Rosemary oil for hair growth? How to spot bad science

Summary

This video script delves into the efficacy of rosemary oil for hair growth, scrutinizing a study that claims its effectiveness rivals minoxidil. The host expresses skepticism, highlighting methodological flaws, data inconsistencies, and the unreliability of relying solely on mechanistic reasoning. The script underscores the importance of critical assessment of scientific studies, the limitations of peer review, and the necessity of clinical trials. It concludes by advising viewers to approach rosemary oil with caution and consider more established treatments for hair loss.

Takeaways

• 🌿 Rosemary oil is often cited as a natural treatment for hair growth, with some claiming it's as effective as minoxidil, a common hair loss treatment.
• 🔬 A 2015 study frequently referenced for supporting rosemary oil's efficacy has been criticized for methodological issues, casting doubt on its reliability.
• ⚖️ The study compared rosemary oil to a 2% minoxidil solution, which is weaker than the 5% solution typically recommended by dermatologists.
• ⏱️ The study's duration of 6 months is considered too short to accurately assess the efficacy of hair growth treatments.
• 📊 The study's data, including identical baseline and 3-month hair count numbers, contained errors that raise questions about the validity of the results.
• 📝 Peer review, while intended to ensure scientific quality, is not foolproof and can sometimes allow flawed studies to be published.
• 🌐 The study has been cited numerous times, indicating that even peer-reviewed articles may not critically assess the sources they reference.
• 🍃 Rosemary oil's potential mechanisms for hair growth, such as increased blood flow and antioxidant properties, are theoretical and not conclusively proven.
• ⚠️ The variability in rosemary oil's composition due to factors like growing conditions and extraction methods can affect its potential efficacy.
• 💧 The study suggests a dilution ratio of 1:161 for rosemary oil, highlighting the need for caution to avoid irritation, especially given reports of increased scalp itching and dandruff among users.

Q & A

Is rosemary oil considered a scientifically backed treatment for hair growth?

While some studies suggest rosemary oil could be as effective as minoxidil for hair growth, the evidence is not conclusive due to methodological issues and inconsistencies in the research.

What are the potential mechanisms by which rosemary oil might promote hair growth?

Rosemary oil is thought to potentially increase blood flow to hair follicles and act as an antioxidant, neutralizing free radicals that could contribute to hair loss.

What are the common issues with the study that compared rosemary oil to minoxidil for hair loss treatment?

The study has been criticized for using a low concentration of minoxidil, having a short duration of treatment, and presenting suspiciously identical data points that raise questions about the accuracy of the results.

How does the peer-review process in scientific journals work, and what are its limitations?

Peer review involves other scientists evaluating an article's quality before publication. Limitations include variable quality, potential bias, and the fact that less popular topics may not receive as much scrutiny.

Why is it important not to rely solely on the abstract of a scientific paper for understanding its findings?

Abstracts are summaries that may not include critical limitations or may overstate results. They should be used to determine if the full paper is relevant, not as a substitute for reading the entire study.

What are some red flags in the rosemary oil study that question its reliability?

Red flags include identical data points that should logically differ, discrepancies in figures, and missing methodology for collecting certain data, suggesting potential flaws in the study's execution and reporting.

How do seasonal variations and other factors impact hair growth, and how might they affect the results of hair loss studies?

Seasonal changes, stress, and other factors can cause natural fluctuations in hair growth and shedding, potentially leading to misinterpretations of treatment effects in studies.

What is the role of mechanistic reasoning in evaluating the potential efficacy of treatments like rosemary oil for hair loss?

Mechanistic reasoning can suggest how a treatment might work but is not definitive evidence of efficacy. It's important to consider clinical trial results, which account for the complex interplay of mechanisms in the body.

Why might some people experience increased hair loss or scalp irritation after using rosemary oil?

Rosemary oil contains allergens and irritants like camphor, carnosol, and cineole, which could potentially exacerbate hair loss or cause scalp irritation for some individuals.

What are some alternative treatments for hair loss that are recommended over rosemary oil based on the evidence presented?

Proven treatments like minoxidil are recommended over rosemary oil due to stronger clinical evidence supporting their efficacy. It's also advised to consult a healthcare professional to address potential underlying causes of hair loss.

Outlines

00:00

🌿 Rosemary Oil's Effectiveness on Hair Growth

The paragraph introduces the topic of whether rosemary oil is scientifically proven to aid hair growth. It mentions that many doctors and scientists support the claim, with studies suggesting rosemary oil can be as effective as minoxidil. The paragraph also discusses the science behind rosemary oil's potential benefits for hair growth, particularly in treating androgenetic alopecia. It highlights the importance of consistency in applying rosemary oil and the need for at least six months of use to gauge its effectiveness. The speaker also expresses skepticism about a frequently cited study, hinting at flaws in the research that others have overlooked.

