Merino wool clothing benefits sleep and skin health through thermoregulation (i.e. body temperature control). The immune system is improved as a byproduct of wearing wool and specific studies are cited in this article.
Thermoregulation is part breathability, part moisture wicking and part body temperature modulation. How these functions are distinctly different in Merino than cotton and polyester are explained below.
Since we’re talking about Merino wool clothing and health, I have to ask about the current threat, the COVID-19 virus. Does Merino clothing provide protection from environmental threats such as illness-causing bacteria and viruses?
We've had a huge number requests and interests to understand the antibacterial and antiviral aspects of wool. But, right now the protection really comes from wool's effect of improving sleep and not from some kind of virus resistance of the fabric as a physical barrier.
It's known that if you sleep better your immune system is strengthened. The difference between six hours and seven hours sleep a night is massive. The people who only get six hours are four times more vulnerable to viruses. So Merino, and all types of wool, contribute to a good night's sleep. The sleep factor is something most customers don't know about, but it is another aspect of improved wellness attributed to wool.
The general market isn't so aware of the health attributes of clothing, but specific parts of the market are. Firefighters, military and other first responders are becoming increasingly aware that their clothing affects their health. The active outdoor group is another group that understands this too. We hear from rock climbers, for example.
They're halfway up the cliff and the wind is blowing. If they're wearing a cotton t-shirt at that stage, they're freezing. They've worked hard to get up there and the wind's blowing and it's just icy cold. But, if they're wearing wool, it's breathing and taking moisture away from the body, so there is no moisture to freeze. That makes a huge difference to their energy levels and comfort. So, certain segments of the market are pretty sensitive to this attribute of Merino and health, but not all.
The big difference is that wool fiber is hydrophobic meaning it doesn't like having moisture on the surface of the fiber. It repels water on the outside. But inside, the fiber absorbs moisture vapor. In other words, it will absorb and release moisture vapor very effectively, but not liquid moisture. It's sort of repels liquid moisture. For example, if you're running for the bus and you're in the early stages of the body wanting to sweat, before it actually sweats, the body first emits moisture vapor. That vapor gets absorbed by the wool fiber. The fiber grabs it off the skin then conveys it to the outside of the garment and releases it to the macro environment. It's constantly sucking moisture vapor away from the body and releasing it. So, it defers the onset of sweating because it's cool as it's releasing it. The process of releasing actually has a cooling effect on the body of the wearer.
If you're wearing a cotton t-shirt in the same scenario, running for the bus, it's hydrophilic. The opposite of hydrophobic. The cotton soaks up moisture like a sponge, but it doesn't move vapor effectively like wool does. So, it lets you sweat as you're running for the bus, soaks it up like a sponge and remains wet. This is why cotton clothing can decrease the wearers core body temperature when the ambient temperature drops for any reason. The sun goes down or the wind blows. But, if you're wearing a Merino wool shirt your skin is dry, or drier comparatively. Ideally, it has removed the onset of sweating by moving the moisture vapor away from the skin fast enough. But, that doesn't happen if the body sweats faster than the wool can act.
But, even if the wool shirt is soaking wet it doesn’t freeze like cotton. How does that work?
Merino clothing is exothermic. In other words, the action of absorbing moisture generates heat. Contributing to that is what was mentioned before about wool being hydrophobic. Since it doesn't have moisture on the outside, it doesn't feel clammy and cold. It doesn't feel wet because it's not like a sponge. Not only does it defer the sweating, but when you do the sweat doesn't accumulate on the surface of the garment. It's not wet and soggy because it's hydrophobic. So, that's the key difference and it's quite noticeable.
Polyester doesn't absorb moisture vapor, but it can be made hydrophobic or hydrophilic depending on how the manufacturing process is undertaken. Normally, it starts off hydrophobic, but it can be manufactured in such a way, and finishes applied, to make hydrophilic. But, since it doesn't absorb vapor it's not deferring sweating. You'll sweat just as readily in polyester, and maybe even more so, as in cotton. And, of course, once it's been worn it generally absorbs the body odor as well. I'm a regular cyclist and if I wear my polyester I can almost smell myself before I get down to the end of the driveway. But when I wear my Merino wool gear, it absorbs and locks away odors within the fiber and releases them in the wash. I suppose polyester is somewhere between Merino and cotton for the rock climbers. They can certainly distinguish the differences in performance and comfort when they're halfway up the rock face. Wool and cotton are probably at the extremes and polyester somewhere in the middle. But, if they're doing three days of rock climbing, they're going to notice that body odor at some point and it won't go away in polyester.
