Do hair growth inhibitors really work? Episode 57

Do those hair growth inhibitor products (the ones that say they let you shave less often) really work? This week Randy and I explain what to look for when shopping for a shave minimizing lotion.      

Show notes

Strange beauty science search terms

You’d be surprised at some of the search terms that lead people to our website. Randy reviews a few of the more amusing ones and we talk about where they might have come from…

  1. Rachael Ray panties
  2. Human hair clothing
  3. Mascara eating bugs
  4. Paris Hilton ptosis
  5. How to tell if a girls boobs are fake
  6. My head smells weird
  7. Yogurt as lube
  8. Why are women’s legs so attractive
  9. The very hairy best of hirsute
  10. Animal make-up
  11. Meat skin

Question of the week: Do hair growth inhibitors really work? 

Gail from Canada asks…How do hair growth inhibitors creams like Inhibitif work?

The biology of hair and hair growth

Before we talk about inhibiting hair growth we’ll give you some quick background about how hair grows. First there are two types of hair on our bodies:

  • Androgenic hair – the thicker, longer hair like you see on your scalp.
  • Vellus hair – the shorter, finer hair you find on your arms and legs.

Second, there are three phases of growth that each hair fiber goes through:

  • Anagen: This is the active or growth phase. Lasts from 2 to 6 years. The more time a hair stays in this phase, the longer it will grow.
  • Catagen: This is the transitional phase where the follicle renews itself. The hair becomes detached from the root but it continues to be pushed toward the surface. This phase lasts a few weeks.
  • Telogen: This is the resting phase where follicle is not producing any new hairs. The last hair to be produced by this follicle is pushed all the way out and will eventually fall out. This phase lasts up to a few months.
  • Exogen: This is a relatively new term that some sources are using to describe when the hair is actually shed.

Remember that you have hundreds of thousands of hairs on your body and at any given time some of those hairs are in each of these phases.

The chemistry of hair growth inhibition

The chemicals that affect hair growth typically fall into one of three classes “cytotoxic compounds that kill the hair cells as they grow, antiandrogens which screw with the hormones that control hair growth; and drugs that close potassium channels which stunts hair growth.

I know that Gail asked specifically about the Inhibitif product but we’ll approach this by discussing the different “so callled” active ingredients used to inhibit hair growth and then we’ll discuss products along the way. So here’s how this will work: we’ll explain what the ingredient is, how it works, we’ll review the evidence for it and then give some example products. And by the way there are a TON of these products on the market. Most from very small companies that fly under the radar, by the way. Which is a red flag: Don’t you think it was really safe and effective, you’d see products from the major, reptuable cosmetic companies? Why would manufacturers, expecially those who are in the hair removal business, like makers of Nair (which is made by Church and Dwight) just ignore this market? Probably because these ingredients don’t really work or their safety hasn’t been established! Yes, that’s sort of circumstantial evidence but my point is that these shave minimizing products are not such a sure thing.

So let’s talk about active ingredients roughly in order from least effective to most effective.

Non-active actives (Epilation or waxing)

What is it:
There are a number of products on the market that are really just depilatories disguised as hair growth inhibitors. They don’t contain any ingredients which have the potential to slow hair growth but you might not understand this from the way the products are advertised.

How does it work:
These products simply remove hair by dissolving it with a high pH caustic formula or they pull the hair out with waxes.

Is there evidence:
You have to read the claims on these products carefully because they may imply that they inhibit hair growth when they really don’t. They will certainly work as a depilatory if they contain ingredients like calcium hydroxide and calcium thioglycolate. These dissolve the hair below the surface of your skin so they do take a while to grow back but the rate of hair growth is NOT affected.

Products of this type include Enleve and Epil Stop.

Herbal extracts

What is it:
This is another type of non-active active or at least a non-specified active. There are a couple of products on the market that simply claim to slow hair growth with “herbal extracts.”

How does it work:
As you can imagine, such a vague description makes it impossible to determine a potential mechanism for how the product MIGHT work and the only evidence that’s available are the claims made by the company marketing the product. Again, for the most part, these are companies that are too small to trigger any action by the FDA or any other regulatory agency.