05:00

🔍 Critical Analysis of Rosemary Oil Study

This section delves into the critical analysis of a study that compares rosemary oil to minoxidil for treating androgenetic alopecia. The study, published in a peer-reviewed journal, has been widely cited despite its questionable quality. The paragraph discusses the process of peer review in scientific publishing, explaining how it is intended to ensure research quality but is not foolproof. It points out issues such as less scrutiny for less popular topics, potential biases, and the variable quality of peer review. The speaker emphasizes the importance of reading scientific papers carefully, especially the methods and results sections, to assess their reliability.

10:03

🕵️‍♀️ Identifying Flaws in Scientific Research

The speaker identifies specific issues with the rosemary oil study, including the use of a low concentration of minoxidil, which is a known treatment for hair loss. They also question the study's short duration, as hair growth cycles can span years, making a six-month study insufficient for a reliable assessment. The paragraph discusses the unreliability of before-and-after photos and the implausibility of the hair count numbers reported in the study. The speaker suggests that the study's methodological issues extend to other aspects of the research, casting doubt on its overall validity.

15:04

📊 Understanding Hair Growth Data and Its Limitations

This paragraph further scrutinizes the data presented in the rosemary oil study, pointing out inconsistencies and errors in the reported hair count numbers. It discusses the small differences in hair count between the treatment groups and how these differences are not statistically significant. The speaker also considers seasonal variations in hair growth and how they might affect study outcomes. The paragraph highlights the potential for perception bias in self-assessments of hair loss and the unreliability of anecdotal evidence in evaluating treatment efficacy.

20:07

📚 The Role of Mechanistic Evidence in Hair Loss Treatments

The paragraph discusses the limitations of relying on mechanistic evidence alone to support the use of rosemary oil for hair loss. It contrasts this with clinical trials, which provide more concrete evidence of a treatment's effectiveness. The speaker explains that even promising lead compounds with strong mechanistic evidence often fail in clinical trials, emphasizing the importance of actual clinical data over theoretical benefits. They also address the variability in rosemary oil composition and the potential for allergens and irritants to counteract any benefits, concluding that rosemary oil is not a reliable treatment for hair loss.

25:08

💡 Alternative Hair Loss Treatments and Recommendations

In the final paragraph, the speaker advises against using rosemary oil for hair loss due to the lack of compelling evidence and recommends consulting a healthcare professional for proven treatments. They suggest that hair loss may be symptomatic of an underlying condition that requires medical attention. The paragraph also touches on the importance of using proven treatments like minoxidil and being cautious of remedies that delay the use of more effective interventions. The speaker concludes by directing viewers to additional resources for understanding hair care science and the evaluation of ingredient efficacy.

Keywords

💡Rosemary oil

Rosemary oil is an essential oil extracted from the rosemary plant, known for its various pharmacological properties. In the context of the video, it is discussed as a potential treatment for hair growth, with some studies suggesting it may be as effective as minoxidil, a common hair loss treatment. The video script references a 2015 study that compared the effectiveness of rosemary oil to minoxidil for treating androgenetic alopecia, suggesting that rosemary oil could be a natural alternative.

💡Minoxidil

Minoxidil is a medication originally developed for hypertension but is now widely used to treat hair loss. It is an FDA-approved topical treatment that promotes hair growth by improving blood flow to the hair follicles. In the video, minoxidil is compared with rosemary oil in terms of effectiveness for treating hair loss, with the script highlighting a study that suggests rosemary oil may be just as effective as minoxidil 2%.

💡Androgenetic alopecia

Androgenetic alopecia, also known as male or female pattern baldness, is the most common type of hair loss. It is characterized by a receding hairline and thinning of hair on the scalp. The video discusses this condition as the focus of the study comparing rosemary oil and minoxidil, aiming to determine the efficacy of these treatments for managing androgenetic alopecia.

💡Scientific proof

Scientific proof refers to evidence supporting a claim or hypothesis that is based on rigorous scientific research and data. The video script mentions that there is scientific proof that rosemary oil works for hair growth, citing studies and expert opinions to back this claim.

💡Dermatologists

Dermatologists are medical professionals specializing in the skin, hair, and nails. In the video, dermatologists are referenced as authorities on hair loss treatments, with the script suggesting that rosemary oil could be beneficial for patients suffering from androgenetic alopecia based on dermatological assessments.

