Friday, 21 February 2014

Does co-washing really clean your hair? A scientific experiment!

Shampoo is designed to remove oil and dirt ( dirt in the form of particles, dust, lint etc stick to the oil coating on hair). In the process of doing this, shampoo can make hair feel dry. This effect has prompted some naturals to take up conditioner washing or co washing as it is popularly known and even go as far as just washing hair with water only. There are constant questions about whether co-washing or water only washing can actually clean hair. I therefore decided to crack my microscope out again in an attempt to answer this.

The Experiment

I used my own shed hair and imaged it:
-on its own without any washing
-washed with water only (5 minute wash and air dried for 4 hours)
-washed with conditioner only ( 2 minute water rinse, 2 minute conditioner wash, 2 minute water rinse and air dried for 4 hours)
- washed with shampoo only (2 minute water rinse, 2 minute shampoo wash, 2 minute water rinse and air dried for 4 hours)

The Results

1. Unwashed shed hair
I use a crazy amount of coconut oil because I like it, use it daily and swim and wash my hair 3 times a week. I knew before imaging that my hair would be the ideal oily hair sample because I have been imaging my hair for a while now! I did not add any additional oil to my hair prior to imaging (can you believe that!)

Unwashed super oily hair

My oily hair

2.Water wash only

Water washed hair actually seemed just to spread the oil more evenly over the surface of the hair. It really did not look any less oily than unwashed hair. I guess you may even say it is a good method to moisturise hair by spreading the oil evenly over the hair (oil rinsing perhaps?).

Hair washed with water only. An oily film is clear to see.

3. Co-washed hair
Conditioner washing cleaned hair to a pretty good level. Overall the thick oil coating of unwashed hair was gone. There were portions where you could see remnants of oil but I would say that 90% of the visible oil layer was gone.

Co-washed hair - within the circle are visible oil deposits

Co-washed hair - For the vast part, very free of the oil layer

4. Shampooed hair
Shampooing resulted in the cleanest hair with no visible oil deposits left on the hair strands.

Shampooed hair - oil free and super clean

Clean shampooed hair
I am pretty surprised that co-washing could actually provide a pretty decent level of cleaning. While, I was expecting some cleansing, I did not think it would be as good as it came out. I would however say that build up in the form of hair conditioner deposits is not visible under my microscope but can happen over time, so, even if you are a firm co-washer, the occasional shampoo will not do you any harm.

Shampoo remains the best way to cleanse oil from hair while water washing is pretty ineffective.

Additional notes:
Running warm water was used for all washes. In each wash or rinse,  hair was rubbed gently to simulate normal hair washing. Hair conditioner - L'oreal Eversleek Smoothing Conditioner, Shampoo - Herbal Essences Dazzling Shine Shampoo.

Please do note that under the microscope we can see oil layers but we do not see small deposits on hair e.g hair conditioner deposits (well you actually could see them with specialised instruments but not with my microscope!). Strictly speaking this experiment will answer the question, how well will washing method X remove oil from hair.

So which method are YOU going to choose to cleanse your hair ?


  1. In the winter moths, I use water only with a few bentonite clay mixes, since winter is REALLY harsh on my hair. In the summer times, more regular washes with powders. Has been working well for me this past year.

  2. Every since i started transitioning one thing i said i wouldn't do was co wash because i was never sure if it would clean my hair properly. I surprised it does and maybe i will give co washing a try.
    Maybe if you could explain the effect of having sulphate in your shampoo and weather it's good or bad.

  3. Awesome experiment! Thank you for doing it JC! I've always been a shampoo girl but as of late i've been throwing co-washing into the mix. I still always make sure that I do a good cleanse via shampoo or bentonite clay mix at least once a month. It's good to know co-washing cleanses more than i thought too! Idea: not sure if you've done this one already or not but compare shampoo to bentonite clay to see if cleansing properties are similar, if one is better or not, etc.

    1. It is a great idea. I have never purchased clays because I am wary of blocking my drains but this is a pretty good reason to do it! I also thought too about buying some silicone serums and seeing if co-washing on its own could remove the serum layer. Experiments! Yay!

    2. Excellent experiment ideas Milan and JC! I would also be interested in knowing how effective an ACV rinse is as well.

    3. Ditto that. Would love to see the experiment with a clay mixture.

  4. I'm very pleased you did that experiment.Thank you so much JC! Great post.It answered my doubts.

  5. Great post! I've wondered a lot recently if my hair would get clean with co-washing, and this helps answer that question.

  6. Great experiment!!! I can't do co washing because I feel like my scalp in still dirty when I use that method... But I'm glad it cleans the hair mostly!

    1. Yes, I was going to say, Too bad this doesn't show the effectiveness of conditioner on the scalp.

  7. I'm more concerned with how well conditioner cleans the scalp. I use very moisturising shampoos because they clean my scalp without making my hair feel dry and I actually like the feeling of having a lather. I also don't put anything but braid spray (basically water and glycerin) on my scalp and I found that since doing that my scalp never flakes from dryness and I never get product build up which I used to get. What are your thoughts on how effective conditioner is at keeping the scalp clean and not just the hair strands. Thanks! :-)

  8. My issue with co-washing is that it doesn't get the scalp clean. I realize that's a harder experiment to carry out, but I would be interested in any scientific information on whether it removes build up from the scalp.

