Brushing wet hair- is it good or bad?

A discussion has lately sparked in several groups on Facebook regarding the potential damage that can occur to the coat when we brush in wet hair.
There have been lots of opinions, some of them making their way out to the general Facebook feed.
That has resulted in posts ridiculing the side that says that brushing does cause damage. No scientific evidence for the No damage claims has been provided, just a loud voice in capital letters, cheered on by the fan club.
When science that proves that it does cause damage is presented, the post is removed so that the fan club can’t see it and they still believe the original claim.

This annoyed me a bit ( yeah – I know… I am sad 🤣🤣), so I resort to what I usually do when science is ignored…… I make a blog post 😊.

One of my science educator friends, Christien Pearson, did a long post on her Facebook wall about it –  and you can find lots of links to the science there.

Just click on “See more” in her post below and you will see her whole text without having to go to Facebook.

But I thought I share some more science on the topic to make it easier to understand WHY it happens.

So let us start the journey into the microscopic world of a dog’s hair shaft.

 A canine hair is composed of three main parts: the cuticle, cortex, and medulla. The cuticle is the outermost layer, the cortex is the middle layer, and the medulla is the innermost layer.

The Cortex

The cortex is the thickest and most important layer of the hair shaft. It constitutes about 90% of the hair’s weight and provides it with strength and elasticity. The cortex contains keratin, a fibrous protein that gives the hair its colour, texture, and shape. For example, curly hair has a more twisted and irregular arrangement of keratin than straight hair, which is more linear and uniform.
The keratin fibres act like the strands in a hemp rope, it’s the sheer amount of them that gives the hair its strength.

The cortex also contains pigment granules called melanin, which give the hair its colour. The melanin granules are produced by specialized cells in the hair follicle called melanocytes and are transported to the cortex as the hair grows.

The Medulla

 The medulla is the innermost layer of the hair shaft and is not always present in all hairs. The medulla’s function is not well understood, but a theory is that it helps to increase the hairs insulating properties. The medulla is typically present in thicker hair types, such as guard hairs, and is absent in finer hair types, such as undercoat hairs.
The medulla has different shapes in different breeds.

The hair shaft’s diameter and shape vary depending on the breed and location of the dog’s body. For example, guard hairs on the neck, shoulder and croup area in most breeds are thicker and longer to act as protection.

The damage we can cause

 The cuticle is the outermost layer of the hair shaft and serves as a protective barrier against physical, chemical, and environmental damage. Anything we do in the salon, such as washing, brushing, drying, and de-matting can cause damage to the cuticle, leading to hair breakage, split ends, and dullness.  But its not only that, everyday events as being out in the sun or being petted causes some damage.
It’s therefore important that we know what can happen so that we can adapt our way of working to prevent/reduce the damage.

What I am listing here is based on reports in scientific literature. Hair damage is well researched,so if you want to learn more , go to Google Schoolar and type in Hair damage and you will be occupied for a loooooong time reading all research articles.

And someone might argue that this is research done on human hair, but lets not forget that dogs are not special mythical creatures. Hair structure is the same regardless if its on a human,sheep or cow.

“Normal grooming of hair, including combing, brushing, and shampooing, also produces damage that is progressive. This phenomenon is described in detail by Garcia et al. “.

The Effects of Washing

Washing can cause mechanical and chemical damage to the cuticle. The mechanical damage is caused by rubbing, scrubbing, and twisting of the hair during washing. ( we have all encountered the dogs that gets matted during the wash )
It can lead to cuticle lifting, breakage, and roughness, which results in matting and dullness.

Chemical damage can be caused by the use of highly alkaline shampoos, which can alter the cuticle’s pH and disrupt the hydrogen bonds that hold the cuticle cells together. A lower pH will seal the cuticles allowing for a smoother hair and less damage.
This damage can lead to cuticle swelling, lifting, and cracking, resulting in hair breakage and split ends. The use of hot water during washing can also cause cuticle swelling and damage.

” Therefore, both FESEM and TEM images, showed that the washings cause mechanical damages on the hair strands, removing cuticle cells and leaving some residual cuticle materials on the surface.”

Richena, M., & Rezende, C. A. (2016). Morphological degradation of human hair cuticle due to simulated sunlight irradiation and washing. Journal of Photochemistry and Photobiology B: Biology, 161, 430–440. doi:10.1016/j.jphotobiol.2016.06.002

When wet, hair can be stretched by 30% of its original length without damage; however, irreversible changes occur when hair is stretched between 30 and 70%. Stretching to 80% causes fracture (Dawber and Messenger, 1997).

Water absorption causes hair shaft swelling. And when soaked in water hair weight increases by 12–18%.

Towel drying is also something that has been found to cause damage, the rubbing action causes friction to the cuticles and can damage them. Hence why its important to avoid that if you have a longer coat. The rubbing will also cause the hairs to tangle up and cause matting.

