning agents able to blend into the formulations. Although K18Hair is free of sulfates, parabens, phthalates, silicones, artificial colors, sodium chloride, formaldehydes, is vegan, and cruelty-free, we recommend that clients always consult their doctors as they will have individualized care plans. We are happy to provide MSDS sheet.

The K18 Leave-In Molecular Repair Hair Mask is an award-winning haircare product—it’s been compared to (and is purportedly more effective than) the industry standard, Olaplex’s No. 8 hair mask. K18’s hair mask has even been hailed as a replacement for conditioner. Does it actually work? Four W editors put it to the test, and gave their honest opinions. 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? Detangling and conditioning benefits are just an added bonus. As long as you leave it on for 4 minutes, you can add a leave in conditioner, if desired. If heat styling, it is important to use a heat protectant after the 4-minute processing time. Why do you skip conditioner?K18 is designed to be used consecutively for 6 washes and then every 3-4 washes to maintain your healthiest hair possible.

K18Peptide™ is not able to regenerate bonds in the presence of too much water inside the cortex. However, the hair needs to be slightly damp to help with penetration of the product into the hair. 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. Cetearyl alcohol is a fatty alcohol with a wax-like consistency. It is often used in hair care conditioning formulas because of its smoothing and softening qualities. It does not contain ethanol and therefore is used in products that are marketed as alcohol-free. K18 is more effective when left in. The formula is lightweight and works on the inside of the hair, so the hair is left feeling clean and light, even without rinsing it out. Can I use styling products with K18?

K18 is most effective on clean, towel dried hair. Conditioner formulas use silicones and conditioning agents that form heavy coatings on hair that prevent K18 Peptide from penetrating to the broken disulfide bonds within the cortex. You may use conditioner after K18 has processed for 4 minutes if needed, not before. Water (Aqua) (Eau), Sodium C14-16 Olefin Sulfonate, Cocamidopropyl Hydroxysultaine, Salicylic Acid, Charcoal Powder, sh-Oligopeptide-78, Panthenol, Glycerin, Sodium Phytate, GuarHydroxypropyltrimonium Chloride, Caprylyl Glycol, Caprylhydroxamic Acid, Citric Acid, Potassium Hydroxide, Sodium Hydroxide, Fragrance (Parfum), Benzyl Salicylate, Limonene. My hair has been dehydrated with the sun and heat damage of summer, so this was perfect timing to try K18. It was not time-consuming. I used it every time I washed my hair for two weeks, and used about 3-4 pumps each time because of my long hair. I thought using it every time I washed my hair might be overkill, but for how coarse my hair is, it works perfectly . K18’s primary goal is to restore your hairs strength and elasticity by repairing the keratin chains damaged from bleaching, coloring and thermal heat.

No, the formula is lightweight and works from within the hair so hair is left feeling clean and light. K18 is not organic because only natural ingredients can be certified organic. K18 uses both natural and synthetic ingredients because we prioritize cleanliness and safety. We highly encourage it. Our hair is not only damaged by color, but from heat, sun, products, water and environmental aggressors. K18 restores your hairs health and reverses any damage, everyone can benefit from K18. Krupa Koestline, a cosmetic biochemist who has worked with brands that strive to create naturally derived products. She is based in Orlando, Florida. No, K18’s strengthening and smoothing results are clinically proven to remain in hair, even after repeated shampoos.

My honest review of K-18

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. 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. My daily haircare routine consists of a cold shower and letting my hair air dry. That’s it! I’m a big believer in air drying so that your hair curls naturally. I’ll use Moroccan oil shampoo and conditioner three times a week, but I can’t shampoo any more than that, otherwise my hair will become super dry. I’m really a less-is-more kind of hair guy, so it’s safe to say I’ve never done anything like the K18 treatment before. I was hesitant about not using conditioner and using K18 as a leave-in conditioner instead, but it made my hair feel significantly softer. I like how it is not heavy or does not change the weight of my hair. I still used my hair oil to control frizz, but my hair is naturally on the frizzier side. I saw real results in a short amount of time. I loved it and will continue using it! This size of the bottle is also perfect for traveling this summer. Jenna Wojciechowski, Fashion Market Editor