💡Peer-reviewed

Peer-reviewed refers to the process where scholars or experts in a particular field evaluate the work of their colleagues to judge their research quality. The video script discusses the importance of peer-reviewed journals in scientific research and how they are generally considered higher quality sources of scientific information. However, it also points out that peer review is not always perfect and can sometimes allow flawed studies to be published.

💡Abstract

An abstract is a brief summary of a research paper, highlighting the main points. The video script warns against relying solely on abstracts when assessing scientific studies, as they may not provide a full picture or critical assessment of the research. The abstract of the study discussed in the video is critiqued for potentially misleading readers about the effectiveness of rosemary oil for hair growth.

💡Clinical trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. The video emphasizes the importance of clinical trials in determining the efficacy of treatments like rosemary oil for hair loss, as they provide empirical evidence of how a treatment performs in actual patients.

💡Mechanistic logic

Mechanistic logic refers to reasoning based on the biological or chemical mechanisms through which a substance is thought to have an effect. The video discusses how relying solely on mechanistic logic to predict the effectiveness of a treatment like rosemary oil can be misleading, as it does not account for the complex interactions within the body that may influence the treatment's actual effectiveness.

💡Dilution

Dilution in the context of the video refers to the process of mixing a concentrated substance, like rosemary oil, with a carrier oil to make it safe for topical application. The script mentions that rosemary oil should be diluted before use to avoid potential irritation or allergic reactions, which is a common practice when using essential oils.

Highlights

Rosemary oil is suggested by some doctors and scientists to be as effective for hair growth as minoxidil.

A 2015 study indicated that rosemary oil could be beneficial for patients with androgenetic alopecia.

Topical application of diluted rosemary oil on the scalp may be as effective as minoxidil, according to some studies.

For rosemary oil to potentially regrow hair, consistent use for at least six months is recommended.

The study often cited for rosemary oil's efficacy has been criticized for its methodology and data integrity.

The peer-review process is explained, highlighting its importance and limitations in scientific research.

The study comparing rosemary oil to 2% minoxidil has been widely cited but contains significant flaws.

The use of 2% minoxidil in the study is questioned, as 5% is more commonly recommended for hair growth.

The study's six-month duration may be too short to accurately assess hair growth treatments.

Discrepancies in the study's data, such as unchanged hair count numbers, raise doubts about its reliability.

The study's abstract may be misleading, suggesting better results than the full paper supports.

The potential for seasonal variation and other factors to affect hair growth is discussed, impacting study results.

The study's self-assessment results are questionable, with all participants reporting improved hair loss.

Mechanistic reasoning is discussed as an insufficient basis for the efficacy of rosemary oil without clinical support.

The potential for rosemary oil to block 5-alpha reductase is mentioned, but the study has limitations.

The importance of consulting with healthcare professionals for hair loss treatment is emphasized.

Dilution of rosemary oil is advised to minimize potential irritation and allergic reactions.

The video concludes that rosemary oil is not recommended for hair loss treatment based on the available evidence.

Transcripts

hey chicken sauce Michelle here

is rosemary oil a natural science backed treatment for hair growth?

according to a lot of doctors and scientists and trichologists across the internet yes

there is scientific proof rosemary oil works as well as minoxidil

here's the science behind why rosemary oil and rosemary water work to grow your hair

2015 studies showed rosemary oil to be just as effective as minoxidil

best and worst hair loss treatments according to dermatologists

my take away from this is that rosemary oil can be beneficial for patients suffering from

androgenetic alopecia

use topical rosemary oil diluted onto your scalp studies show it's as effective as minoxidil

here are three derm approved hacks for using rosemary oil to help regrow your hair

yes it can help but you have to be consistent with use for at least 6 months to determine

whether it works for you or not

and it all seems to come down to this one study

for a long time I didn't look into it I just kind of assumed it was legit because everyone

cited it

anyway it turns out I shouldn't have assumed that because when I finally looked at the

study

[exhale] I really wasn't prepared for how bad the study

was

so today I'm going to explain why

I'm going to talk about what the science actually tells us about rosemary oil and hair loss

whether it's safe to try

and give you some tips for critically assessing studies so you don't fall for bad science

and as a bonus you'll also understand how a peer reviewed journal published this AI

generated rat… thing

so this is the study that everyone is citing

rosemary oil versus minoxidil 2% for the treatment of androgenetic alopecia a randomized comparative