Is there evidence:
One example is the product “Kalo” by Nism which claims that it’s “organic extracts” and sulphur inhibitors “prevent hair from regenerating.” The company does provide a link to a claims support study, but as far as I can tell, the study was done on waxed skin with no control. We know that waxing alone can reduce hair growth so this study does NOT prove that Kalo does anything

Another example of the herbal extract approach is Jergens Naturally Smooth Shave Minimizing Moisturizer and it DOES identify which extract is uses: it’s Sanguisorba Officinalis Root Extract. Strangely enough, the only scientific paper I could find saying that this extract affects hair growth states that it reduces hair LOSS by increasing the amount of time the hair shaft spends in the anagen or active growth phase. (Wouldn’t that make you shave more often?) Now, Jergens is owned by Kao which is a big company so at first glance this might appear to be a legitimate shave minimizing product but since there’s no apparent evidence that it works and considering that it’s been taken off the market, I don’t really think so.  The bottom line here is that I would avoid any of these products that only tell you they work by “herbal extracts.”

Fruit enzymes (Papain)

What is it:
Although not all products disclose their ingredients online, it appears that several of them use a protein-cleaving enzyme called papain which is cystine protease. It comes from papaya and other fruits.

How does it work: 
Some enzymes of this type have been shown to cause apoptosis of follicular papillae. Essentially that means that they kill the cells before they can reproduce. If the ingredient kills off enough hair growth cells, you’ll have fewer hairs and the hairs that do grow out will most likely be thinner and less visible.

Is there evidence: 
Despite this theoretical mechanism, there doesn’t seem to be any clear scientific evidience that papain-based products inhibit hair growth. The closest support we could find was one study showing that Trypsin, a similar enzyme, has shown to reduce hair growth in mice that had been waxed.

And even if the enzyme really works, it’s difficult to deliver it properly because these enzymes are not very stable. There are a few patents related to stabilzing enzymes in hair removal products but basically you have to mix two systems together for it to work. If you’re buying a single bottle of an enzyme based product it’s unlikely that there’s enough enzyme present to have much effect.

There’s also the question of safety – although shave minimizing products are not recognized as a drug category, the FDA has taken action against other topical drug products that are based on papain. For topical wound healing products with papain there have been reports of not only allergic reactions but anaphactic shock, low blood pressure, and rapid heart rate which prompted the FDA to proclaim that all topical drug products containing papain require FDA approval. Of course since these hair growth products aren’t making the same kind of would healing claims, they aren’t technically affected by this action. Still, it does raise the question of whether or not these products are safe. (

Of course all that doesn’t deter companies from selling enzyme based shave minimizing products – there a number of these on the market:

Ultra Hair Away
Derma Nude – which has this crazy scientific explanation: it suppresses hair regrowth 5 ways: “(1)Unwind keratin, (2) break keratin apart and separate it from the matrix (3) perforate the cystine, (4) work below the growth plate at the double sulfa helix bond. (5) prevent cystine to cystine bonding at the active phase of hair growth.”


What is it: 
Next up is dihydromyricetin which is a type of flavonoid compound derived from certain plant species such as the Katsura tree which is native to China and Japan. It’s used in traditional Chinese medicine and recently it’s been touted as a possible hangover cure.

How does it work: 
Supposedly, according to the companies that sell this stuff, Dihydromyricetin inhibits the IGF-1 receptors in hair follicles. (IGF stands for Insulin-like Growth Factor.) IGF-1 is thought to prevent death of cells in the follicle, which would keep hair growing longer. So, if you can inhibit IGF-1, you can theoretically prevent hair from growing.

Is there evidence: 
However, we couldn’t find any scientific evidence that dihydromyricetin really works this way. The technical literature that reviews of IGF-1 receptor inhibitors makes no mention of this compound so the lack of published evidence makes us very skeptical.

To make things worse, care must be taked when using compounds that really CAN inhibit IGF-1 because similar receptors regulate growth of other tissues as well. According to one source, there’s concern that such an inhibitor could mess with the insulin receptors which could cause serious health issues.

