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 based on advanced science? Do K18 hair products contain research-backed ingredients? Does the brand use any questionable additives? 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 or not these products are likely to improve hair quality and hair appearance, and whether or not they're healthy.
We’ll also provide a cost comparison documenting which retailer sells K18 for the best price, and feature real K18 customer reviews, including before-and-after images.
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 can't find any evidence in clinical trials proving this ingredient to be effective, nor does K18 currently cite any on their product page.
Hydrolyzed wheat protein is clinically shown to be an effective natural hair conditioner.
There are a number of inactive ingredients in K18 Hair Mask that we consider to be 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 consider K18 Hair Mask to be potentially effective for supporting hair quality due to the inclusion of hydrolyzed wheat protein, but we don't currently recommend this product due to the many inactive ingredients discussed above that we consider to be unhealthy.
Real People Try K18
A YouTube creator named Daniela Anguiera reviewed K18 in a video with over 100,000 views that includes before-and-after images:
A YouTube creator named “Manes by Mell” shared her experience after testing K18 for six months, and compared the brand to Olaplex:
Shampoo Ingredient Analysis
The ingredients in K18 PEPTIDE PREP detox shampoo are shown above.
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 may 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.
Overall, we consider K18 PEPTIDE PREP Shampoo to be somewhat likely to improve hair quality and appearance, and we consider it to be better-formulated than the brand's hair mask, because we're able to identify multiple research-backed active ingredients in this product.
We don't currently recommend this product due to the inactive ingredients discussed above.
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.
Customers Rate K18
Amazon is a better resource for honest customer reviews than a brand’s website in our opinion.
K18 Hair Mask currently has over 19,000 reviews on Amazon, and an average review rating of 4.3 out of 5 stars.
A top positive review from a verified purchaser comes from a user named “Silvia” who gave the product a 5/5 rating:
“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.”
A top negative review from a verified purchaser is written by a user named “Jenny Baber” who gave the product a 1/5 rating:
“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.
It contains argan oil which is clinically shown to help protect hair from damage.
Happy Head Topical is our top premium hair growth solution.
This formulation uses FDA-approved hair loss ingredients like minoxidil which is clinically shown to increase hair count by 11%.
Ritual HyaCera is our top hair growth supplement.
This supplement contains wheat oil extract, and a 2024 clinical trial reported that a wheat lipid complex had "a reducing effect on hair shedding and a stimulating effect on hair reappearance and growth."
All of the products recommended in this section are entirely free of ingredients we consider to be unhealthy.
Where to Get the Best Price
K18 is sold at a variety of online retailers.
Here’s a price breakdown for a one-time purchase of the two products reviewed in this article, at the time of updating this article:
K18 Hair Mask
Walmart: $75 (free shipping, third-party seller)
Brand website: $75 (free shipping, link)
Amazon: $75 (free shipping – link to official Amazon listing)
K18 Detox Shampoo
Walmart: $41.93 (third-party seller)
Brand website: $38 (plus shipping, link)
Amazon: $38 (free shipping, link to official Amazon listing)
Amazon currently has the best prices when factoring in shipping fees.
K18 Pros and Cons
Here are the pros and cons of K18 in our opinion:
Pros:
- Great branding
- Shampoo contains some research-backed ingredients
- Hair mask may support scalp health
- Positive Amazon reviews
Cons:
- Contains fragrance
- Contains synthetic preservatives
- Expensive
- We can’t identify any hair restoration ingredients
- Unimpressive formulations for the price