trial

it was published in skinmed which is a peer-reviewed journal and peer reviewed is generally considered

higher quality when it comes to scientific sources and it kind of is but it also really

isn't

to understand peer review we need to talk about how science works

back in the day when scientists looked like this to do science you would just

poke around some random stuff

find something interesting

science was pretty new back then so everyone was just discovering stuff everywhere

you would go tell your scientist pals about it at your science club meetings

they'd clap or argue with you

some of them would build on your discoveries in their research

you might write a book about it or get an article published in a magazine which in science

is called a journal

scientists would clap or argue with you

if they really didn't like it they might burn down your house

what are you doing

why is the door locked

but after a few hundred years people had discovered a lot of stuff so science had gotten a lot

more complex

a single journal editor didn't know everything about the subject anymore

so to work out which articles were good enough to publish they would ask other scientists

who knew more about that topic to weigh in

by the 1960s with super advanced things like photocopiers this process of peer review which

is just getting other scientists to decide if your articles were good or not this became

way more structured

these days the general process is

you do some research

you write an article and you send it to a journal

the editor checks that it mostly looks okay

if the research is important enough (that is going to come up again later) and if it

matches the journal topic

if yes they send it to usually two or three scientists who specialize in your area

these reviewers will check things like whether the equipment you're using will actually work

for what you're doing

whether your conclusions make scientific sense with what we already know from all of the

other studies out there

the reviewers send feedback to the editor and your article will be accepted or rejected

usually if it's accepted you'll still have to make a few changes

then your paper gets published

yay

after the paper gets published then there's post publication review which is where other

scientists will comment on your work or try to repeat your experiments

papers might end up corrected or retracted

it might end up compared to to other studies in reviews and textbooks and add to our general

body of scientific evidence

that is the less complicated established science that you might get taught at school and university

now this system is generally pretty good or at least it's probably one of the better systems

for building scientific knowledge what we know about how the world works

but it is really far from perfect

here are some of the big issues with peer review and this is a very incomplete list

less popular topics aren't scrutinized as much

plenty of dodgy papers get through and it is especially the case with an area like beauty

where a lot of the most rigorous research never gets published

I talked about this on my video on whether retinol is a scam

so there is not a lot of replication and not a lot of scientists are discussing and critiquing

the studies that do come out

plus peer review isn't really rewarded much peer reviewers aren't paid or recognized when

they do good peer review

peer review is anonymous and voluntary so the quality is pretty variable and it tends

to take a really long time

if a reviewer is checking a paper that they know probably isn't going to have a lot of

people reading it they might not take it as seriously maybe they won't read it super closely

peer reviewers can also be biased they might not read it as critically if one of the researchers

is really well known in the field or if they come from a prestigious institution just because

you would expect them to do good research

it's actually a really well-known hack for getting papers published quickly with minimal

revisions just stick a well-known author on there

it's one reason why there's so many examples of papers now from high-profile authors being

retracted for blatant issues like bad Photoshop

there are also dodgy journals that might not actually do peer review they just don't bother

sending the papers out for peer review they just put it through a process and tick it

off

now a dodgy journal doesn't mean that the study is automatically bad

it just means that you don't know if it's actually being peer-reviewed properly

at the same time a good journal doesn't mean that the study is automatically reliable

it's just that hopefully the obviously dodgy stuff is more likely to have been weeded out

so all of this just means that you have to be really careful when you're looking at a

scientific paper you can't just take what it says at face value you need to read the

whole thing slowly and carefully to work out if you should actually trust what it says

and this brings us to the next problem with papers - a lot of the time you might not actually

be able to read the full thing

lots of papers are behind paywalls and it is a pretty crappy system because the journals

don't pay for the research it's taxpayers or industry the peer reviewers review for

free and the authors usually have to pay for the journal to publish the paper

but then the journal or the publisher gets to charge people to read it and no the authors

do not get royalties

there are regulations coming in to make government funded research publicly available but it

is an ongoing process

but the part that is always free to read is this which is called the abstract

it's meant to be a summary of the paper and I think it's what a lot of people were basing

their rosemary oil opinions on without reading the full actual paper

but this is a trap

it is the most common trap with reading studies

never trust the abstract

this article I cowrote lists a whole bunch of traps but this one is the biggest

you're really just meant to use the abstract to work out if you should read the rest of

the paper if it's relevant to what you're researching

the abstract is really short they can't include a lot in there and you won't be able to critically

assess if what they're doing is actually making sense

it'll be missing a lot of the limitations of the study and the authors probably only

