Reparex (For Grey Hair): Does It Really Reverse Greying? | Scientific Analysis

Article Summary

Reparex’s Against Grey Hair claims to “restore hair color naturally from the inside out”. During our company investigation, we found discrepancies between Reparex’s marketing claims and the mechanisms governing the graying process. We also found duplicative before-after photosets serving as customer testimonials. Are these marketing department errors, or are they indications that the product doesn’t work? In this review, we assess the science behind Reparax, offer recommendations to the company, and reveal potential candidates for their “For Grey Hair” product line.

Full Article

Reparex Against Grey Hair is a product that claims to “restore hair color naturally from the inside out, unlike hair dyes”.^[1]Reparex, (no date), Reparex Against Grey Hair. Available at: https://reparexshop.com/usa/reparex-against-grey-hair (Accessed: 30 January 2023 Reparex is owned by a company called BOOS Labs – established in 1991 – which makes many different cosmetic products.

Reparex Against Grey Hair doesn’t have any clinical efficacy and safety data associated with it and there are some inconsistencies in the information provided on their website (more on that below). However, let’s take a look at what mechanistic data might be available for this product (if any) and determine if it is a product that is worth your time and money.

Key Takeaways

• Branding. Reparex markets Against Gray Hair products as topically applied alternatives to commercially available hair dyes. Their branding is marketed towards both men and women. 
• What makes it unique? Reparex attempts to differentiate  itself from other hair colorant products by claiming that its product uses a unique mechanism. They state that  “Reparex removes Oxygen from oxidized colorless melanin using the enzyme g-reductase which binds with silver nitrate. This results in the restoration of melanin’s natural color”.^[2]Reparex, (no date), How does it work? Available at: https://reparexshop.com/usa/reparex-against-grey-hair (Accessed: 30 January 2023
• Clinical Support. Currently, no clinical data is available to show us the efficacy and safety of this product.
• Concerns.
  •  The major concern for this product is that there is no mechanistic, efficacy, or safety data (and the explanation they do provide doesn’t make a lot of sense). Basically, this means that we don’t know if this product actually works or whether it’s safe to use for any length of time. 
  • The websites and documents associated with this product include conflicting and sometimes incorrect information. This makes it confusing to navigate or really understand how the product works.
  • The before-and-after photos shown on the website appear to show the same photo for both the before and after shots. Also, in some  photos, it is impossible to actually tell if the after photo is of the same person as the before photo (examples below).
• Recommendations to Reparex. In order to improve their service and reassure potential customers, we would recommend that Reparex do the following:
  • Take a close look at the information they are providing to customers on their websites and correct inconsistencies and mistakes where possible.
  • Conduct long-term, pre-registered, placebo-controlled trials to determine the efficacy and safety of Reparex as a product that can reverse hair graying.
  • Be transparent with their before-and-after photos and encourage people to take multiple photos of different angles of the face so that it is possible to identify them as the same person.
  • Provide mechanistic data so we can understand exactly how Reparex works (in other words, what is the biological mechanism that their product supposedly affects?).
• Our Current Thoughts. Due to the points mentioned above, we cannot recommend Reparex as a product for reversing gray hair. The onus is on Reparex to provide clear information and clinical data to convince us that this product works.

What is Reparex?

Reparex is a brand owned by a company called BOOS Labs that was established in 1991. They create multiple products including the Against Grey Hair product range. Reparex state that Against Grey Hair “Restores your own hair color, bringing back that natural look”.^[3]Reparex, (no date), Reparex Against Grey Hair. Available at: https://reparexshop.com/usa/reparex-against-grey-hair/ (Accessed: 29 January 2023

Reparex says that their product “is an outcome of life-long research made by a well-known biochemist and doctor Oto Sova, M.D, PhD. He developed and created a unique enzymatic formula which fits all people and is 100% safe for the human body”.^[5]Boos Labs, (no date). How it works. Available at: https://forgreyhair.com/how-it-works (Accessed: 30 January 2023

Oto Sova has, according to the website “studied in several scientific centers in Europe and was a student of several Nobel Prize winners”.^[6]For Grey Hair, (no date), For Grey Hair. Available at: https://forgreyhair.au/blog.html (Accessed: 29 January 2023

Who is their target consumer?