The best evidence we could find is a study by a company selling dihydromyricetin, called Telocapil, which shows 60% reduction in hair growth. The good news is that the study was done vs placebo. But it was a small test, only 15 people and I can’t tell from the description of the study if both test and control side had depilation. As we said before, even just waxing can slow hair growth. So, I can’t put a lot of faith into this…nonetheless there are a few products on the market using this technology.

Dermadoctor Gorilla Warfare Hair Minimizing facial moisturizer

Inhibitif not only uses dihydromyricetin but it also uses another ingredient which we’ll discuss next. Actually it’s a little confusing because there are 4 products in the line which all contain D but only the Advanced Hair-Free Serum contains both dihydromyricetin and lauryl iso-quino-linium bromide.

I found a VERY detailed review on a website called “Ingredients” which is written by “Louise” a pHD in biochemistry, she gives a good scientific analysis complete with references so you can check the facts yourself.

Lauryl isoquinolinium bromide

What is it:
Chemically speaking this is a quaternary ammonium compound. This particular isoquinolinium derivative is known to be a disinfectant and it was previously used in over the counter acne products but since the FDA has restricted it’s use due to lack of safety data. By the way, in Japan, it’s allowed in products but only at a maximum concentration of 0.05% active level in finished goods. And if there’s a lack of safety data I’m not sure that it’s the best ingredient for hair removal anyway.

How does it work:
We couldn’t find a clear mechanism described anywhere in the technical literature. Based on the product sheet for one product and the understanding that isoquinoline can be cytotoxic, it appears that it kills hair follicles that are in the anagen phase. One patent described it’s action as “choking” the hair root.

Is there evidence:
Lipotek, one of the suppliers of Lauryl isoquinolinium bromide sells it in a blend which they call Decelerine. (In addition to the isoquinolinium it contains Pseudoalteromonas Ferment Extract, Aloe and Allantoin. According to the study conducted by Lipotek, a 3% Decelerine gel used for 30 and 60 days and showed statistically significant reduction in hair growth of about 15% in density (hairs per sq cm) and 30% in length. 75% of the 20 panelists said it decreased beard regrowth. Here’s the link: It contains 3.65% LIB. FYI, the amount tested in this study was 0.1% which is twice the allowed limit in Japan. So…we have a compound without a clear mechanism, with the only efficacy data is a small test conducted by the supplier, AND the FDA has apparently raised questions about its safety. This doesn’t sound like the ideal active ingredient either but it is found in several products.

Bluebeard’s Revenge
Nu Skin Dividends Aftershave balm


What is it:
Eflornithine hydrochloride is the only prescription drug that’s currently available to treat hirsutism. (Compared to everything else we’ve talked about it’s the only chemical that’s also effective against African Sleeping Sickness.)  It’s only approved for use on around the face and under the chin.

How does it work:
We mentioned there are 3 primary ways that hair growth inhibitors work – actually there’s a fourth: this drug irreversibly inhibits an enzyme that’s involved in controlling hair growth.

Is there evidence: 
Yes, it’s clinically proven. However, it’s only approved for use around the face and under the chin and you need to use it with another method like shaving. It’s only been studied for use on the face if you start using it over your entire body that’s a much larger surface area and a much higher dosage. Even then it doesn’t help everyone. 42% saw no improvement. About 55% saw improvement or marked improvement. 5% were “almost clear” of facial hair. And 8 weeks after you stop using it, hair growth is likely to return to the same level. And more bad news – one of its side effects is acne.


The Beauty Brains bottom line

So the bottom line for Gail is that these shave minimizing products are sketchy at best. There’s not a lot of evidence which these products work – and if they do work they may require you to wax your skin first. An even bigger issue is that are some serious questions about the safety of some of these active ingredients. That’s probably why there are no shave minimizing products from any major cosmetic company. Of course, there are some shifty companies out there who are more than willing to sell you an over-priced depilatory that’s disguised as a hair growth inhibitor. So, as with many other products which are borderline drugs, caveat emptor – let the buyer beware. Of course you can ask your doctor for a prescription for Vaniqa but that won’t help with your hairy legs.

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