you'll hear lots of people say you have to use sulfate free
shampoo to avoid damaging or stripping your hair
you'll also hear people say you have to use sulfates to get your hair clean
they are both wrong
almost everyone misunderstands this fundamental thing about shampoos and
I think it's why so many people can't find the right products
I'm Michelle of lab muffin beauty science chemistry PhD and cosmetic chemist and person
who usually talks more about skincare science but we are doing hair today
I've been paying more attention to hair science on the internet lately and there are
so many completely wrong explanations and strong opinions and just people yelling at each other
but because I love pain apparently I am going to talk about it
I'm starting with sulfate versus sulfate-free shampoos
I've talked about it a bit before but I'm going into more depth because I think if
we really dig into the chemistry of it a lot of things about hair start making more sense
but before we talk about sulfates we have to talk about the state of hair science
not just internet hair science but actual academic hair science
it is a mess
there are three big reasons I think there's so much confusion
reason one hair is really diverse so much more than skin
different hair just does not respond to hair care products the same way
skin care seems complex but when you break it down it's actually pretty straightforward
maybe also it seems that way to me because I've been talking about it for so long
with skin type there's oily and dry and in between
then you have concerns like fine lines pigmentation acne
it does take a while to understand your skin and find the right products for it
I have to plug my ebook because I keep forgetting to do that
it walks you through that process
but when it comes down to it ingredients tend to work pretty similarly for everyone
if you have a hundred people use glycerin on their skin you might have 60 people's
skin get more hydrated and improve 20 people's skin stays around the same
and the final 20 might get worse for some reason like the glycerin helped
some other ingredients penetrate and the skin got irritated or they have an allergy
there is still complexity but you wouldn't have like half the people's skin dry out more
but that's kind of how it is with hair
even just with the shape of the strands you have straight curly a million different levels
and types of curly kinky tight coils the coils might be rounder or flatter or a mix
and shape makes a massive difference to how hair responds to different products
variation in geometric shape is just not something we have to think about much with skin
take wet versus dry detangling for example
the way water interacts with hair is weird
I'm not going to go into too much detail
here because that's a whole topic for like five videos but in short
it weakens the bonds gluing the inside of the hair
together which is why hair gets stretchy when it's wet
but it adds stickiness to the outside of the hair so hairs stick together
more easily and you need to use more force to get the comb through
water also raises the cuticle scales
these are the roof tile looking cells on
the surface and that means they can bash against each other more and chip
so all of this means it's less damaging to to detangle hair when it's dry
but that's just for straight hair it is the opposite for curly hair
all of these effects still happen but changing just the shape of the hair strand
that is enough to change the physics of how the hair interacts with a comb
the cuticle scales still stand up more the curly hair is still
weaker on the inside and sticky on the outside the hair is still more fragile
but there are two big differences
first off the hairs stick to each other less because there is less
alignment or tessellation between curly hair strands compared to straight hair
it's like how when you cook spaghetti they stick together much more than with spiral pasta
on top of that the weakening of the bonds inside the hair actually makes the curls loosen in shape
a looser curl means that geometrically there's
less chance of tangling and causing damage and breakage
so the change in the physics of how that curl interacts with the comb
that can offset the damage from manipulating wet fragile hair and overall you get less breakage
there's a few studies showing this
but where is the line
is it better to detangle say wavy hair when it's wet or dry
what if you use a brush versus a comb or a different type of brush
what if you detangle it from the bottom up or just straight from the top
what happens if you partly dry the hair
those answers just
don't seem to exist
and we are just talking about water and hair shape
we're not even talking about other ingredients
how often you wash your hair
how much damage you have
the type of damage you have
if you bleach or straighten your hair
or how long your hair is or how oily it is
there are a lot of variables
and this kind of overlaps with reason two hair science is just really sparse
we just do not know that much about hair
I used to assume that hair was really straightforward
I mean hair is dead skin is alive
if you're doing tests on hair strands it should be really easy
you just buy a bunch of hair
that is so much easier than finding volunteers
but because of all this diversity with hair every experiment you do - you just
can't necessarily generalize this to other types of hair
on top of that there are tons of other variables that make a huge