Reparex has products aimed at treating gray hair for both men and women. The case studies on their website include 11 men and 6 women.

What products do Reparex offer?

The Reparex range, including prices and volumes, is tabulated below.

Product	Size	Price
Reparex Against Grey Hair for Men	150ml	$54.95
Reparex Against Grey Hair for Women	150ml	$54.95
Reparex Against Gray Hair for Beard and Mustache	150ml	$54.95

Table 1: Prices of Reparex products. Adapted from:^[7]Reparex, (no date), Reparex Shop. Available at: https://reparexshop.com/usa/reparex-against-grey-hair/ (Accessed: 27 January 2023

Reparex also offers anti-dandruff lotions, shampoos, and skin ointments aimed at psoriasis sufferers.^[8]Reparex, (no date), Reparex Shop. Available at: https://reparexshop.com/usa/reparex-against-grey-hair/ (Accessed: 27 January 2023 These however are not part of the Against Grey Hair Range.

How do they claim these offerings are unique?

Reparex claims that their product is not a hair dye as, according to their definition, “hair dye colors your hair from the outside, but Reparex changes the hair color from the inside. It restores the original hair color, just as your hair was before it became gray”.^[9]Reparex, (no date), FAQ. Available at: https://reparexshop.com/usa/faq/ (Accessed: 27 January 2023

Quite what they mean by ‘’…changes hair color from the inside.’’ isn’t clear, and the data to support their claim to this mechanism (not to mention evidence that the product actually changes hair color) is lacking. This makes it difficult to determine whether this product is actually unique.

What is their pricing?

As can be seen above, you’re looking at spending $54.95 a bottle for the specific product you want in the Against Grey Hair series, which should last you around a month.^[10]Reparex, (no date), Reparex Shop. Available at: https://reparexshop.com/usa/reparex-against-grey-hair/ (Accessed: 27 January 2023

As there don’t appear to be other products that claim to do what Reparex does, there is not much to compare the price to. But, compared to standard hair dyes, which can be very cheap at around $10, this is perhaps on the pricier side.

Product Science: Deep Dive

Firstly, let’s give a brief overview of how melanin is formed and cover some reasons why hair might turn gray.

Melanin is a type of material in your hair that gives it its color. There are two types of melanin (eumelanin and pheomelanin) and these are both created by special types of cells called melanocytes. Melanocytes are present in both the skin and hair whose primary job is to create melanin. Eumelanin is a darker pigment and is responsible for darker hair color, and pheomelanin is responsible for lighter hair color. An individual person’s hair color will be based upon a specific amount of each type of melanin and their genetics.^[11]Slominski, A., Wortsman, J., Plonka, P.M., Schallreuter, K.U., Paus, R., Tobin D. (2005). Hair Follicle Pigmentation. Journal of Investigative Dermatology. 124(1), 13-21. Available at: … Continue reading

In the hair follicle, melanocytes undergo a cycle of growth (proliferation) and rest, in tandem with the hair follicle’s own growth (anagen) and non-growing (telogen) cycles. Specialized stem cells called melanocyte stem cells are located in the bulge of the hair follicle, are activated at the start of the hair follicle growing phase, and supply melanocytes to the core part (the matrix) of the hair follicle. Melanocytes then undergo multiple divisions so that there is a  continuous store of melanocytes (and therefore melanin) in the bulb of the hair follicle.^[12]Nishimura, E.K. (2011). Melanocyte stem cells: a melanocyte reservoir in hair follicles for hair and skin pigmentation. Pigment Cell & Melanoma Research. 24(3), 401-410. Available at: … Continue reading 

Melanin is then packaged into a small ‘packet’ called a vesicle (or a melanosome) which is then transferred into the cells that make the actual substance of the hair follicle (matrix keratinocytes).^[13]Schlessinger, D.I., Anoruo, M.D., Schlessinger, J. (2022). Biochemistry, Melanin, In: StatPearls, Treasure Island (FL). StatPearls publishing. Available at: … Continue reading Matrix keratinocytes are cells found in the matrix of the hair follicle, where they are highly proliferative (actively undergo cell division) to form the hair shaft you eventually see as your hair. 