The process of taking the moisture off the skin and releasing it to the atmosphere through evaporation is actually a cooling function. That's why the body sweats: to evaporate. And as it evaporates, it cools. Essentially, wool is helping the natural function of the body. The body is trying to sweat and then have evaporation. Wool lets it work.
When I read about how Merino wool keeps you warm and how they keep you cool, the explanations of the two processes seem very similar. Can you make a clear distinction between the two?
I understand the seeming contradiction. The process of wool absorbing moisture off the skin is exothermic. Meaning it gives off heat. That would indicate that if you're sweating it's making you hotter. But, it then releases that moisture to the atmosphere and that evaporative process is a cooling process. One is helping the other to some degree. But, the way I much prefer to think about it is that wool is making a more stable microclimate. It's not exposing the body to sudden changes one way or the other. We can tolerate reasonable cold and we can tolerate quite a lot of heat. But, what humans can't tolerate is a sudden switch from one to the other and that's where wool has its benefit. It smooths out the temperature so that the body has time to adjust and acclimatize to this new circumstance. It takes the peaks and troughs out of the climate letting the body adjust more slowly. And that's what I think the rock climbers perceive; they don't get sudden shifts in body temperature.
So when you say that the body cannot tolerate sudden temperature changes, do you mean that's when the immune system weakens and energy levels go down?
Yes. Humans can exist at the equator down to the southern parts of the planet all the way up to the northern parts. They can tolerate it all. But, they don't like a quick shift from one temperature to the other. It's this buffering action of wool that really prevents that from happening. It's this feature that is appreciated by the aforementioned rock climbers.
I haven't seen studies on it, to be frank. But, we have seen firefighters use it in a layered system. They have to wear their heavy duty fire resistant outer layer. In active circumstances, fighting fire, they're like a swimming pool on the inside. They're sweating and there's nowhere for the sweat to go. What a Merino wool base layer does for them is it takes it away from the skin and gets it to another layer a bit more remote from the body.
It's a bit more comfortable because it's not on you. It's somewhere else in the layers. It's a good question and I don't have a particularly good answer because it's not being studied. It's an area that needs to be explored more to fully understand. But, the fact that we get this positive feedback, especially from first responders, they put themselves in these hazardous circumstances and they try the Merino base layer with the impervious outer layers and say this is the most comfortable arrangement that they've been able to find. That's why they continue to use Merino. It's a lot more expensive than a cotton t-shirt or polyester t-shirt, but they go back to the Merino base layer nevertheless.
What is the impervious outer layer you mentioned?
So they're wearing wool underneath Kevlar and the wool is basically used to keep their body dry.
Yes, to the degree it can in that circumstance. It has a finite ability, but it will move the moisture away to a mid layer or somewhere between the base layer and the Kevlar.
Merino clothing brands advertise that wool’s odor free characteristic is due to wool being antibacterial and/or antimicrobial. However, I've heard wool experts say that it is neither. Can you explain?
There are two features of wool and you mentioned one of them. Because it's managing the microclimate between skin and the garment and preventing it from becoming moist, the bacteria don't thrive. They don't reproduce so much in that drier microclimate as if you were wearing cotton or polyester, so the population of bacteria is less. Sweat doesn't smell, but bacteria that get access to sweat and reproduce cause the odors. So, in the sense that it reduces, or limits, the reproduction of bacteria it's sort of antibacterial. That's the first point.
The second point is that on the surface of the fiber, after the lanolin is removed during processing, and there's very little lanolin remaining on a wool garment it's almost entirely removed during processing, but there is a layer of lipid on the surface of the fiber that has the same features as some antibacterial products. But, we don't know enough about that to claim that it is actually antibacterial. And it's not a claim that we put on our website, or that we actively promote that wool is antibacterial. And one reason for that is that at the end of its life, in the right environment, in a moist environment, it biodegrades quite rapidly. And, it's a lot of bacteria that are consuming the wool at that stage. We can't have it both ways. We can't say it's antibacterial during its life and then say it's gobbled up by bacteria at the end of its life. Again, it's only if the wool is in a moist warm environment that it biodegrades rapidly. By contrast, there's wool that was found in the pyramids. 5,000 years old and it was still in quite good condition because it was in a dry, cool place. We say wool limits the reproduction of odor causing bacteria. That's about as far as we go.
Absorption of volatile organic compounds (VOC’s) is another version of odor resistance you don't hear much about. That actually that applies to woolen carpets and textiles, where you've got this sick building syndrome. Some buildings release a lot of formaldehyde and other VOC's from timber and walls. If you have wall textiles, wool curtains and wool carpets, they absorb those VOC's and lock them away. So, all of those attributes were being well accounted for in the 1900's.
