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 is K18 really based on advanced science? Does the brand use research-backed active ingredients? Does it use any unhealthy ingredients? And is K18 better or worse than popular hair care brands like Olaplex?
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) to give our take on whether or not they're effectively formulated.
We'll also compare K18 to other popular hair care brands like Olaplex and Briogeo, in terms of formulation quality, to pick our winners (and losers).
Key takeaways:
- We can't find any evidence that K18PEPTIDE is effective
- Both products analyzed contain ingredients we consider unhealthy
- We do not currently recommend K18
Hair Mask Ingredient Analysis
The ingredients in K18 Molecular Repair Hair Mask are shown below:
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 highlighted above that we consider to be unhealthy.
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.
Shampoo Ingredient Analysis
The ingredients in K18 PEPTIDE PREP detox shampoo are shown below:
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 highlighted above.
K18 vs. Popular Hair Care Brands
Here's how K18 compares to other popular hair care brands in terms of formulation quality, in our opinion:
Briogeo
This brand utilizes many research-backed active ingredients, including peppermint oil, which is clinically shown to support hair growth.
We analyzed two formulations from this brand, and they only contained one unhealthy ingredient combined, making Briogeo a healthier choice overall than K18.
Winner: Briogeo
Hairitage
Hairitage is a celebrity hair care brand that's similar to K18 in terms of formulation quality.
The brand contains research-backed active ingredients, but fewer inactive ingredients we consider unhealthy, so we give Hairitage the advantage from a health perspective.
Winner: Hairitage
Viori Shampoo
This is a shampoo bar, which is a healthier option (and better for the environment) than plastic-bottled shampoo like K18.
Viori contains fragrance, but no other unhealthy additives, so we consider this brand to be healthier than K18.
Winner: Viori Shampoo
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.
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."
Both of the products recommended in this section are free of ingredients we consider to be unhealthy.
K18 Pros and Cons
Pros:
- Great branding
- Shampoo contains some research-backed ingredients
- Hair mask may support scalp health
Cons:
- Contains fragrance
- Contains synthetic preservatives
- We can’t identify any hair restoration ingredients
- Less healthy than competitors