included the results that they wanted to highlight

and abstracts are usually not an accurate summary a lot of the time it's treated like

it's advertising for the rest of the paper to make you want to read the full study

the abstract is the first thing that journal editors and reviewers will see

well after the title and the authors

there are more papers being submitted than can actually be published so research that

comes across as more important is going to be more likely to be published so if you read

a lot of papers you will notice this pattern which is the abstracts usually hype up the

paper a bit too much

so think of the abstract as like the two sentence synopsis of a movie

like this sounds quite promising

this sounds reasonably straightforward to understand

this doesn't sound like an incredible work of genius

and this paper's abstract actually sounds pretty good

there's a total of 100 people which is a lot for a cosmetic study

more subjects means more repetition so the results are less likely to be a fluke

the treatments were used for 6 months which seems like a reasonably long time

rosemary oil also isn't being tested on its own it's being compared with minoxidil which

is one of the most popular hair loss treatments

this isn't quite as good as comparing it against a placebo treatment which has no active ingredients

but a lot of cosmetic studies just use the treatment on its own so again this is a promising

sign

now the results part of the abstract also sounds really impressive

"both groups experienced a significant increase in hair count at the six-month end point"

"no significant difference was found between the study groups regarding hair count either

at month 3 or month 6"

a word of warning here in science significant doesn't mean significant like there was a

lot more hair it basically means that statistically the the increase is pretty likely to be because

of something actually happening here rather than because of random variation

significant doesn't tell you about the size of the increase it could still be really small

like just one extra hair

scientists sometimes use words a bit weirdly it is another of the many traps that you can

fall into when reading papers

so if this abstract was all that you read and you assumed that it was accurate then

rosemary oil does sound really promising

so let's ruin it all by

reading the actual paper

here are the standard parts of a scientific paper

the most important parts to read are the methods and the results because those tell you what

the paper is actually about what original research the authors did

it is the whole point of the paper

the problem is that these are usually the hardest parts of the paper to read and evaluate

they're more technical it's where you get complicated words and numbers and symbols

and you do need to know a bit about the topic already to be able to assess these to any

proper level

the abstract introduction discussion and conclusion are much more friendlier to read they mostly

have normal words and they tell a nicer story

but they are the author's interpretations of what they found so those are going to be

a bit more subjective and more liable to spin

and if the interpretation here is sus that is a huge red flag but before we can judge

whether or not it is sus we need to look at what it is we're interpreting

now all of this sounds really intimidating like you have to be an active researcher to

spot bad science but I don't think that's actually the case

one thing I've noticed in my 12 years of interpreting and talking about beauty science is that a

paper that has really big problems with the methodology usually will mess up in other

places too

so you don't really need to be that familiar with experimental methods to be able to flag

a paper as sus

as a paper that you probably don't want to take too seriously

and this paper is a really good example

what made me go and read this paper in more detail is coming across a reel on Instagram

from Dr Leona Yip who is an Australian dermatologist

she pointed out some of the problems with this paper and some other dermatologists have

pointed them out too

a lot of people don't realize that dermatologists they don't just look at skin conditions they

also look at hair and nail conditions or at least they look at the bit that is living

which is very much the bit that's involved in hair loss

problem one 2% minoxidil

minoxidil is one of the best studied treatments for hair loss and that's why this paper sounds

so impressive

but the detail here is 2%

the vast majority of dermatologists would recommend at least minoxidil 5% to grow hairs

because 2% is just too weak

I honestly don't even remember myself when I had asked a patient to use minoxidil 2%

in the last 10 years cos I think they'll be quite disappointed

we know that 5% minoxidil has much better efficacy when compared to 2% minoxidil so

rosemary oil is really compared against the weaker treatment

problem two is the duration

6 months does sound like a long time but it's actually not a long time for hair growth

hair grows in a cycle and the average length is years

so 6 months is actually considered really early

it's unreliable to assess any treatment efficacy as early as 6 months so I suspect if we looked

at the 2-year mark minoxidil 2% will likely be more effective than rosemary oil

but like I said there are more general red flags in the study as well

here's one that I think anyone can spot

look at the sample before and after photos they're not exactly impressive

I think this really reinforces what the dermatologists were saying you just don't really expect that

much of a result after 6 months with 2% minoxidil

the different angle and lighting for minoxidil is pretty weird and it's kind of hard to work

out what you're looking at it looks like it might be a bit closer up

but the thing that really blew my mind and stopped me from taking this study as evidence

of anything was when I saw the actual hair count numbers

here's the baseline hair count numbers at the start of the trial and here is what they

are at 3 months

they are exactly the same numbers

this has to be a typo it is basically impossible to get the exact same mean and standard deviation

for two groups of 50 people 3 months apart

you probably couldn't even get that an hour apart

and whoever made the graph from the data didn't see an issue with these numbers

they used them in the graph as well

the baseline and month three numbers are exactly the same

and obviously you are allowed to have typos it doesn't mean that the study is automatically

bad I mean I have typos all the time in my posts I can't really judge

but these are two of their key data points there are only six numbers that really matter

in this whole study they are the whole point of the study and two of them are wrong

can we actually trust the other four numbers?