“Water causes hydrolysis, that is, temporarily breaks the hydrogen bonds and makes the molecule malleable and consequently, fragile to the hair strand due to lowering in elasticity and increase in plasticity, which means that the wet hair, if deformed, does not regain its original shape. When that hair is wet, the cuticle scales lift, leading to increased cuticle removal, cuticle fragmentation, and cracks to the fiber axis”
Int J Trichology. 2014 Jul-Sep; 6(3): 95–99.
doi: 10.4103/0974-7753.139078

The effects of brushing/combing in wet hair

Brushing can cause mechanical damage to the cuticle, particularly when done vigorously or on wet hair. It can lead to cuticle lifting, breakage, and roughness, which can result in matting, and dullness.

Broken cuticle scales that is standing straight out will act like a velcro band,causing the hairs to stick to each other. When you pull them apart,the scales will be even more damaged.
The second part shows the over strecht fibres that eventually break,just like the fibres in an elastic band that time after time gets overstreched.

When hair is wet, it swells and stretches, which makes it more elastic and easier to manipulate. This is due to the hydrogen bonds between the keratine molecues being disrupted by the water.
However, this also means that the hair cuticle is lifted, which makes it more vulnerable to damage from external forces such as brushing.. The bristles of the brush can catch on the lifted cuticle, leading to tangling and further damage. This is especially true if the brush has sharp or rough bristles that can scrape or scratch the hair shaft.

The loosened hydrogen bonds also means that the hair is weaker and therefor more prone to breakage especially if its stretched.
When we stretch it beyond its capacity, small fractures occur inside the hair shaft and they will eventually lead to a detachment of the cortex from the cuticle and in the end cause the hair to break.

Here are a few snippets from scientific literature about the damage that can occur :

“straining hair at humidity < 65%, corresponding to the humidity regime inside the microscope chamber, causes fracture at the CMC between cuticle layers due to weak bonds between hydrophobic components, particularly between the side chains of the fatty acid 18-methyleicosanic acid and the contiguous fibrous protein layer. This initial partial fracture of the cuticle is manifested as the initial decrease in elastic modulus. The generalized internal void formation eventually leads to detachment of the cuticle from the cortex”
Camacho-Bragado, G. A., Balooch, G., Dixon-Parks, F., Porter, C., & Bryant, H. (2015). Understanding breakage in curly hair. British Journal of Dermatology, 173, 10–16. doi:10.1111/bjd.13241

“Wet hair has higher combing friction than dry hair. Combing wet hair is more likely to stretch brittle hair to its breaking point “(Draelos, 2005).

“It has been shown that wet straight hair possesses higher combing friction than dry straight hair. This is an interesting observation, leading to the idea that hair should not be combed when wet to avoid stretching the hair shaft to the brittle breaking point.“
Hair Care: An Illustrated Dermatologic Handbook By Zoe Diana Draelos

“Observations made during this study have indicated that wet hair is far more susceptible to damage during grooming than dry hair, and it would thus appear that minimal handling and brushing of wet hair could reduce the extent of physical damage to the hair”
A study of damaged hair VNE Robinson – J Soc Cosmet Chem, 1976


Christein posts lots of links in her Facebook post as well.

A lot of the science literature mentions that by using conditioner when we handle wet hair, we can prevent a lot of the surface damage as the conditioner will seal the cuticle scales. But it’s still important to avoid to brush in the soaking wet hair as it will force it to stretch.
Allow the hair to dry without the brushing and start to brush when its semi dry instead. This will also speed up your dematting as wet hair will cling together,delaying the separation of the mat.

My take away message

Science is very clear, wet hair is more easily damaged when you brush it as it’s easy to overstretch it and cause breakage. The risk is also high that you do damage to the cuticle as the scales are swollen due to the water and that causes them to rise and you catch them with the brush and damage them. The swollen cuticle is also at risk of breaking up due to stretching and bending.

But ……..Any person that has been dealing with a show coat knows the mantra – Never brush in a dry coat…. as that causes damage to the hair due to the friction and it will eventually break.

We also never brush in a dirty coat as that also causes damage as we rip the cuticle scales apart. The scales on a dirty coat look like Velcro and when you rip the hairs apart, you rip up the scales even more.
A clean well conditioned hair is less prone to damage according to scientific literature and show people also know that from experience.

What we have to remember in this discussion is the terminology. When we talk about wet hair -it’s hair that is soaked in water.
A dog coming from the tub and just towel dried. Not hair that has had a light mist of conditioning spray applied.

That is a huge difference.

Applying a light mist of a conditioning spray to dry hair before brushing is recommended as that will reduce the friction and seal the cuticle scales and therefore reduce the friction and damage.

And I think this is where the discussion went wrong….. The Yes side thinks -it’s not good to brush in a dry coat…..so this means that the No side is wrong when they say that it’s bad to brush a wet coat.
But the No side is talking about the damage from the stretching and the mechanical damage to the swollen cuticle scales.

If people had refrained from ridiculing the other side, groomers that don’t know the science would have had an opportunity to learn the correct science and a lot of drama could have been avoided.

So the next time you feel that some Instagram/Facebook drama is needed to increase your social media presence, maybe sit back, take a coffee and think – Are we really on the opposite sides? Does the industry need this drama? Or will a more balanced discussion benefit us instead and lead to a conclusion that we are actually on the same side.