Harklinikken is a hair care brand founded in Denmark. The brand describes their hair products as “high-quality, non-toxic and efficacious,” and they sell everything from hair growth serums to shampoo.

But do Harklinikken products contain research-backed ingredients for hair health and appearance? Does the brand use any questionable additives? Should you be sharing your health data with a shampoo brand? And how does Harklinikken compare to other luxury hair care brands like Prose and Olaplex?

In this article we’ll answer all of these questions and more, as we analyze the ingredients in two of the brand’s most popular products ( Balancing Shampoo and Hair Gain Extract) to give our take on whether or not they’re likely to be effective, and whether or not they're healthy. 

We’ll also compare the potential effectiveness and healthiness of Harklinikken to other popular luxury hair care brands, and share our concerns with the company's hair health quiz.

Balancing Shampoo Ingredient Analysis

The ingredients in Harklinikken’s Balancing Shampoo are shown above.

Lauric acid is the only ingredient in this formulation we can find research backing for in regard to hair quality.

It’s derived from coconut oil, and may be able to protect hair proteins from damage according to a medical review published in the Journal of Cosmetic Science.

Potassium sorbate is a preservative shown to be toxic to human cells in a 2010 clinical trial.

This was an in vitro (test tube) study, so it doesn’t necessarily mean the same results apply when used on hair, but it's worth noting in our opinion.

Overall, we’re quite underwhelmed with this formulation, especially at its price point of $44.

Most shampoo products we review on Illuminate Health like Better Not Younger contain many effective botanical ingredients, even if we don’t end up recommending the product for health-related reasons.

We consider Harklinikken Balancing Shampoo somewhat likely to improve hair quality due to the inclusion of lauric acid, but we don't recommend it due to the use of potassium sorbate.

Hair Gain Extract Review

Harklinikken’s Hair Gain Extract is even more expensive than their shampoo, currently costing $88 per bottle.

It’s custom-formulated but no ingredient list is shown even after completing the questionnaire (we completed it with sample responses).

We strongly urge consumers to avoid cosmetic products without an ingredient label, as it’s a safety issue. Without knowing exactly what ingredients are in the product, there’s no way to assure its safety or efficacy.

There were also some strangely personal health questions in the Hair Gain Extract questionnaire, including whether or not a user is pregnant or has given birth in the past six months.

We have no idea how or why that would impact a hair growth formulation, nor does Harklinikken share any clinical research suggesting their custom formulations are effective.

As shown above, the brand also asks how often users work out. Again, how does this affect ingredients in a hair growth product? 

We recommend that consumers be wary of giving sensitive health information to cosmetics brands for no clear benefit.

As we discussed in our review of another health brand that collects user data called Reverse Health, your health data is at risk of being hacked when it’s stored with a company.

We have not come across any convincing medical evidence that “personalized” hair care products are more effective than standard hair care products. We consider this more of a marketing strategy than a strategy founded on good science.

Does Harklinikken Cause Side Effects?

Harklniikken does not appear to have been studied in any clinical trials, so it’s challenging to say for certain whether or not the brand’s products are likely to cause side effects.

However, we can make an educated guess based on the ingredients used.

We do not consider Harklinikken likely to cause side effects in healthy individuals. Most of the ingredients used by the brand are safe, well-studied and non-toxic.

There are a few potential irritants worth noting. 

The preservative potassium sorbate that we highlighted in the Ingredient Analysis section was described as a potential irritant which is “underestimated” according to a medical review published in the Contact Dermatitis journal.

Cocamidopropyl betaine is a synthetic detergent that won “Allergen of the Year” due to its clinically proven allergenic effects, as we referenced in our review of another cosmetic product containing this ingredient called Native Body Wash.

This information suggests that Harklinikken products may cause allergic reactions in individuals with sensitive skin.

How to Properly Apply Harklinikken

Harklinikken has a YouTube video that’s only two minutes long, which shows how to properly apply their hair loss treatment:

Harklinikken vs. the Competition

Here's how Harklinikken stacks up against other luxury hair care brands in our opinion:

Olaplex

Contains more research-backed active ingredients, but also contains more questionable inactive ingredients (like preservative chlorphenesin which is clinically shown to be toxic to human cells).

Winner: Tie — Olaplex is better from an efficacy perspective and Harklinikken is better from a safety perspective

Humby Organics

Contains fragrance, but also contains more research-backed active ingredients to support hair health. Also uses plastic-free packaging, as we documented in our Humby Organics review article, which is a plus.

Winner: Humby Organics

Prose

This personalized hair care brand uses a wide range of exotic botanical ingredients with research backing, and offers fragrance-free versions of most of their products.

Winner: Prose

Our Clean Hair Growth Picks

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%.

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."

MBG Omega-3 Potency+ is our top hair thickness pick.

Supplementation with omega-3 fats and antioxidants is clinically shown to improve hair density, and MBG's supplement contains both.

All of the products recommended in this section are entirely free of ingredients we consider to be unhealthy.

Harklinikken Pros and Cons

Here are the pros and cons of Harklinikken in our opinion:

Pros:

• Lauric acid may protect hair from damage
• Great branding & packaging
• Unlikely to cause side effects

Cons:

• Shampoo contains potassium sorbate
• Shampoo has unimpressive formulation for the price
• Health quiz asks unnecessary personal questions
• Expensive
• Challenging to find unsponsored customer reviews on YouTube or TikTok
• Doesn't appear clinically tested

Conclusion

We are unimpressed with Harklinikken as a brand, especially given their prices.

We do not currently recommend the brand’s shampoo due to the inclusion of a preservative ingredient, but also because we only consider one of its active ingredients likely to improve hair quality.

We do not recommend Harklinikken Hair Gain Extract because the brand doesn’t even publish the ingredients after you complete their questionnaire.

There are no particularly harmful or dangerous ingredients in Harklinikken hair products (those with an ingredient label), so we do not believe the brand will cause side effects in healthy individuals.

There are a few potential allergens that could cause side effects in individuals with sensitive skin.

We consider Harklinikken to be equivalent to luxury hair care brand Olaplex from a formulation perspective, but inferior to luxury hair care brands Humby Organics and Prose.