It's the same feature of managing the microclimate. Eczema is a good example. Eczema sufferers have very dry skin that releases moisture far too freely. The moisture leaves their skin; then the skin cracks; and then bacteria inhabit the cracks and cause all the redness, itchiness and pain that is eczema. But, because wool is managing the microclimate, it's not just moving moisture away from the skin and out into the environment. It's also pulling moisture back from the environment into the microclimate and buffers the relative humidity and temperature in that microclimate. So, for eczema sufferers, it's actually working the other way around than the earlier example of running for the bus and pulling moisture vapor off the skin. In this case, it's pulling moisture inside and keeping their skin a bit moister. Merino clothing smooths out the change in temperature and relative humidity. It doesn't expose you to sudden changes because it's constantly buffering by moving moisture one way or the other. The body doesn't like is sudden changes in terms of thermal regulation. It likes to stay even and balanced, and that's what wool does. It smooths out the temperature and the humidity by pulling it one way or the other through the fabric. If there's more moisture on the outside, it pulls it inside. Conversely, if there's more moisture inside, it'll push excess moisture out. That's how wool helps the body thermoregulate.
This graph on the "Moisture Vapour Absorption" slide [below] tries to show what we were discussing before about Merino's ability to absorb and release moisture vapor. It's twice as good as cotton in this respect and it's about three times as good as polyester. The way it works in the running for the bus example is if the skin is generating a lot of moisture vapor, the wool is pulling it out and releasing it to the atmosphere. But, if you're an eczema sufferer and you've got dry skin, wool garment will pull is it the other direction. By constantly seeking balance, it buffers the temperature and relative humidity in the space between the skin and the fabric.
Your research revealed that the health benefits of wearing Merino clothing differ by age group. Can you explain?
The science is showing that everybody, at all life stages, benefits from wearing Merino wool. But, when it comes to those areas of sleep health and skin health, the people on the edge of the distribution benefit more than the people in the middle. In other words, if you're somewhere between 15 and 30 and you're fit and healthy and eat well, you won't notice wool's benefits unless you put yourself in an extreme circumstance. Or, you have some condition that pushes you into an extreme circumstance.
On sleep health, we found that people over about 50, if they're sleeping in Merino wool, they benefit quite noticeably from wool. They are often sleep challenged; have poorer thermoregulation than younger people; have a diminished sweating capacity; and sort of can't cool themselves as effectively. That age group is more vulnerable to heat stress and they wake up easily. So, we wanted to see what wool does for this age group.
To see this level of sleep improvement, is there a recommended quantity of wool? The weight, or fiber composition of the bedding?
Our research has shown that the most important thing is to choose the right quantity, thickness of duvet for example, for the circumstance you're in. You'll probably have a Winter duvet and a Summer duvet. If you're in a certain climate, you might need a Spring duvet because if you overheat under wool you're not going to have a good sleep. It does have to be matched to the environment you're in.
This study here on sleep health, actually did just look at clothing and nothing else. These 36 adults you see referred to here, they either slept in Merino wool pajamas, cotton pajamas, or polyester pajamas.
They had no sheets, no blankets, no nothing. So we didn't want the study confounded by other layers of bedding. We got them to sleep in sleepwear only. They were then wired up to polysomnography equipment to look at how deeply they slept, how long they slept, how many waking instances they experienced and how quickly they fell asleep. Basically, all of the metrics that we measured were better in wool. Not all of them were statistically significantly better, but everything was better for the group in wool pajamas. The statistically significant component was that they had less fragmented sleep in Merino wool than cotton or polyester. 12% less fragmented, for example, than polyester. So, that means that they either woke up less often, or they came out of deep sleep, into light sleep, less often in wool. They also had faster sleep onset. This was particularly so for the over 65 group. They fell asleep in 12 minutes on average versus 27 minutes on average for the cotton wearing group. The consumer has to weigh up the worth of those extra 15 minutes staring at the ceiling. But, we thought it was a reasonably meaningful extra amount of sleep time.
Another point is that there are more benefits at the extremes, When we looked at the people who benefited most of among the people aged 50 to 70,
it was the older people; the ones with a higher body mass index; and the ones who were inherently a poorer sleepers. So, it goes back to the same thing that if you're on the edge of the distribution, you're more likely to benefit from wool in a statistically significant way.