The synthesis of melanin involves specific biochemical reactions (called redox reactions) which are made possible  by a couple of enzymes called tyrosinase and tyrosinase-related protein (TRP). These enzymes are involved at each step of the production of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) or O2- as can be seen in Figure 2. Redox reactions are chemical reactions in which a compound can either lose an electron (oxidized) or gain an electron (reduced).^[14]Denat, A., Kadekaro, A.L., Marrot, L., Leachman, S, Abdel-Malek, Z.A. (2014). Melanocytes as Instigators and Victims of Oxidative Stress. Journal of Investigative Dermatology. 134(6). 1512-1518 … Continue reading

ROS are chemical compounds that contain oxygen and are therefore highly reactive, so they readily interact with the environment around them. These can cause an environment called oxidative stress which, among other things, can cause damage to melanocytes and other cells in the hair follicle.^[15]NIH, (no date), Reactive oxygen species. Available at: https://cancer.gov/publications/dictionaries/cancer-terms/def/reactie-oxygen-species (Accessed: 30 January 2023

However, the hair follicle has a natural defense against ROS -an enzyme called catalase. Catalase breaks down hydrogen peroxide over a series of chemical reactions (also redox reactions), resulting in the production of water and oxygen, and providing protection against oxidative stress.^[17]Goyal, M.M., Basak, A. (2010). Human Catalase: Looking for Complete Identity. Protein & Cell. 1(10). 888-897. Available at: https://doi.org/10.1007/is13238-010-0113-z

While there are in-built mechanisms in place for reducing oxidative stress, these can be dysregulated by old age, radiation, inflammation, and psychological/emotional stress. It has been found that there is an increase in oxidative stress and death (apoptosis) of melanin-producing cells (melanocytes) in individuals with gray hairs, as well as a reduction of key protectors against oxidative stress, such as Bcl-2 (and catalase which we will go into further below) and growth factors involved in melanocyte growth such as c-Kit. This reduction in melanocytes subsequently leads to less melanin in hair shafts, giving hair a gray appearance (Figure 3).^[18]Arck, P.C., Overall, R., Spatz, K., Liezman, C., Handjiski, B., Klapp, B.F., Birch-Madin, M.A., Peters, E.M.J. (2006). Towards a “free radical theory of graying”: melanocyte apoptosis in the … Continue reading 

A further study compared isolated growing hair follicles, dermal papilla cells (DPCs), and other specialized hair follicle cells from gray- and brown-haired donors.^[20]Wood, J.M., Decker, H., Hartmann, H., Chavan, B., Rokos, H., Spencer, J.D., Hasse, S., Thornton, S.J., Shalbaf. M., Paus, R., Schallreuter, K.U. (2009). Senile hair graying: H2O2-mediated oxidative … Continue reading The researchers showed that catalase and other enzymes responsible for maintaining a healthy redox balance within the hair follicle are reduced in graying hair, leading to a negative cycle of imbalance and subsequent oxidative stress. In addition to this, hydrogen peroxide was also found to be present in the graying hair follicle whereas it was not present in the brown hair follicle. Furthermore, the researchers found that tyrosinase activity, the enzyme essential for facilitating the synthesis of melanin, was reduced after melanocytes were incubated with increasing doses of hydrogen peroxide (Figure 4).

So, it is generally thought that oxidative stress can build up through different stressors in addition to the reactive oxygen species naturally produced through the synthesis of melanin. When oxidative stress builds up, it can reduce the activity of melanocytes and even induce them to die. In these circumstances as there is no longer enough melanin produced to provide keratinocytes with the natural pigment and hairs become gray.

But what does all this have to do with Reparex?

