K18 is a hair care brand that positions itself as more scientific and research-based than the average consumer hair products brand. The company describes itself as “biomimetic hairscience” that provides “molecular repair.”
But are these just fancy marketing terms or is K18 actually based on better science than most hair care brands? Do K18 products contain ingredients proven to repair and improve hair quality in clinical trials? Do they contain any questionable additive ingredients? And how do real users rate and describe the effects of K18?
In this article we’ll answer all of these questions and more as we analyze the ingredients in two of K18’s most popular products: Molecular Repair Hair Mask and PEPTIDE PREP Detox Shampoo. We’ll give our take on whether each product is likely to improve hair quality or if it’s a waste of money.
We’ll also provide a cost comparison featuring which retailer sells K18 for the best price, and feature real, unsponsored K18 reviews including before-and-after images.
K18 Hair Mask Ingredient Analysis
The ingredients in K18 Molecular Repair Hair Mask are shown above.
Polysorbate 20,sh-Oligopeptide-78 (trademarked as “K18PEPTIDE”) is the key active ingredient, and the brand claims that this ingredient “works on the molecular level.” However, we cannot find any evidence in clinical trials proving this ingredient to be effective, nor does K18 cite any on their product page.
We can’t even identify any clinical trials testing this ingredient or proving its safety.
Hydrolyzed wheat starch is another strange active ingredient. We found clinical studies proving that hydrolyzed wheat protein is an effective natural hair conditioner, but we can’t find any proof of efficacy or safety of hydrolyzed wheat starch.
There are no active ingredients in this formulation that we can find clinical backing for, which is surprising especially given the price point ($75). In the majority of Illuminate Health hair product reviews, we’re able to at least source clinical backing for one of the active ingredients.
There are a number of additive ingredients in K18 Hair Mask that we consider questionable from a health perspective.
Fragrance is an ingredient category which was analyzed in a medical review published in the Air Quality, Atmosphere & Health journal. After reviewing clinical trial data, the researchers concluded that fragranced consumer products can "impose serious risks to human health."
Phenoxyethanol is a synthetic preservative shown to be toxic to human cells in a 2020 clinical trial.
Behentrimonium chloride and benzyl alcohol are additional preservative ingredients, and geraniol, linalool and hexyl cinnamal are additional fragrance ingredients.
Overall we do not recommend this hair mask due to the additive ingredients and lack of demonstrated efficacy.
But how do real users rate and describe K18 products? We’ll review in the next section.
Real, Unsponsored K18 User Reviews
A YouTube creator named Daniela Anguiera reviewed K18 in a video with over 100,000 views and shared before and after images:
Another YouTube creator named “Manes by Mell” reviewed K18 and her review included a product demonstration, her thoughts after using the products for six months, and a comparison to another popular hair repair brand called Olaplex:
K18 Shampoo Review
The ingredients in K18 PEPTIDE PREP detox shampoo are shown above.
Some of the active ingredients are similar, but there are some ingredients in this formulation we consider likely to be effective.
Charcoal powder was found to be effective in treating some skin disorders in a medical review published all the way back in 1947, which suggests that this ingredient may improve scalp health and reduce the risk of conditions like dandruff.
Panthenol and glycerin also work synergistically to support a healthy scalp, as we referenced in our review of another hair brand called Plantur 39.
Salicylic acid is a naturally-derived exfoliator, as shown in a clinical trial published in the Cutis journal.
We can’t locate any ingredients shown to “detox” the scalp, nor have we come across any convincing clinical evidence that the scalp needs “detoxing” beyond regular washing and drying.
Like the hair mask, this product contains a number of questionable additive ingredients.
Benzyl salicylate is a preservative and scent ingredient that was categorized as a “hazard class 2” in a Japanese regulatory screening due to its toxic effects in animal studies.
Fragrance and limonene (a fragrance ingredient) are also included in this formulation.
We do not recommend this product due to the additive ingredients, but we consider it to be better-formulated than K18’s hair mask.
But what retailer sells these products for the best price? We’ll review in the next section.
Which Retailer Sells K18 for the Best Price?
K18 is sold at a variety of online retailers. Here’s a price breakdown for the two products reviewed in this article:
K18 Hair Mask
Walmart: $75 (free shipping but third-party seller)
Brand website: $75 (free shipping – link)
Amazon: $75 (free shipping – link)
K18 Detox Shampoo
Walmart: $41.93 (third-party seller)
Brand website: $38 (plus shipping fees if single order)
Amazon: $38 (free shipping depending on plan – link to official Amazon listing)
K18 Hair Mask is the same price on all platforms. The Detox Shampoo is 5-10% cheaper on Amazon than on the brand’s website for single orders, because K18 currently charges shipping fees for orders under $50.
We recommend avoiding third-party sellers and purchasing directly from the manufacturer to reduce the risk of fake or counterfeit products.
K18 vs. OIaplex
Olaplex is another hair care brand centered on technology and hair repair, so consumers are often curious about which is a better option.
We reviewed Olaplex extensively in our Olaplex ingredients article, and we consider Olaplex to be a slightly better option than K18 although we don’t recommend either brand.
As documented in our ingredient analyses, both Olaplex No. 3 and Olaplex No. 4 contain at least one research-backed ingredient that’s clinically shown to either improve hair breakage resistance or support hair regrowth.
We were unable to identify such ingredients in K18’s shampoo, and only were able to identify scalp-supportive active ingredients.
Olaplex contains a number of questionable additives like fragrance and synthetic preservatives which is why we recommend avoiding the brand.
Real Customers Review K18
Amazon is a better resource for honest customer reviews than a brand’s website in our opinion.
The brand’s most-reviewed product on Amazon is their hair mask, which currently has over 2,700 reviews and an average review rating of 4.4 out of 5 stars.
The top positive review from a verified purchaser comes from a user named “Silvia” who claims that with a bit of customization it works well with her hair care routine:
“After 4 minutes i add the rest of my hair products and my hair feels so soft. Go based on how it feels once you apply it, I followed the recommended 4 pumps and felt like my hair didnt need as much so I went down to 2 with the concentration of the top section since it has the most damage.”
The top negative review from a verified purchaser is written by a user named “Jenny Baber” who claims it’s ineffective:
“The 'bonding' claim is a gimmick! Feeling my hair right now after 6 consecutive uses. Still breakage. PLEASE save your money. This is just...snake oil...plain and simple. Just because science is claimed, doesn't mean the science works…”
Our Clean Hair Care Picks
Acure Vivacious Volume Shampoo is our top shampoo pick, and only costs $7.49 at the time of updating this article.
This shampoo is formulated with effective and non-toxic plant-based compounds like aloe vera juice and argan oil. It also contains rosemary leaf oil which was shown in a clinical trial published in the Phytotherapy Research journal to promote hair growth.
Happy Head Topical is our top hair growth solution.
This formulation uses FDA-approved hair loss ingredients like minoxidil which is clinically shown to increase hair count by 11%.
The brand also publishes the percentage concentration of each active ingredient, which is a sign of quality and transparency.
Pros and Cons of K18
Here are the pros and cons of K18 in our opinion:
- Great branding
- Shampoo contains some research-backed ingredients
- Mostly favorable customer reviews
- Contains fragrance
- Contains synthetic preservatives
- We can’t identify any hair restoration ingredients
- Unimpressive formulations for the price