difference to hair like what humidity the experiment started and ended up with
when I go places with high humidity it gets a little extra body okay
that alone can massively change the results and we all live in places with different humidities
and the humidity changes throughout the day it changes in different rooms
so it isn't like if every study did experiments at 20% humidity that would solve the problem
hair scientists don't even know the structure of hair in that much detail
the understanding is still evolving relatively quickly
and there just isn't that much consistency with terminology even in the peer-reviewed literature
so for example around the late 90s some hair scientists just decided half the
protein in hair wouldn't be called keratin anymore and they have good reasons for that
but not everyone got the memo or maybe some hair scientists just didn't agree
so you'll still read things like "hair is 80% keratin by mass" even in this paper from 2017
and this isn't a huge deal here because it is pretty clear they're using that old definition
but if a paper says "we concluded that this
ingredient works on keratin and hair" do they mean keratin or do they mean
keratin
[muffled screaming]
Reason 3 hair products aren't just about individual ingredients
the two main hair products shampoo and conditioner
the way they work isn't about the individual ingredients the
overall formulation is really important
and yeah we say that a lot about skincare but it is even more the case with hair care
and this is central to this debate about sulfates and shampoos
sulfates usually refers to sodium lauryl sulfate and sodium laureth sulfate
these are two of the cleaning ingredients or surfactants that
you find in things like shampoos and cleansers
surfactants are special because they have a head that likes water and a tail that likes oil
as you hopefully know from
Life
oil and water don't usually mix
so surfactacts can help oil break up and mingle
with water so you can rinse it away and end up with clean hair or skin
the tails are pretty similar in surfactants so most of the time we're talking about the heads
sulfates have sulfate head groups
chemists are not imaginative when it comes to naming
and yes if we compare sulfates on their own with other surfactants on their own
they have good cleaning ability but because it's hair science there is more complexity
these four diagrams show four different ways that shampoos clean at a microscopic level
each of these diagrams is read from left to right
the pink tadpoles are the surfactants and you can
see that the surfactants are coordinating to clean the hair
this is called a supramolecular process where the
molecules are interacting without going through a chemical reaction
it's a bit like molecular choreography
now this isn't like four separate processes
all four of these are probably happening on your hair at the same time to different extents
there are probably still more mechanisms still to be discovered
how much of these depends on the formula of the shampoo because the pink tadpole surfactants
won't all be the same they'll have different tendencies to interact in different ways
but it also depends on what sorts of stuff or soils you're cleaning off
because they are also part of this choreography
so for example if you have bigger blobs of oil on your hair then this one is probably happening more
because some of that oil breaks off multiple times instead of all of it coming off at once like here
but if you have big particles that don't break up easily then it might all just be figure 4
this one happens more at high surfactant concentrations and that is another variable
and that's not just about the concentration of the surfactants in the formula
at the start of the shampooing process you've just put the shampoo on your hair
it's at maximum concentration but if you add more water or you start rinsing then
the concentration will decrease and you might have less of this happening
and this is already getting pretty complicated but it's still a massive
oversimplification because hair science will not give us a break
if you look at the ingredients of almost any shampoo it'll have three or more difference
surfactants that means that these pink tadpoles in the diagram aren't all the same
if you change the ratio of the ingredients or swap
one of these out with something else then the shampoo might work quite differently
plus there's a bunch of other ingredients that aren't shown here like polymers and
oils and those will also interact with the surfactants and affect how it cleans
and on top of that things like the texture of the shampoo the opening of the bottle that's
going to change how much you dispense and how the shampoo spreads on hair
so in case you didn't notice it is really complex
and what that means is trying to predict what happens just by looking at whether
some of these pink tadpoles are sulfates or not - that is just not going to tell you much
it just isn't as simple as "it has sulfates
it'll clean better" or "it'll strip or degrease your hair"
if it was it would be so much easier for everyone to just find the right shampoo
same with the pH of shampoos I see lots of people saying you have to check the
pH and make sure it's acidic and again that is just not a
very meaningful piece of information when the whole thing is so complex
it's a bit like trying to predict how a food tastes from how yellow it is