Reparex states that “as we get older hair turns gray due to a natural build-up of hydrogen peroxide in the hair follicles, which causes oxidative stress which oxidizes melanin and consecutively causes graying”. Then they claim that “Reparex removes Oxygen from oxidized colorless  melanin using the enzyme g-reductase which binds with silver nitrate. This results in restoration of melanin’s natural color”.^[22]Reparex, (no date), How does it work? Available at: https://reparexshop.com/usa/reparex-against-grey-hair (Accessed: 29 January 2023

While the statement above is an attempt to explain the mechanism of action of the Against Grey Hair products, it does not seem to fit with the current theories that state that we lose melanin rather than have colorless melanin within our hair. Additionally,  the information on their website is quite confusing and inconsistent,  so the only thing we can do is try to break the product down and see how it might work.

The two main ingredients in Reparex’s Against Grey Hair products are silver acetate and glucuronate reductase. Reparex claims that “glucuronate reductase…was able to remove the oxygen from hair melanine [sic] and gives it to silver nitrate”.^[23]Boos Labs, (no date), Product Information File. Available at: https://www.forgreyhair.co.uk/wp-content/uploads/sites/12/2022/09/PIF-FGH.pdf (Accessed: 27 January 2023 

So, let’s see what these ingredients might do…

Silver acetate…or is it silver nitrate?

Reparex uses the terms silver acetate and silver nitrate interchangeably throughout its website. While they are superficially similar chemical names, they are certainly not the same chemical. In their reasoning for including these chemicals, Reparex state that when they just used the glucuronate reductase by itself it “…took away the oxygen and the hair darkened, but after a while, the hair turned gray again, because the enzymes had no place to transfer the taken oxygen and so they put it back in the hair…therefore it was necessary to engage some ‘oxygen scavenger’ and thus the addition of a minimum amount of silver acetate. As a result, For Grey Hair has become fully functional and usable”.^[24]Boos Labs, (no date), The single best treatment for gray hair invented by Oto Sova. Available at: https://forgreyhair.com.au/httpswwwforgreyhaircombest-treatment-for-grey-hair.c128.html (Accessed: 30 … Continue reading

However, with regard to silver acetate, we weren’t able to find any evidence to suggest that it can bind to oxygen or react with oxygen. Furthermore, there does not appear to be any precedence for using silver acetate in hair products. 

Silver nitrate, however, can react with oxygen. Furthermore, it has been used as a hair colorant.  used daily, it slowly darkens or lightens the hair. So, perhaps there is some rationale for including silver nitrate ^[25]Guerra-Tapia, A., Gonzalez-Guerra, E. (2014). Hair Cosmetics: Dyes. Actas Dermo-Sifiliográficas (English Edition). 105(9), 833-839. https://doi.org/10.1016j.adengl.2014.02.003

Glucuronate Reductase

Glucuronate reductase is an enzyme that belongs to a family of oxidoreductases. Oxidoreductases are enzymes that facilitate redox reactions.^[26]Legesse, H.B., Assefa, B.E. (2021). Biological Application and Disease of Oxidoreductase Enzymes. Oxidoreductase. Available at: https://doi.org/10.5772/intechopen.93328 With regard to  Reparex, we can hypothesize that it might work by facilitating a redox reaction in which hydrogen peroxide present in graying hair gets broken down, therefore clearing it from the hair. Perhaps this would reduce oxidative stress and prevent damage to melanocytes. Even if this was the case, would this mechanism still work to replenish already lost melanocytes? Perhaps not.

In any case, as there is no actual mechanistic data, all we can do is speculate and hypothesize, but is there any clinical information about whether this product actually works?

Does Reparex work as a hair treatment?

Unfortunately, there is no clinical data associated with this product that can tell us whether it actually works. There are some case study before-and-after photos presented on the Reparex website; however, some of these appear to actually be just the same photo twice, and it’s impossible to tell if some of the before-and-after photos are the same person, even if there are some notable changes. 