this is the sort of thing that should be picked up immediately in peer review but this is

a paper that has four authors who all supposedly looked over it and OK'ed it both in the results

part and in the graph

it also supposedly has peer reviewers who looked at it and none of these people corrected

it

if I was a peer reviewer for this article I would be asking to see the raw data and

checking all their calculations

and right now I've been assuming that the month three numbers are the ones that are

wrong but it could actually be the baseline numbers that are wrong

if it's the baseline numbers those are the ones that the whole "experienced a significant

increase in hair count at the 6 month endpoint" result is based on

I haven't found any corrections of this or any indications that anyone has reached out

to the researchers and clarified what is going on even though this has been cited 93 times

as of February 2024

we will come back to this later

okay so every time I look at this paper I just see more issues and and I'm not that

great at stats and I haven't gone through every single word really carefully so I'm

sure there's still tons of stuff I've missed

if you take the means of these two you get 24.08 not .03

16 plus 13 out of 100 is 29% not 21%

figures 5 and 6 are for greasy hair and dandruff but they are exactly the same

well the formatting is like a few pixels off

but if you look at the text dandruff should have way lower numbers they should be close

to 16% so they've just messed up the figure

these figure references are just wrong figures five and six aren't about scalp itching that

is actually meant to be figure seven

and you don't use a rating scale for depression to measure hair loss you just don't

depression and hair loss are completely different medical conditions

and this all just really highlights what I was saying before a paper with serious methodological

issues tends to have a lot of other issues and you don't need to be able to spot all

of these to know that this paper isn't reliable

and again it's not like having some typos completely invalidates the paper there are

lots of good papers out there that might have mixups with figures that might happen during

the final formatting and then the journal will issue a correction and everything is

fine

but if there's just a whole bunch of issues like there are here that is a huge red flag

that something is just not right

and some of these especially the calculation errors

you don't have the full data set available so you just have to kind of trust that they

did the calculations correctly and I mean

now even if we assume that these numbers for baseline and month six are correct it is still

really not that impressive

if we look at the absolute numbers the average difference here is either six or two hairs

this is a group where the standard deviation is about 50 hairs that means if you take the

middle 2/3 of people there is about 100 hairs difference between them six or two hairs is

just so small

and this graph shows how small this difference is if you just had to eyeball this graph and

look at the difference between these columns there just isn't really a big difference at

all

as a percentage the rosemary group increased by 5.5% minoxidil increased by 1.6%

plus here is the thing about hair the amount of hair that we have on our heads will naturally

fluctuate

that's because there are three stages of hair growth which are called anagen catagen and

telogen

the hairs on our heads are distributed into these three stages so we have more or less

consistent shedding but it isn't completely consistent we have a bit more hair in spring

so more hairs are in the anagen stage and we shed a bit more hair in autumn so more

hairs are in the telogen stage which is when they can fall out

it's like a weak version of how animals will shed their winter coats all at once but for

some people this difference can lead to noticeable shedding at different times of the year

this study took place between April 2010 and June 2011 in the northern hemisphere so if

you had a few more people starting their 6 months around June 2010 than over here or

over here then you would see an increase in the average hair count even if the treatment

wasn't having any effect

and if you look at the hair counts in other studies for the placebo treatment which is

where they have no active ingredients you can sometimes see similar or bigger fluctuations

in this study you can see that the placebo group goes from an average of 132 to 191 hairs

which is an increase of 45%

if we look at what happened in this study with minoxidil 2% at 6 months it actually

gave an increase in terminal hair count of 123% which is a lot more impressive than 5%

and as well as seasonal variation there are a whole bunch of other things that could be

impacting hair growth

it could be the fact they're massaging the scalp twice a day it could be something else

in the lotion having an effect

the details of the lotion aren't given in the paper

and these fluctuations could also explain why so many people on social media claim that

rosemary oil worked for them

one thing that we haven't talked about yet is that sudden hair loss often happens because