and even if you knew the full formula of a shampoo every single ingredient what
concentration they're in where they got the ingredients it would still be pretty
much impossible to predict how it's going to interact with itself let alone with
different types of soils on your hair at different stages of the shampooing process
it takes a ridiculous amount of computational power to model
a much simpler sort of system with way less moving parts than a shampoo
this is why cosmetic formulators spend so much time just during trial and error making formulas
and trying them out changing little things about a formula can make a huge difference
here's one example
Good Housekeeping did this test with 10 shampoo
and conditioner pairings that were meant to protect colour
some of these had sulfates and some didn't
there were salon and drugstore brands
the set that stripped hair dye the least had sulfates
it's this tresemme set
they also have this article where hair scientists talk about how complex it is to formulate a
shampoo but even with their own results as proof and two scientists with PhDs explaining
to them that it's not about sulfates versus no sulfates their article on color stripping
and shampoos still has this BS about sulfates "sudding" the hair and causing pigment loss
these myths run deep
but I think a lot of us have had the experience where we try a sulfate free
shampoo and it does feel like it's gentle or it doesn't clean enough
the way you frame it probably depends on whether or not your hair likes that
and the reason for this I think is a sort of circular
reasoning that happens quite a bit with products
formulators know that people looking for sulfate free probably want something that
cleans less they know there's all these widespread myths about sulfates being
harsh they've been going around since the 90s like in this email forward
"SLS is used to scrub garage floors and it is very strong"
even if the formulator didn't know about all this because I don't know
if they've been hiding in a hole it's probably on the product brief
that's the description of the product that the formulator works off it's
usually written by marketing people based on consumer research it'll have
the marketing claims that they plan to put on the products so chances
are the brief says "sulfate free" as well as "gentle" and "not stripping"
so there's a good chance that if you grab a random shampoo with sulfates
and a random shampoo without sulfates the one with sulfates will clean better
it's not because just adding sulfates automatically makes a shampoo strip more
we saw that it can be formulated to strip colour the least
it's just because of intentional product design
the formulator formulated with sulfates and to make it clean more
they might have also changed some of the other
ingredients to make it feel like your hair is cleaner
but brands don't all have the same idea of what counts as gentle and some brands
choose not to follow this consumer trend so there's going to be lots of exceptions
it's like how if you grab a shampoo in a black and green bottle there's a pretty
good chance it'll smell minty because product designers have decided that is what men like
this is exactly the same situation with foam and cleansers
how well a product foams doesn't tell you about how well it cleans
what's happening on a molecular level is different
how well something first depends on how well it
interacts with air how well it traps air in a thin film
cleaning is about how well it interacts with oil and dirt
both cleaning and foam rely on surfactants but apart from that there's no real correlation
between which surfactants foam best and which ones clean best
and there's so much that depends on the overall formula there are lots of
other ingredients that help to create a nice foam
again both are complicated supramolecular processes there are so many moving parts
but if something doesn't foam when we use it we tend to feel like it's
not cleaning properly it's a purely psychological thing and I personally
still have this gut feeling even though I know all of this chemistry behind it
humans did not evolve to be perfectly rational in our feelings
so formulators make sure that shampoos and other
cleaning products usually foam really nicely for us
but if we don't see it then it doesn't have to foam to convince us
one example is detergents for dishwashers they're actually kind of formulated the opposite way
they have to clean really well with as little foam as possible because foam causes pressure
and if that builds up then it can make the dishwasher leak and flood our kitchen
sploosh
bottom line sulfate free sulfate containing doesn't really mean much
how well a shampoo cleans is way too complicated to predict that easily
it's much more useful to actually look at what the shampoo is trying to tell you
if it says clarifying then it's a shampoo designed
to clean your hair better doesn't matter if it has sulfates or not
if it says colour protection it can have sulfates
and still strip dye less than a sulfate-free shampoo
if you stick to these rules about sulfate versus sulfate free then
you would have missed out on the least colour stripping shampoo
it's also really useful to look at reviews
from people with similar hair to you and try it out on your hair
let me know what you thought of this deep dive into hair science what I should talk about next
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