Additionally, Reparex offers “2 Free Reparex products of your choice for and before and after photos from our customers”.^[27]Reparex, (no date), Reparex Against Grey Hair. Available at: https://reparexshop.com/usa/reparex-against-grey-hair (Accessed: 30 January 2023 The problem with only having before-and-after photos and an incentive to provide them, is that it’s more likely that only people who have positive responses to the treatment will post their results. Furthermore, it’s possible that there are a number of people who saw no improvement, that Reparex may have chosen not to show. This can be avoided with pre-registered clinical trials with disclosed patient numbers, as they will need to show details for all the participants regardless of whether they show a response to the treatment or not.

So, there is no clinical data and no mechanism of action data, meaning that if we did want to use it, we have to trust Reparex and its unconvincing before-and-after photos. But can we actually trust them?

Other than the confusing information on the website about their own product, Reparex also has some somewhat shaky information in their FAQs which leads us to question their overall knowledge about hair. An example is:

“Q: Does REPAREX reduce hair loss?

A: According to latest scientific research, hair loss is caused by a lack of elements such as nickel and iron. We cannot say which one of these is particularly missing for each individual therefore REPAREX cannot help your hair to grow again but we can assure you that it will not cause hair loss to start nor make it worse if you are already suffering from hair loss. Our product has no effect on hair loss.”^[30]Reparex, (no date), FAQs. Available at: https://reparexshop.com/usa/faq/ (Accessed: 29 January 2023

While vitamin and mineral deficiency can certainly contribute towards hair loss, in reality, it’s not the only way that hair loss can develop.^[31]Almohanna, H.M., Ahmed, A.A., Tsatalis, J.P. (2019). The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatology and Therapy. 9, 51-70. Available at: … Continue reading For example, androgenetic alopecia (AGA) can be caused by an overproduction or oversensitivity to androgens (such as dihydrotestosterone); telogen effluvium can be caused by multiple triggering events, including pregnancy; alopecia areata can be caused as a function of autoimmune dysregulation (to name a few).^[32]Alessandrini, A., Bruni, F., Piraccini, B.M., Starace, M. (2020). Common causes of hair loss – clinical manifestations, trichoscopy and therapy. Journal of the European Academy of Dermatology and … Continue reading

Is Reparex Against Grey Hair safe?

Reparex states that “REPAREX has been carefully tested according to the latest EC regulations for cosmetic products; this includes testing for heavy metal content, skin irritation, and any general harm. It has also been evaluated by independent Cosmetic Product Safety Assessors. Furthermore, REPAREX has also been registered at the Central Registration of Cosmetic Products in Brussels and according to its status as harmless it was released to the EU market as harmless and 100% legal.”^[33]Reparex, (no date) FAQ. Available at: https://reparexshop.com/usa/faq/ (Accessed: 29 January 2023

However, to our knowledge, there has been no published efficacy or safety data for this product, so we cannot say with certainty that this product is safe to use long-term. It’s also worth noting there are dozens of examples whereby short-term (i.e., 1-2 year) data suggested that a natural substance might be safe, only for long-term (i.e., 5-10+ year) data to show the exact opposite. One example: the effects of vitamin E and selenium supplements on prostate cancer. Short-term data suggested benefit, while long-term data showed these supplements doubled the rates of prostate cancer in men with already-adequate vitamin E and selenium levels.

Should I use Reparex?

You may consider trying out this product if:

• You are unhappy with your gray hair
• You do not want to use other hair dyes
• You are happy using products that have no efficacy or safety data
• You are ok buying a product from a company that has confusing and incorrect information on their website

You may be better placed however to just use a standard hair dye, which you can buy for a fraction of the price.

Recommendations to the company

We would recommend that Reparex look at the information that they are showing on their websites and make sure that it is consistent with (1) the actual ingredients in the product and (2) current scientific data. Furthermore, we recommend that Reparex conduct some mechanistic and long-term pre-registered clinical trials to determine the efficacy and safety of Reparex as a product that can reverse hair graying. Additionally, Reparex should address the issues with their before-and-after photos and make sure that they are not the same photos, and that people can be clearly identified as the same person.

Final thoughts

If you are comfortable trying products with zero published clinical or mechanistic data, and you do not want to use hair dyes, then Reparex might be something you could consider experimenting with. Otherwise, we do not recommend using this product in its current state.