of a specific stressful event for example if you've been really sick or if you've been

really stressed and honestly that kind of covers all of us over the last few years

this sudden hair loss is called telogen effluvium and it's common with covid as well as things

like sudden weight loss or surgery and after the stressful event stops your hair will gradually

grow back

but usually it's when your hair is at its worst that is when you're going to be looking

at remedies and trying out things that you see promoted on social media like rosemary

oil

and so you'll see your hair grow back right after you've tried them and you'll think it's

the treatment working even if it was going to grow back all along anyway

this effect is called regression to the mean and I talk about this more in my video on

why anecdotal evidence isn't really reliable

there's also the issue of perception a lot of things do impact whether we think something

works and this can actually be seen in some hair loss studies

in some studies as well as looking at hair count they also asked the subjects whether

they felt like their hair loss improved

so for example in this study you can see that a lot of people felt like the hair loss was

worse after 16 weeks of using 5% minoxidil even though according to the photographs none

of them were worse

and in this rosemary oil study the self assessments do seem maybe a bit too good to be true

at 3 and 6 months all of the people using rosemary oil said that the hair loss had decreased

none of them said no change or that it got worse

for 2% minoxidil of the people said that hair loss decreased at 6 months and only seven

people said there was no change or it got worse at 3 months

now if you look at other studies even in studies that use 5% minoxidil you'll see people saying

that there was no change even with much bigger average changes in hair count

so it just seems like there's something very weird going on in this rosemary oil study

and as you'd expect for a treatment that probably doesn't have that much of an effect as well

as people on social media saying rosemary oil worked for them there are also heaps of

people saying rosemary oil actually made their hair loss worse

so what does this study actually tell us I don't think it really tells us much at all

the most generous thing we could say in my opinion is that

in a study that has really sus numbers where a low concentration of minoxidil unsurprisingly

didn't do very much rosemary oil also didn't do much

and this shows us another problem with the scientific literature

peer-reviewed articles cite other peer-reviewed articles and a lot of the time they don't

actually look very closely at them

this rosemary oil paper has been cited 93 times and just to give an indication of the

problem and how so much crap gets through peer review here are just the first eight

articles that cited this paper I got off Google Scholar

only one of them even indicates any sort of skepticism about the study

there are a few other studies with rosemary oil but they mostly use mixtures where rosemary

oil is just one of the components so it doesn't really tell us much about rosemary oil specifically

but even if that wasn't an issue the studies themselves aren't super convincing either

okay so if the only clinical study showing that rosemary oil works for hair loss is pretty

unconvincing what are we left with

well the intro and the discussion do mention why they wanted to look at rosemary oil in

the first place

it could potentially work in ways that are thought to improve hair loss in other words

it has potentially beneficial mechanisms of action

it could potentially increase blood flow to hair follicles and it's also an antioxidant

which could neutralize reactive free radicals which could be theoretically contributing

to hair loss

but the problem with relying on this sort of mechanistic logic is that there are a lot

of mechanisms happening inside your body and they can have completely opposite effects

so you can usually come up with mechanistic reasons why a particular ingredient could

cause both good and bad outcomes

it's a lot like trying to work out whether your friend Brian is going to be early or

late to lunch today

you can come up with lots of reasons why he might be early

he doesn't live very far away

he likes to wake up early

he has a car and he's a good driver

he is usually a pretty hungry dude

you can probably also come up with lots of reasons why he might be late

he has a busy job

it's hard to get parking near the cafe

it's raining there's a bit of traffic

and yeah some of these reasons are more convincing than others sometimes these reasons could

be so convincing that you pretty much know

like if Brian posted an Instagram Story 2 minutes ago of his flat tyre

but most of the time these reasons are nowhere near as useful as looking at past examples

of the same outcome

in other words is Brian usually early or late when you meet up?

and the closer the past examples are to your current situation the better your guess will

be

is he usually early or late when you've met up at this specific cafe for lunch before

when it's raining and there's a bit of traffic?