And increasingly, when I say Western you might think of Europe and America and Australia, for example. But, Western is now Hong Kong and China. They're all switching over to Western lifestyles. Unfortunately, this is causing people to become allergic to the planet. The remote you are from the land, from animals and from the way humans used to interact with the planet, the more likely you are to find yourself allergic to the planet.
Something about urban lifestyles and city life is causing skin problems in children?
Yes. And not just skin problems, but a whole series of allergy problems. The dermatologists that I deal with, see children with red skin and ask the mothers, 'Was your child born via Cesarian section or naturally? Was your child raised in the country on a farm or in the city?' On a farm they get exposed to nature. 'Did you have pets when your child was young or were you pet free?' Pets spread their bugs around quite effectively. They ask these questions to see just how far removed from stone-age humans your child is.
The further we get away from that, the more likely you are to be allergic to the planet when you're exposed to those things that you didn't grow up with. With eczema sufferers, it's the 0-5 year old age group that are most at risk. Cesarean section birth, for example, is an increase in risk because they don't get exposed to everything that happens at the bottom end of the body during birth. They get covered in a lot of stuff down there that starts their introduction to the planet.
This study at Murdoch's Children's Research Institute had 40 kids age from 0 to 3 years. And they compared cotton clothing to super fine Merino wool base layer.
The study is a crossover design where half of the 40 kids wore cotton for six weeks, and then wool for six weeks. Their eczema symptoms were monitored during the transition from one fiber to the other. The other half started off with wool and then changed to cotton. The reverse from the first group. They called the second group wool first and the other group cotton first.
If you look at the cotton first group [below], you can see that during the first six weeks their eczema symptoms initially got a bit better. But then, it bounced back up again. When they changed to Merino wool, their symptoms dropped quite suddenly in weeks 9 and 12. The wool first group, once they started wearing wool, their symptoms dropped consistently. When they changed to cotton, their symptoms returned to pretty much where they started. This crossover design is what the scientists like most, because they can sort of turn on or off the treatment and see what effect it has.
We're talking about babies with soft skin wearing Merino wool, but many people still think wool is itchy because. The fact that you can wear a Merino wool shirt that is not itchy is a big surprise to them. But, it goes far beyond wearing Merino comfortably because the softness of wool is actually considered therapeutic to the skin rather than an irritant to be tolerated.
Can you comment on the changing perception of superfine Merino wool’s comfort?
You're exactly right. The perception of itchiness a huge barrier. Especially in the US because people think that they are allergic to wool because they put on some scratchy old jumper and it caused a flare up in their eczema symptoms. They say that wool is an allergen and I'm allergic to it, so I would never be involved in a study like this. It's actually quite a barrier for us to get these studies done in the US. But once they start, they rapidly realize that if you have a 17.5 micron Merino wool base layer it's very comfortable and they don't have that problem. They still have a perception that wool is hot and it's only to be worn in winter. So, we have a study underway right now in Chicago and some of the mothers are saying, 'Well, we can't have the baby in wool over June, July & August, because it's too hot. They'll overheat.' So, we tell them that it's a 150 gsm Merino wool base layer product. Have a go and try it out. And gradually, you start to break down some of these perceptions. But, it's a massive problem. Especially the eczema market because they still have this old fashioned idea that wool is scratchy, itchy and a potential cause of allergies.
So, even 17.5 microns on a baby’s skin is comfortable? Their skin is so soft and sensitive.
No problem at all. In the pilot trial that led up to this we explored other microns. Around the 19.0 micron mark is where we started to get feedback that it wasn’t appropriate. But again, at 17.5 microns there were no indications of irritation or itchiness at all.
The next area on our radar is cognitive health. We want to test circumstances such as people under stress. For example, if a pilot is landing the plane in extreme weather and everything's going wrong, does he think better if he's wearing a Merino wool base layer compared to other fiber types because his body is thermoregulating better and he's cooler and calmer? Does he make better decisions in that circumstance? The same goes for the general thinking about sending the troops over the hill to fight the enemy. Does he make a better decision if he's wearing Merino wool as opposed to other other fiber types? But, we haven't commenced that area of research yet.
There are more growers in Australia responding to market pressure by increasing the supply of super fine Merino wool by changing the genetics in their animals to go finer and finer. There's not much point going finer than about 17.5 micron. Some growers go down as far as 11 microns, but after 17.5, it's just so comfortable anyway, it just feels like it's some other material. So, they're doing that by purchasing their Merino rams from a different supplier that can provide super fine wool. And the genetics are much better now. Back in 1980, if you wanted super fine wool, you might only cut two kilos from each animal. But nowadays, they're cutting five to seven kilos off animals and still getting super fine wool. So, it's much more profitable.