  9. Thanks for sharing your experiment with us. I usually co-wash 3xs a month and shampoo once a month. Before reading your piece I was anxious in my thinking that I would have to change my routine.

  10. I may be wrong but I thought that the reason many people co washed is because they don't want all the oils to come off. They want to leave some in so their hair is never dry and they are never starting completely over. That is why I co wash. So to me, this proved that it worked. Pretty clean with a little bit of oil left.

    1. That's exactly why I do it, to leave some oil there! I think we have it for a reason. We are probably too obsessed with being squeaky clean in general. It's just a matter of finding routine that doesn't go too far one way or the other re: the oil. I do a combo of no/low detergent shampoo and co-washing, and I often must tweak the balance and frequency depending on hormones, weather/seasons/humidity, etc.

    2. Thank you for sharing your experiment, JC. I have been alternating between co-washing and washing my hair with African Black Soap (bar and liquid). I found that water alone was good to rinse my hair after working out or in the garden just after a hair wash - basically to rinse out any unseen bugs or plant debris). I co-wash my hair for 2 washings, then wash with the soap (i.e. shampoo). May hair does not do well with any sulfates, propylene glycol, or any other "chemical byproduct" or synthetic cleanser (they all dry my hair terribly). With one of the co-washes, I do a final rinse with ACV. This seems to really stimulate my scalp and my scalp feels clean afterwards. I wear locs. I stopped conditioning the full length of my hair and condition only the roots. To rest of my hair, I use a moisturizer that I put together using organic raw shea butter, organic raw cocoa butter, organic raw coconut oil, Jamaican Black Castor Oil, tea tree oil, and a little (very little) organic raw neem oil. My scalp and hair are thriving with this moisturizer.

      Even though the answer about co-washing cleaning the scalp is not clear; I find that co-washing works so much better for me than using a separate shampoo and conditioner. The co-wash that I use is by Shea Moisture and it includes a cleansers.

      So for now, I will stick with my current regimen.

      Blessings to all!

  11. wow, this was a great post, thanks for sharing! I wish I had a microscope.
    some girls also believe using conditioner on your scalp works as a milder cleaner, I think someone should experiment that too.

  12. This was a wonderful post. I have long been a skeptic about the thoroughness of co-washing but I can see that, while not perfect, it does do a pretty good job. Thank you for that. As others have stated, I would love to see the difference between clays and shampoos. Your voice is an important one in the blogosphere and I hope that you will continue to provide this scientific angle on natural hair and its care. Thank you so very much.

  13. Awesome post. Very interesting. For me it's cowashing and shampooing every other week.

    Abbi of

  14. Great Post! Well done experiment. I now know that it is okay to co wash once in a while. I swear by shampoo!

  15. I cowash during the winter, and find my hair is clean and my scalp is moisturized. Otherwise, if I shampoo every week during the winter, my hair is dry and my scalp is itchy. I low-poo/shampoo once every six weeks.

  16. Awesome Post. Makes so much sense.

  17. I have seborrheic dermatitis so I have to use an actual cleansing product on my scalp. My hair, on the other hand would love it if it never saw shampoo or a cleasing conditioner again. I'm curious to see the results when you repeat the experiement with silicone. However, I'm even more curious to find out how you're able to wash your hair 3 times a week given your texture and length. I presume that you don't do WNG's but I beg beseech and implore you to share how that is possible for you. My dermatologist is always encouraging me to wash more than once a week but I don't think that I have the time. Thanks a bunch.

  18. Great article! I like the others also wonder about the scalp issue. I have a very itchy scalp and shampoo is the only thing that calms it down a little bit. Thanks!

  19. Hi, I wondered that if any studies have been done on co washing and its effect on the scalp. i have heard to clogged follicles and hair shedding due to the chemical and repeated massaging causing the roots to soften and fall out?

  20. Thanks for this, JC; quite informative. It definitely confirms the experience I have when I've tried each of these methods to cleanse my hair:

    Water: nothing but a more intensified, yucky feeling (because the hair stays oily)

    Co-wash: relatively clean (I even see the dirty water run from my hair into the tub, ewww... but at least that tells me that it's definitely washing out the product buildup). BUT, if I've used my shea butter mix (shea butter + various oils) heavily during that week between wash days, then my scalp & hair strands will NOT get completely clean with just co-washing (because I'll still feel the shea butter when I touch my freshly co-washed hair)

    Shampoo: A must-have; gets rid of everything (clarifying shampoos are even better at this than regular moisturizing shampoos)

    From my experience, it has been best for me to shampoo wash one week & then co-wash the following week. I was 1x per week, so alternating between these two methods has helped me find a nice balance between maintaining moisture and having clean hair &scalp.


  21. Wow! I loved this....sharing!

  22. Many hair, what do u do to get rid of sweat and pollution from hair when u wash only once a week. I travel a lot and at the end of the day I feel I need to wash my hair like I shower daily to clean my body as both get equally dirty. How do I get rid of sweat and dirt from the hair daily without washing it. The dry shampoo just makes it look nice but it does not remove any dirt.


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