and that's why clinical trials which is where the treatment gets tested on actual people

and the outcomes get measured

that's why they are so useful they give us a gauge on what happens when all of these

competing mechanistic reasons add up which ones outweigh the other ones

my PhD was in medicinal chemistry which is the start of the drug discovery pipeline

we would usually start with really promising ingredients which are called lead compounds

with good mechanistic and in vitro evidence

those would go through more testing and hopefully they would turn out to be useful drugs

and even with really good mechanistic evidence one in 10,000 of these compounds that we tried

would work well enough in humans to end up as a successful drug

and the main reason that different compounds would fail was usually lack of clinical efficacy

in other words we know from experience that things with promising mechanisms don't necessarily

work well in actual people

and these drug candidates we were looking at would usually have a way higher level of

mechanistic evidence and convincing animal data which rosemary oil just doesn't have

and that's why properly approved drugs like minoxidil should really be your first point

of call

to get approved as a drug it doesn't just have mechanistic evidence it actually worked

in clinical trials too

I've come across some people saying that rosemary oil can block the enzyme that converts testosterone

to DHT which causes some types of hair loss it's called 5-alpha reductase

and this is really promising because it's how the hair loss drug finasteride works

this is the only study but there are a bunch of problems because everything about rosemary

just seems to be problems

the way the researchers made this rosemary extract that they tested means that it has

very different components from rosemary essential oil which is what everyone on social media

is talking about

the essential oil has mostly stuff that evaporates easily but this procedure means that you get

a whole bunch of stuff that doesn't evaporate and the substance that they think is the active

also isn't found in essential oil

but say you decide you want to make your own rosemary extract using their procedure then

now the problem is they needed 2,000 times more rosemary extract to get the same effect

as finasteride in their enzyme test which just has the enzyme swimming in a test tube

1 mL of 0.25% finasteride is usually used as a scalp treatment per day so if this was

getting into the scalp as well as a really optimized solution of finasteride you would

need almost 5 grams on your scalp and that's about a teaspoon

in the experiment they dissolved 2 mg in 100 microlitres of alcohol which converts to about

a cup of liquid

everyone is struggling to get a 1/4 teaspoon of sunscreen on their face so good luck with

getting 200 times that onto your scalp

they also tested that specific compound and you needed a lot less of that to have the

effect

you only needed two 230 times as much compared to finasteride to get 2/3 of the effect

but the concentration of this in rosemary is really low so to get that 2/3 of the effect

compared to finasteride assuming it gets into the scalp as easily you would have to use

up 2 kg of rosemary leaves every day

so after all of that is rosemary oil worth trying

in my opinion no

for me the lack of clinical trials besides this one puts it back at the bottom of the

heap

there isn't much to support it apart from mechanistic reasons which just don't really

give it a great chance of working and the level of this mechanistic evidence is really

not that high either

there's also the fact that it's a natural product so the levels of any potential active

ingredients in rosemary oil they're going to vary a lot depending on on where it's grown

when it's grown how it's harvested how it's extracted and how it's stored

there are actually three main types of rosemary oil which are named based on what their major

components are

it looks like this study used the cineole version which they aren't really clear about

but even within cineole rosemary oils there is a whole bunch of variation

plus essential oils contain allergens and irritants and these could actually make hair

loss worse

so there are competing mechanisms that could counteract the potential benefits

rosemary has camphor carnosol and cineole for example which have been reported to be

irritating and allergenic for some people

and we can actually see hints of this in the study scalp itching and dandruff actually

increase for the rosemary oil group

scalp itching also increased for minoxidil but again thanks to other better quality clinical

trial evidence we know that any irritation that could lead to hair loss gets outweighed

by the hair growth mechanisms

we know that overall minoxidil doesn't lead to hair loss but we don't know this for rosemary

oil

a side note this study doesn't actually say how they collected this irritation data which

is another huge red flag because a study really shouldn't be missing the methodology for a

full page and a bit of their results

if you do end up trying rosemary oil please make sure that it is diluted

if this study used cineole rosemary oil they diluted it by about 162 times so that is one

drop of rosemary oil per 161 drops of carrier oil or one drop rosemary oil per 8 mL of carrier

oil

it's also worth remembering that hair loss treatments generally are better at helping

you keep your current hair and making it thicker it doesn't really help you regrow dead hair

so the longer you try out less proven remedies and delay using more proven treatments the

worse your outcomes will actually be

so things you should try instead for hair loss

it is best to talk to your doctor or dermatologist

sometimes hair loss is because of an underlying condition or deficiency or allergy and if

you go back and fix that then the hair loss will resolve

and depending on the type of hair loss you have there are often more proven treatments

like minoxidil

if you are going to try rosemary oil it is probably a good idea to try more proven methods

at the same time

sometimes there isn't a reliable solution but it is still a good idea to make sure there

isn't some more serious underlying condition that you're missing

if you want more videos on hair care science you can check out this playlist

if you want a deep dive on how we sometimes know ingredients work even when the evidence

isn't that great you can check out my video on whether retinol is a scam